Carrera - Removing Engine Compartment Heater Blower

[dshepp806]

Yes, scarcellar and mysterytrain nailed this one long ago....old news but still good stuff!! Thanks!



Best,

Doyle

[scarceller]

Originally Posted by Bearded Viking

Ran into a snag this morning...

Got in the car this morning, lifted the heater levers and turned the center knob. The footwell blowers started up. All was fine, then I smelt an electrical smell, and turned the knob off, but the right footwell fan kept spinning (low speed) and the left one does not appear to be working at all. I turned the car off and disconnected the heater relay for now. Did I fry the glass reed when I soldered the jumper, but that would not seem to matter since I jumpered it. Has anyone else encountered this issue?

The footwell blowers, heaters levers and heater knob worked fine before i did this mod.

The footwell blowers are wired in Parallel so if one runs and the other does not you have a new problem that is most likely not related to the relay mod. My guess is that the left foot well blower is frozen, this is very common problem. Remove the left blower and try turning the Squirl Cage by hand to see if it is frozen. Let us know what you find.

[Bearded Viking]

Sal, you hit the nail on the head. I just replaced the driver side footwell blower (yep, lubed the felt before installing) a month ago, but because it's used, it has hard time rotating on a cold morning. The fuse popped on the left side foot blower due to this mod causing the footwell blowers to slowly move even with the levers down on the center knob set to 0. I guess in the morning I'll have to set the heater on high in order to spin the blowers to a faster speed.

[scarceller]

Originally Posted by Bearded Viking

Sal, you hit the nail on the head. I just replaced the driver side footwell blower (yep, lubed the felt before installing) a month ago, but because it's used, it has hard time rotating on a cold morning. The fuse popped on the left side foot blower due to this mod causing the footwell blowers to slowly move even with the levers down on the center knob set to 0. I guess in the morning I'll have to set the heater on high in order to spin the blowers to a faster speed.

One other issue with these blowers is that they get real HOT 150 deg or more. The heat is in direct contact with the squirl cage and in my car the cage got so hot that it sofented and then the cage slid down on the shaft (remember the motor is on the bottom cage on top, they are mounted vertical) once the cage slid down enough it started to rub on the housing which in turn developed even more heat at the lower rim of the squirl cage where it was rubbing and the end result was the squirl cage fused (melted) to the housing! I had to really pry the cage away from the housing then remove the cage from the shaft clean the shaft and epoxy the cage further up on the shaft. I also greased the motor a little and all is well now.

I'm simply amazed that these motors have lasted 25 years with the heat they carry.

Here's an old thread on this issue:
Footwell blower repair

[Bearded Viking]

That's exactly what happened to the driver side blower I removed a month ago. The fan was fused to the housing! Is it normal for the footwell blowers to spin a little with the lever down and the center knob set to 0? Thanks again Sal!

The Viking

[scarceller]

Originally Posted by Bearded Viking

That's exactly what happened to the driver side blower I removed a month ago. The fan was fused to the housing! Is it normal for the footwell blowers to spin a little with the lever down and the center knob set to 0? Thanks again Sal!

The Viking

With the relay modified to jumper the reed switch, if the red levers between the seats are down then the relay should NOT be activated. Meaning pin 4 should be 0volts (see schematic in post #2). Simply, the red levers tell the relay to come on and this delivers the 12volts out pin #4 if the levers are pulled up.

Then pin #4 delivers the 12v to the 3 pos. rotary switch which powers the blowers. Pos #1 feeds through 2 large resistors to achieve low speed. Pos #2 feeds through only 1 resistor to achieve med. speed. Finally pos #3 activates yet another seprate relay to achieve hi speed. So pos #3 directly feeds 12 volts to the blowers while pos 1 & 2 place resistor(s) in series with the blowers.

So the short answer is the blowers should not see ANY voltage if the levers are down. They also should not see voltage if the levers are up and the rotary switch is set to pos #0. Or the inverse, the motors should only get power if red levers are up and rotary switch is in pos 1, 2 or 3. Hope this makes sense.

Now, if the engine is running you may have air flow through the blowers causing them to spin (without any voltage). The best way to test this system is with 'key on' RUN pos. engine off.

So if the red levers are down and you have blowers running with engine off and key in RUN you have an issue that needs investigation. You could have created a solder bridge when you jumpered the reed switch, be sure you only jumpered the reed switch and did NOT somehow solder something else closed (bridged) in the process. A picture of the solder job would be very helpful.

[Bearded Viking]

OK, problem solved! The used driver side blower motor was not as good as I thought, I exchanged it for another and now everything works as expected. Levers down and center knob off, no fans spin now. Thanks for the helpful replies Sal!!!

[scarceller]

Originally Posted by Bearded Viking

OK, problem solved! The used driver side blower motor was not as good as I thought, I exchanged it for another and now everything works as expected. Levers down and center knob off, no fans spin now. Thanks for the helpful replies Sal!!!

Glad everything works as it should and your relay mod had good results. Enjoy your new heat.

[notmytarga]

It's August for Pete's sake - why are we worried about heat???

Here is my question: Does the rear blower run with the levers down , ignition ON but engine not started?

My rear blower was stuck by a chunk of metal in the cage area and now I have it running but the levers don't seem to control it. I can't start the engine because I'm in the middle of a oil cooler/lines install. Will the levers control it once the engine starts? I looked over the Factory wiring diagram for 1975 and didn't see any of the heater control module type stuff - may explain the 'advanced' control.

[scarceller]

Originally Posted by notmytarga

It's August for Pete's sake - why are we worried about heat???

Here is my question: Does the rear blower run with the levers down , ignition ON but engine not started?

My rear blower was stuck by a chunk of metal in the cage area and now I have it running but the levers don't seem to control it. I can't start the engine because I'm in the middle of a oil cooler/lines install. Will the levers control it once the engine starts? I looked over the Factory wiring diagram for 1975 and didn't see any of the heater control module type stuff - may explain the 'advanced' control.

First, what yesr car are we talking about here? 1975?

If I recall correctly the 75 car always has the rear blower running, I will double check once you let me know what year car you have.

This thread was for the 84-89 Carrera cars.

[LeeH]

Just curious... what are the electrical ramifications of the modification if someone reattaches the rear blower?

[DCinVA]

I believe this solution was tracked down by MysteryTrain, so lets give him some credit. There are pages and pages of posts about it that provide interesting reading. I used this solution to fix my 86. In addition, instead of spending $250 to replace the rear blower, I used a $20 motor sourced from Grainger to replace the rear blower, I had to do the reed switch mod because the grainger motor draws a different amount of current, and was not triggering the reed switch to allow use of the from blowers.

LeeH - No electrical ramifications, you can run the rear blower with this mod. In fact I would suggest that the rear blower is a somewhat important part of the cooling system (at least on the 3.2's that I am familiar with). There is an engine temp switch that turns on the rear blower to help cool things down if the engine gets too hot. I suppose you can get by without it, but cool is good, hot is bad. You decide.

[scarceller]

OK, so I got to thinking about this heat controller mod to allow the front blowers to run without the rear.

How would you like to run those front blowers safely without the controller at all?

The stock controller had some very fancy functions for the rear blower but if you just removed the rear blower then who cares about those fancy functions?

So what special function does the controller have for the front footwell blowers? The only thing I see is that it turns ALL blowers off while you are CRANKING during startup.

If this is all we care about then there is one more way to run the front blowers without the rear. I have come up with a way to take out the Heat Controller completely and simply replace it with a simple relay.

I'll write it up if folks are intrested, it's very easy and no wiring harness changes needed, you simply wire the new relay to the controller's stock harness connector.

You can even go a step further and replace that expensive controller with 2 relays and run the rear and footwell blowers safely. But you'd give up a few rear blower features.

[DCinVA]

I would be interested in that solution. I am currently using my rear blower, but.....

[scarceller]

Here are the details for replacing the entire Heat Controller with 2 simple relays:



If you did a heat backdate and no longer have rear blower you only need Relay #1.

If your heat controller burned out and you want a cheap alternative then use both relays.

This setup is electricly safe but does come with some trade off:
1. The front footwell blower function is independant of the rear blower, meaning the front blowers will work even if the rear is not working. The stock controller will not allow this.
2. The stock controller also has the ability to command the rear blower 'ON' if it detects a engine 'HOT' condition while in stopped traffic. This is done to cool the heat exchangers with fresh air. Keep in mind that if you did a heat backdate and have already removed the rear blower you have given this up anyway. Also, if you whish to achieve this same thing you simply pull up slightly on the 'Orange Heat Levers' between the seats and this will command the rear blower 'ON' even with this alternative relay approach.
3. The stock controller shuts off power to the blowers while the key is in 'START' and the engine is cranking, this alternative does NOT give this up, it still has this feature.

The other good thing is that you can use stock Bosch 'BLACK' relays for this.

The best way to wire this up is to get a BAD controller and simply rip the electronics out and keep the case and the plug, then solder the new relay harness to the controller plug. OR - you could find male spades that fit into the stock harness. The idea is NOT to alter the stock harness connector for the stock controller.

Our host sells the relays 911-615-109-01 and the sockets 901-612-333-00, socket is kind of pricey but you could simply use these type relays as well http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=260282324633

Good Luck.

[scarceller]

UPDATE:

I was cleaning up the rear engine bay and decided to get rid of the heat controller, I replaced it with 2 relays. I wired up sockets for both relays but only installed 1 because I do not have the rear heat blower since I backdated my heat. But I figured to still have the wire harness support running the rear blower in the future.

Here's the final Schematic used for this:


This circuit covers the basics:
1) allows front blowers to run without the rear installed.
2) turns blowers off while in 'START' cranking mode.
3) will turn on only the rear blower if the engine gets hot and the engine temp switch closes.

What it does not do:
1) ignores the speedometer signal, I have NO clue what this was used for. But I think it was part of deciding when to turn on/off the rear blower if engine is very hot.
2) no longer prevents the front blowers from running without the rear.

Wiring this thing up, you have 2 choices:
1) rip apart a stock Heat Controller, take out it's insides and simply keep the plug end and wire the 2 relays and the diode to this plug. This approach will let you do this mod with NO alteration to the stock harness.
2) I did this one: cut the stock harness connector and simply solder and shrink tube the 2 new relay plugs to the stock wiring. This one is more complicated as it's hard to work in that tight space and the stock harness is not very long to begin with.

And YES I have a spare (no longer needed) stock heat controller that is modified to run the front blowers without the rear. I'm willing to sell it if someone wants it, I can easily put it back to stock configuration as well if need be. Check the For Sale section as I have it listed.

[Jaskas]

Hi!
I´ve been battling with my heating system of my 87-model with auto heat.

Problem: The footwell blowers wont work

Allready tried:
- Checked all fuses (engine/luggage kompartment and the ones by the blowers)
- Switched foglights / footwell relays
- Did the reed swich jumper fix
- Checked that blowers really work with straight current to them

Sooo, where could the problem be? Im running out of option myself...

[scarceller]

Originally Posted by Jaskas

Hi!
I´ve been battling with my heating system of my 87-model with auto heat.

Problem: The footwell blowers wont work

Allready tried:
- Checked all fuses (engine/luggage kompartment and the ones by the blowers)
- Switched foglights / footwell relays
- Did the reed swich jumper fix
- Checked that blowers really work with straight current to them

Sooo, where could the problem be? Im running out of option myself...

Up a few posts you will see the schematic showing the heat controller relay harness pins:
- be sure you have 12v at all times on pins 3, 7 and 8.
- Then pin 12 should have 12v with key in 'RUN'.
- pin 2 must be ground at all times
- pin 9 is the pin that goes to ground to activate the heat controller, I'm not sure about the auto-heat setup but in the non-auto-heat this pin 9 is pulled to ground when you lift up on the orange levers. I'm sure that in the auto-heat it also is grounded by the autoheat system. When this pin 9 goes to ground it will cause pin 4 to go 12V which is the line that feeds the front blowers.

Another quick test is to unplug the heat controller from the harness and hot wire 12V to pin #4, this should send the power up to the front footwell blower rotary switch, if the switch is in pos #3 and pin 4 has 12V the blowers should run.

[85carrera]

I think you guys problem is that you haven't moved to a warmer climate yet. I don't use my heat. sorry that was mean. well, in fact if you do end up moving to a warmer climate then you have to deal with the A/C. Even worse than dealing with heat issues.

good luck figuring it out....

[Jaskas]

Originally Posted by scarceller

Up a few posts you will see the schematic showing the heat controller relay harness pins:
- be sure you have 12v at all times on pins 3, 7 and 8.
- Then pin 12 should have 12v with key in 'RUN'.
- pin 2 must be ground at all times
- pin 9 is the pin that goes to ground to activate the heat controller, I'm not sure about the auto-heat setup but in the non-auto-heat this pin 9 is pulled to ground when you lift up on the orange levers. I'm sure that in the auto-heat it also is grounded by the autoheat system. When this pin 9 goes to ground it will cause pin 4 to go 12V which is the line that feeds the front blowers.

Another quick test is to unplug the heat controller from the harness and hot wire 12V to pin #4, this should send the power up to the front footwell blower rotary switch, if the switch is in pos #3 and pin 4 has 12V the blowers should run.

Thanks. I will try those trick out today! ( I have no other life than Porsche in Sweden )