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help! 88 heating system nightmare

Hi all!

I am here in NYC and I have 2 911's, a 9974s and 88 Carrera. Both have their own issues.

I've had the 88 for about 2 years, and about a year ago had a full engine reseal and bunch of other stuff done.

Now, the one thing I haven't had time to tackle, is the heating/cooling system. This thing is too complex for me to figure out, and the local shops that I use shrug at the site of the car.

So I'll start with my highest concerns first, and go down the list from most important to least.
1. The heat comes from the driver side vents when driving. The lever in the middle is pulled into close position. I checked the little baffle under the car, and it is operational. When I open the red lever, I get a lot more heat through the vents, but when I close it, there is still heat coming. On the passenger side it's just outside breeze that comes in. Is there another baffle anywhere else? Any ideas?

2. The heater blower motor. I have no heat (besides the levers that just guide the hot air). I had a local shop give the motor power, and the motor works. So my first thought was that little relay in the engine compartment. So I went on eBay, found a guy that had a bunch of used ones (I think he has a race shop)... so he sent me one ($100 value), and it didn't work.. so he sent another, same story. So I already tried 6-7 of them, and none work. So even though they are used, I figured at least one of them would work. I then took out the passenger seat, and looked at the little box between the seats. I don't see anything out of place, but then again, I'm not sure what I'm looking at, but it looks fine. I also replaced the fuses in the footwell blowers. Could that little box be broken? Anything else I need to check? Any other fuses? Any ideas?

3. Fresh air blower... so it worked when I bought the car, but made a bad sound and sounded tired. Then one day it stopped working. I see a lot of different replacement parts for the fresh air system, but I'm not sure what I need to get this fixed.

I would appreciate the help with this, as I'm out of ideas, and no shops are near by. The one p shop I know, is an hour and a half away, requires $50 in tolls, +gas, plus I need to leave the car, so I would need to uber, which is $120 each way... anyway... I'm on my own here, and I'm not very skilled with this.
Old 06-19-2019, 01:13 PM
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Fresh air blower start here https://m.youtube.com/watch?v=p3ik9Bo69D0
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Old 06-19-2019, 06:11 PM
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The heat system on these cars is ridiculously complex. Is yours the manual or autoheat system? There are posts on diagnosing and repairing them on the forum, as well as posts on how to modify a non functioning relay to function (though I doubt all the ones you had were bad).

Do you have the schematics for the electrics? Do your footwell blowers work?
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Old 06-20-2019, 05:08 AM
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" I'm on my own here, and I'm not very skilled with this."

If you're new to working on these cars the Bentley service manual is a 'must have.' It covers most everything in the car, including a troubleshooting guide to the heat and ventilation. You can get a copy from Amazon.

The Bentley will also help you identify components which will make it easier for you to ask questions here.

Good luck!
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Old 06-20-2019, 05:43 AM
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Mine has worked well for years with the manual heat and the van fan. It's worth the trouble and expense to get it functioning. You also have two footwell blowers that boost the heat flow when you turn the rotary dial between the seats from 0 to 1 to 2 to 3 assuming you have manual heat. However, the two red levers should provide variable fan speed as you raise them from full down to full up. There are electrical contacts on those levers that, when raised, turn on the heater fan in the engine compartment. If your heater fan motor isn't turning on when you raise the red levers, you have an electrical contact issue with the red levers. Additionally, just raising and lowering the levers will provide heat flow even if the heater fan motor isn't working (either because it's fried, or the red lever electrical contacts are fried thus not signaling the engine heater fan to turn on). Raising the red levers opens the heater boxes under the car and as you drive faster and faster, more air flow comes in. Bottom line, get the electrical contacts at the red levers working which should signal the engine heater fan to turn on and provide you variable heat flow. Once you have both red levers working with variable heat flow, then get your rotary 0-1-2-3 dial between the seats working which controls the footwell blowers located in the kick plates by the passenger's right foot and left of the clutch pedal on the driver's side. The 1 setting is almost imperceptible in boosting the heat flow. The 2 setting is a little better. The 3 setting is definitely noticeable.

Now, on your HVAC panel to the left of your radio, move the red lever to direct the heat outflow. You can set it to the full right or full left which would direct 100% of the heat to either your feet or to the windshield defrost. Or, you can set the red lever anywhere in between full left or full right for variable feet heating or windshield heating. If you need more flow, turn your footwell blowers on setting 1, 2, or 3 to boost heat flow. It's quite an effective heater and defroster when you have the engine heater fan and both footwell blowers working.

For the vent fan, sounds like it's dead and needs replacing. Once you get that replaced, you have three controls to worry about. On your HVAC panel on the upper right middle you have a lever. That lever turns on your vent fan and is a multi-position lever that allows for increasing vent fan flow the further right you slide it.

However, and very importantly, the lever on the top left of the HVAC controls whether that flow makes it to your interior. If the lever is full left, even with the upper right lever full right for max fan speed, it won't let any airflow in. So, move that upper left lever to the right and it will allow that vent fan air to flow to the interior.

Next, use the lever above the red heater lever to direct your vent fan output to your feet or to your windshield or variable anywhere in between.

Another feature is with your vent fan and heater fans off, if you move the upper left black lever to the right until it's touching the upper vent fan speed control lever, outside air can flow in without activating the vent fan. However, if you are going to use the air conditioning in your car, ensure this upper left black lever is full left or else you will be allowing outside hot air to flow into your car and it will be fighting the air conditioning.

Good luck, when you get it all working, it is a very effective system. If you don't have working A/C, I have had a Griffith's system since 2008 and it is perfect in the Alabama summer.
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Last edited by pavegeno; 06-20-2019 at 06:44 AM..
Old 06-20-2019, 06:39 AM
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Quote:
Originally Posted by Jack Stands View Post
The heat system on these cars is ridiculously complex. Is yours the manual or autoheat system? There are posts on diagnosing and repairing them on the forum, as well as posts on how to modify a non functioning relay to function (though I doubt all the ones you had were bad).

Do you have the schematics for the electrics? Do your footwell blowers work?
It is manual.

From my understanding, if the blower in the back is not working, then the footwell ones won't work. So I can't tell if they work. I have replaced the fuses there (they were busted), so I assume they should work.

no schematics
Old 06-20-2019, 08:19 AM
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Read the owners manual. It is really real simple.

The main thing to remember, the fresh air, heat, and AC are three distinct systems, and it easy to run all three systems at the same time. I doubt any other car on the planet has that ability. For sure no modern car can.

If you want AC, make sure the levers on the fresh air are all to the left and the heat levers are down.

If you want heat, pull the levers, and obviously make sure the AC of off, and the red lever is to the left for heat on your feet, to the right for heat to the windshield. Make sure the other levers on the dash for fresh air are to the left.

The fresh air system is way worse than the AC. It will not blow in your face, just to your feet, or the windshield. Almost useless.
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Old 06-20-2019, 08:22 AM
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Quote:
Originally Posted by pavegeno View Post
Mine has worked well for years with the manual heat and the van fan. It's worth the trouble and expense to get it functioning. You also have two footwell blowers that boost the heat flow when you turn the rotary dial between the seats from 0 to 1 to 2 to 3 assuming you have manual heat. However, the two red levers should provide variable fan speed as you raise them from full down to full up. There are electrical contacts on those levers that, when raised, turn on the heater fan in the engine compartment. If your heater fan motor isn't turning on when you raise the red levers, you have an electrical contact issue with the red levers. Additionally, just raising and lowering the levers will provide heat flow even if the heater fan motor isn't working (either because it's fried, or the red lever electrical contacts are fried thus not signaling the engine heater fan to turn on). Raising the red levers opens the heater boxes under the car and as you drive faster and faster, more air flow comes in. Bottom line, get the electrical contacts at the red levers working which should signal the engine heater fan to turn on and provide you variable heat flow. Once you have both red levers working with variable heat flow, then get your rotary 0-1-2-3 dial between the seats working which controls the footwell blowers located in the kick plates by the passenger's right foot and left of the clutch pedal on the driver's side. The 1 setting is almost imperceptible in boosting the heat flow. The 2 setting is a little better. The 3 setting is definitely noticeable.

Now, on your HVAC panel to the left of your radio, move the red lever to direct the heat outflow. You can set it to the full right or full left which would direct 100% of the heat to either your feet or to the windshield defrost. Or, you can set the red lever anywhere in between full left or full right for variable feet heating or windshield heating. If you need more flow, turn your footwell blowers on setting 1, 2, or 3 to boost heat flow. It's quite an effective heater and defroster when you have the engine heater fan and both footwell blowers working.

For the vent fan, sounds like it's dead and needs replacing. Once you get that replaced, you have three controls to worry about. On your HVAC panel on the upper right middle you have a lever. That lever turns on your vent fan and is a multi-position lever that allows for increasing vent fan flow the further right you slide it.

However, and very importantly, the lever on the top left of the HVAC controls whether that flow makes it to your interior. If the lever is full left, even with the upper right lever full right for max fan speed, it won't let any airflow in. So, move that upper left lever to the right and it will allow that vent fan air to flow to the interior.

Next, use the lever above the red heater lever to direct your vent fan output to your feet or to your windshield or variable anywhere in between.

Another feature is with your vent fan and heater fans off, if you move the upper left black lever to the right until it's touching the upper vent fan speed control lever, outside air can flow in without activating the vent fan. However, if you are going to use the air conditioning in your car, ensure this upper left black lever is full left or else you will be allowing outside hot air to flow into your car and it will be fighting the air conditioning.

Good luck, when you get it all working, it is a very effective system. If you don't have working A/C, I have had a Griffith's system since 2008 and it is perfect in the Alabama summer.

Thank you very much for such a detailed response. It is a manual system.

ok, so question about the red levers. How do I get to those contacts? how to fix them, if they are broken (just sand them?)? When I raise the levers, heat into cabin comes in when I'm driving. When I'm stationary, barely any (if any) heat comes to the windshield.
This year, I noticed that regardless of the position of the levers, heat comes in through the drivers side (almost at the speed of fresh air going into the cabin, as compared to the passenger side, which has cool outside air coming in). When I open the levers, a lot more heat comes in. Do the exhaust/heater boxes have an internal valve that is controlled by the red levers? The outside flappers do open and close via the levers.

When I engage the dial, nothing happens. I have replaced the fuses in the footwell motors (they were bad), but they don't engage. I read somewhere, that they only engage when the rear motor engages. I had a shop test the rear motor, it works.

I have factory AC, but I haven't filled it yet, so don't know if it works (when I engage, it blows, but obviously its not filled up).
Old 06-20-2019, 08:34 AM
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Quote:
Originally Posted by EuroZ06 View Post
So I'll start with my highest concerns first, and go down the list from most important to least.
1. The heat comes from the driver side vents when driving. The lever in the middle is pulled into close position. I checked the little baffle under the car, and it is operational. When I open the red lever, I get a lot more heat through the vents, but when I close it, there is still heat coming. On the passenger side it's just outside breeze that comes in. Is there another baffle anywhere else? Any ideas?
Thought I'd chime in on this issue -- there should be two separate baffles under the car, each controlled (opened/closed) by the corresponding red lever by the parking brake -- these baffles can get corroded/rusted and stop closing correctly -- sounds like the driver's side baffle isn't closing completely and is still letting some of the hot air generated by the heat exchanger into the cabin. Have you checked/confirmed operation of each of these baffles?

Here's another thread on this topic that could be helpful -- note that folks generally refer to the baffle as a "flapper box" Heater flapper box
Old 06-20-2019, 08:36 AM
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ok, I figured out why I get hot air. The heater box has flappers, and a valve thingy inside. I was just looking at the outside flappers. I need to see what's going on with that inside valve and see if I can give it grease, or adjust, or buy new box.

I'll take a look at fresh air blower. It's $100 here on pelican, so I might as well just buy one and replace it, since it doesn't work.

So the red levers should activate the blower in the engine compartment. However, when the car is not moving, very little heat comes out, when you start moving, a lot of heat comes out. Is that by design? Also, if I have ignition on (engine off), and engage the levers, would that engage the motor?

So the switch between the seats controls the footwell motors? Do I need to move the HVAC control to the bottom for them to engage? when car is stationary, should I feel the hot air blowing out of them? Once again, when I drive, and pull the red levers into "on" position, the HVAC control directs hot air to either defrost or to the foot well (its blowing hard), but when I'm stationary, nothing...
Old 06-20-2019, 09:45 AM
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Quote:
Originally Posted by EuroZ06 View Post
ok, I figured out why I get hot air. The heater box has flappers, and a valve thingy inside. I was just looking at the outside flappers. I need to see what's going on with that inside valve and see if I can give it grease, or adjust, or buy new box.

I'll take a look at fresh air blower. It's $100 here on pelican, so I might as well just buy one and replace it, since it doesn't work.

So the red levers should activate the blower in the engine compartment. However, when the car is not moving, very little heat comes out, when you start moving, a lot of heat comes out. Is that by design? Also, if I have ignition on (engine off), and engage the levers, would that engage the motor?

So the switch between the seats controls the footwell motors? Do I need to move the HVAC control to the bottom for them to engage? when car is stationary, should I feel the hot air blowing out of them? Once again, when I drive, and pull the red levers into "on" position, the HVAC control directs hot air to either defrost or to the foot well (its blowing hard), but when I'm stationary, nothing...
No, at least not in my 1985. The red lever on the dash is only to change the place that the heat blows. Left is the floor, right is the windshield or defroster.

You have to pull up the red handles on the floor, next to the parking brake to get heat.

Maybe the real issue is your car is up on the ceiling!
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Old 06-20-2019, 10:44 AM
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1) good on the flapper box issue, that seems to be the most important issue to resolve as summer solstice approaches

2) fresh air blower -- gotta say, in all the years I've had my '86 Carrera I've never though "wow, good thing my fresh air blower works, it would really suck if it was broken . . . ." -- the fresh air blower only pushes air through the defrost and heater vents -- not really sure why it's there in the first place? I'd personally let it sit broken -- unless you're talking about the AC blower fan (which blows air conditioned air out of the dash vents (only)

3) red levers (between seats) both open the flapper valves to let heat into heating system AND activate the trunk and footwell blowers. As originally delivered, 911s heat was delivered/controlled solely by the flapper valves, with little hot air coming through until the car started moving. Sounds like, notwithstanding the fans being inoperable, you're witnessing proper operation of this passive system when you pull up the levers (but that pushing down the levers isn't causing one of the flapper valves to completely close.

4) the switch (knob) between the seats controls how fast the footwell blowers spin -- the footwell blowers should only work when the red levers between the seats are pulled up and should turn off when these levers are pushed down -- you control where the footwell blowers send the heated air with the bottom lever on the dashboard control -- all the way to the right sends heated air to the defroster vents, all the way to the left sends heated air to the heater vents below the dash -- center sends heat to both -- you'll know if the footwell blowers are working, as they make some real noise (especially in the high setting)
Old 06-20-2019, 10:48 AM
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Originally Posted by darrin View Post
1) good on the flapper box issue, that seems to be the most important issue to resolve as summer solstice approaches

2) fresh air blower -- gotta say, in all the years I've had my '86 Carrera I've never though "wow, good thing my fresh air blower works, it would really suck if it was broken . . . ." -- the fresh air blower only pushes air through the defrost and heater vents -- not really sure why it's there in the first place? I'd personally let it sit broken -- unless you're talking about the AC blower fan (which blows air conditioned air out of the dash vents (only)

3) red levers (between seats) both open the flapper valves to let heat into heating system AND activate the trunk and footwell blowers. As originally delivered, 911s heat was delivered/controlled solely by the flapper valves, with little hot air coming through until the car started moving. Sounds like, notwithstanding the fans being inoperable, you're witnessing proper operation of this passive system when you pull up the levers (but that pushing down the levers isn't causing one of the flapper valves to completely close.

4) the switch (knob) between the seats controls how fast the footwell blowers spin -- the footwell blowers should only work when the red levers between the seats are pulled up and should turn off when these levers are pushed down -- you control where the footwell blowers send the heated air with the bottom lever on the dashboard control -- all the way to the right sends heated air to the defroster vents, all the way to the left sends heated air to the heater vents below the dash -- center sends heat to both -- you'll know if the footwell blowers are working, as they make some real noise (especially in the high setting)
HA! you are probably right about the fresh blower lol. But, you know, I'd like for everything to work. So maybe I'll work on it at some other time. Maybe I'll dig into it, and just see if something came loose.

Ok, the HVAC lever does change the direction of air, foot or windshield.

The levers between the seats then probably make the engine motor work (is there a way to check that?). So my footwell motors are not working then. Or perhaps the knob is not working? I do not see any change in operation when I turn the knob. I do not hear any fans engaging when I twist it. I have replaced the fuses that are in line with the footwell motors. What else can I check? how do I check if it's the knob or the motors?

When I turn on AC, it blows air, as it should... except its not cold air. I have no idea if there are any leaks in the system, since I haven't tried filling it up (well I did, but it was via one of those cheap bottles... which didn't work).
Old 06-20-2019, 11:45 AM
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1) I hear you on the fresh air blower, would suggest you prioritize it below the heat and AC for now.

2) I've owned my Carrera for around 20 years and have replaced my footwell blowers several times -- they use motors/bushings that deteriorate/fail over time -- not clear whether you've powered the footwell blowers up independently to confirm that they both work -- blown footwell blower fuses would point to seized footwell blower motors (or very squeaky footwell blower motors that are creating too much resistance and blowing fuses) -- believe that a failed footwell blower OR a failed trunk blower motor will take the entire circuit offline, which could explain why your replacement relays didn't work.

3) AC -- is a whole other can of worms -- shortish version -- even when new, our cars' AC was marginal at best. Further, the hoses carrying the freon are all gas-permeable, allowing the freon to slowly leak out (and then blow warm air) -- this caused me to abandon my AC when I moved from the east coast to Denver many years ago. I'm now in the process of getting my AC operating again, but this is requiring me to a) replace all the hoses with new, non-permeable hoses, b) replace the compressor (my trunk deck had a oil stain just above the compressor belt, indicating the compressor's seal had worn out), and c) replace virtually every other part save the front and deckled condensers -- My mechanic is using parts from www.griffiths.com for this (and will be converting my car from generally NLA r-12 freon to r-134a) that should make my AC slightly more effective than new. Others on this board have a LOT of good things to say about Griffiths (and forum user Keuhl is also the owner (?) of Griffiths) and Griffiths has options available (rear wheel well condensers, etc.) that can significantly increase our cars' ac cooling capacity -- There's also another 911-specific option available from a forum member/vendor out of the UK that totally ditches the engine-driven compressor and is electrically driven -- either way, point here is that unless your AC system's already been recently upgraded and gone through, it likely will need professional help (and $$$) to get working/effective.

So, at the end of the day, you're in a situation similar to mine a few years back -- I was able to get/keep my heat working (which was crucial to cold weather driving/defrosting windshield/etc.) but used "nature's AC" (opened a window/popped of targa top) on hot days, but with some $/time I'm finally tackling my AC

Last edited by darrin; 06-20-2019 at 12:59 PM..
Old 06-20-2019, 12:57 PM
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Quote:
Originally Posted by EuroZ06 View Post
HA! you are probably right about the fresh blower lol. But, you know, I'd like for everything to work. So maybe I'll work on it at some other time. Maybe I'll dig into it, and just see if something came loose.

Ok, the HVAC lever does change the direction of air, foot or windshield.

The levers between the seats then probably make the engine motor work (is there a way to check that?). So my footwell motors are not working then. Or perhaps the knob is not working? I do not see any change in operation when I turn the knob. I do not hear any fans engaging when I twist it. I have replaced the fuses that are in line with the footwell motors. What else can I check? how do I check if it's the knob or the motors?

When I turn on AC, it blows air, as it should... except its not cold air. I have no idea if there are any leaks in the system, since I haven't tried filling it up (well I did, but it was via one of those cheap bottles... which didn't work).
When you raise either or both red levers, the engine compartment heater fan should come on. You can do this with the key in the run position without the engine on so you can hear the motor. Just lift the red levers and the heater fan should come on. If not, you have an electrical continuity issue between the levers and the blower since you said the blower motor works if you apply electricity directly to it.

The footwell blowers will only work if you raise the levers and then turn the knob. If the engine compartment blower motor doesn't work with the red levers up, you can't diagnose or confirm whether your footwell blowers are working until you get the engine compartment fan working when you pull up on the red levers. (Of course you could remove them and bench them directly like the engine compartment fan, but that is extra work.) Once you do get the engine compartment fan working, just turn the knob to position "3" with the red levers up. There will be no question about whether they are working because they sound like a jet engine, Me-262 to be exact, and it is awesome and loud!

For your a/c, read Griffith's "Mr. Ice Project" at https://griffiths.com/mr-ice-project/
I did this in 2008. Best $4500 I have spent on my 911 living in the south. I ordered the complete system replacing every a/c component and had my dealer install it who had done several. I have modern a/c that keeps my cab cold in the southern summer and I have to turn the fan and temperature down to avoid getting too cold even in stop and go traffic in the summer.

good luck!
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Last edited by pavegeno; 06-21-2019 at 05:58 AM..
Old 06-21-2019, 04:02 AM
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Since you don't have auto heat, you have the four position rotary switch between he seats labeled 0, 1, 2, and 3.
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Old 06-21-2019, 04:08 AM
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That graphic is not accurate for my 85. I can't get heat from the AC vents at any time. Only AC blows out the AC vents. I suspect they (Porsche) changed it later since that graphic says 86 to 89 models.

The fresh air is mostly a joke. The only time I use it is at an autocross, full fan speed blowing some on the floor, and some on the windshield at an autocross, just to get more air into the car. I rigged up a switch to disable the compressor, so I can turn on the AC system and have that air blow on me, even if the compressor is not running.

Air blowing on my face is helpful. Our autocross rules and any track day is no AC usage. They don't want water dripped on the track for other cars to drive through.
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Old 06-21-2019, 05:37 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
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Little known fact, the engine compartment blower heater blower motor will also come on if the engine starts to get very hot and it helps cool the engine. I don't know what drives it to come on (engine oil temp or some internal sensor), but it has happened a few times over the course of owning the car living in the south.

EDIT: Here is a link. Another good reason to ensure your engine compartment heater blower motor is working if you live in a hot area. Running fan after engine is turned off?
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Last edited by pavegeno; 06-21-2019 at 06:06 AM..
Old 06-21-2019, 06:00 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
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