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Wayah Road Warrior
 
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Help with 930 Heating Problem (Footwell Blowers)

87 930 with Automatic Heat Control

Left footwell blower has not workd for the past year. Now the right blower has stopped as well. The right blower did enough work to keep me comfortable in the mild winters down here but ..... since I now have zero heat, I figure I will attack the problem now rather than wait until the next winter.

I have a couple of questions ...

When I turn on the ignition key (but do not start the engine) and set the heat to 9 on the auto knob, I can hear noise from the temp sensor in the dash, so far so good. However, I hear nothing from either footwell blowers or the servo in the center. Hmmmm ... I should be hearing blowers running? Servo running?

I checked the fuse in the luggage compartment (#8) .. it is good.

I shot juice to the blowers ... they work with a straight current.

I checked the in-line fuses for both footwell blowers ... both good.

Where should I look next? Am I correct in assuming the blowers will run with the key and heat on?

Additionally, I originally posted in the 911 tech forum. They referred to a rear heater blower. I see no blower on the wiring diagram and do not recall seeing one in the engine compartment? Is there a rear blower on the 87 930?
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Last edited by Shadetree930; 04-22-2009 at 06:28 PM..
Old 04-22-2009, 09:57 AM
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i think they are referring to the na cars which had t.he fan located in the engine compartment. i have been messing around with trial and error on my footwell blowers as well this winter ( thank god i live in so. fla) i think mine is a ground problem in the control unit between the seats, curious to see what the gurus have to say on this thread.
Old 04-22-2009, 10:52 AM
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I have the same sorta problems with my 87 930, I've never got my foot blowers to work. I haven't played with it that much but I'm watching this post to see if I can check mine too. I don't really drive mine in the colder wheather but I'd still like them to work. Good luck.
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Old 04-22-2009, 10:58 AM
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The inline fuses for my footwell blowers were removed when I purchased my car. I replaced the fuses to find that the blowers squealed when they received power. I took them apart and cleaned and lubed them and they worked ok for a few days and started making noise again. I eventually just removed the blowers all together and left the carpeted covers off. The heater output without them is nothing short of amazing although I have lost the ability to route heated air to the windshield. (I suppose I could replumb the heat pipes to correct that)

Any chance pulling them out could work for you?
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Old 04-22-2009, 12:11 PM
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Ok, first off mine is an '84, so may be slightly different than yours. I too had auto heat/cool when I bought the car. Even sorta worked.
My car also has a manual 3 position rotary switch on the dash ,right next to the steering column, on the right. It worked independently from the auto stuff & only turned on the 2 foot well blowers.
All my A/C & auto heat is now removed, so I can not help you track down where the 2 systems are connected, but they were from the factory. So maybe you have a break in that link???

Mark
Old 04-22-2009, 12:42 PM
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Quote:
Originally Posted by Shadetree930 View Post
My problem may be more basic. My servo does not seem to be funtioning. Not really sure where to start chasing down the problem at the moment.

As I have not checked the fuses in the rear compartment, I am hoping its that simple but I now recall hearing some wierd noise coming from the servo area shortly before this problem manifested itself.
You mean the servo that opens the flappers when you turn the dial between the seats? If that isn't moving that may be your issue.

I believe the blowers work in the following way:
Switch between the seats is at 0 the blowers are at rest
Switch at 1-6 the blowers operate at low speed
Switch at 7-8 the blowers switch to medium speed
Switch at 9 the blowers should be on high

They move at the lowest settings to prevent damage to the plastic blower housings from heat. Maybe if your servo isn't actuating the blowers are not ever receiving the signal to turn on?

Do you have the electrical manual for your car? If not I will pull mine out when I get home and see if I can get you any helpful info.
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Old 04-22-2009, 12:45 PM
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I have a question which has been bugging me.....how does the heat get from the heat exchanger to the footwells near the doors? Is it the actual engine fan itself that blows the hot air into the footwells through the flaps in the engine bay which open and shut on command?

Thanks, I am planning on removing the whole heat system and just using the footwell holes so I need to understand this!
Old 04-22-2009, 12:47 PM
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Quote:
Originally Posted by full quack View Post
Ok, first off mine is an '84, so may be slightly different than yours. I too had auto heat/cool when I bought the car. Even sorta worked.
My car also has a manual 3 position rotary switch on the dash ,right next to the steering column, on the right. It worked independently from the auto stuff & only turned on the 2 foot well blowers.
All my A/C & auto heat is now removed, so I can not help you track down where the 2 systems are connected, but they were from the factory. So maybe you have a break in that link???

Mark
I believe the earlier cars are different. In '86 or '87 they went to a system that has the heater controls on a dial between the front seats, it has some sort of automatic thermostat functions but I won't pretend to know how that works. There is no fan switch on the dash of the later cars. (for heat anyway)
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Old 04-22-2009, 12:49 PM
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Hey there Willtel,
My '84 also was equipped with the same "dial-a-temp" control between the seats, it just also has the dash switch, for independent control of the foot well blowers.
The blowers would still come on by using the "dial-a-temp." control, you just also had the manual override switch.
To be truthful, when I bought the car only 1 blower worked. The drivers side had melted into a ball of f&%#*, since Porsche didn't put fuses in line with the blowers till later model years.
Mark
Old 04-22-2009, 01:08 PM
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Go with a early model lever at the handbrake for heat. They never fail.
Old 04-23-2009, 04:22 PM
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When you turn on the autoheat the servo motor makes a funky buzzing noise as it pulls the cables and closes the vents/opens the heat valves in the back.

there's a delay... around 15 seconds later the blower fans come on squealing and blowing lots of very hot air.
..and if oil is dripping on the heat exchangers, smoke too.

It's wonderful on a cold day.
Old 04-24-2009, 07:04 PM
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There is a control module inside the auto heat console. There could be a fault within this module as I am pretty sure that it controls the switching of the footwell blowers. Since you have individually tested the blowers to work and you hear no servo noise. You should hear initial servo noise if the selector is anything other than zero and the ignition key is on with motor not running - I just confirmed this with a trip to the garage. So two things appear to be wrong which IMHO points towards the control module.

As an aside....I first had a heat problem when I got the car....too much heat. The problem ended up being the temp sensor in the dash. There is a small fan behind that small round grill to the right of the steering column that pulls air across a thermister. There was so much dust and debris on this that it was not reading accurately. Cleaned it off with compressed air and good to go.
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Old 04-25-2009, 08:24 AM
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I should have updated my problem scenario ... The servo does work. I replaced the fuse in the engine compartment and after that the servo works fine.

I bought a multi-meter today. I am going to recheck the footwell blowers first by throwing a straight 12 volts to them and making double sure they work. Then I am going to check to see if juice is flowing to the connectors that plug into the fans.
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Old 04-25-2009, 01:30 PM
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Keep up the diagnostics, please. This is the only remaining area in my '87 that does not work, and I've just been too lazy with other more important performance things to worry about it.
I too have the funky dial control between the seats, and can hear the servos running in relation to how far I turn the knob - but I have yet to hear any fan action. All fuses in all fuse/relay panels are good to go, so is there also an in-line fuse stuffed somewhere under the dash? I hope not, 'cause if I start probing around under there who knows what new troubles might surface.
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Old 04-25-2009, 05:49 PM
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There are two inline fuses. One for each footwell blower. Very easy to check, just pull the footwell carpet sections (3 Phillips screws). They are 10 amp blade fuses.

Both replaced in my scenario with no positive impact.
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Old 04-26-2009, 05:45 AM
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For some reason, my footwell fans were running all the time. I finally went in there and pulled out the two red inline blade fuses to get the fans to stop. Are they supposed to run all the time for air circulation....or are they only supposed to run when you activate the heater controls. I believe the AC only circulates thru the dash vents, not the footwell blowers.

Anyone else have theirs running all the time?
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Old 04-26-2009, 02:46 PM
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Quote:
Originally Posted by Chuck Jones View Post
For some reason, my footwell fans were running all the time. I finally went in there and pulled out the two red inline blade fuses to get the fans to stop. Are they supposed to run all the time for air circulation....or are they only supposed to run when you activate the heater controls. I believe the AC only circulates thru the dash vents, not the footwell blowers.

Anyone else have theirs running all the time?
They are supposed to run all the time at low speed if no other setting is calling for a faster speed. It helps to keep the fans from getting cooked.
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Old 04-26-2009, 05:33 PM
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No kidding? I guess I'd better go and put the inline fuses back in there. It seem curious that they'd run like that without first activating the dash levers........but they were running at a very low speed like you said.....I didn't even notice them until recently when one of them was starting to squeak a bit, then I got down there and listened and heard the motors running.
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Old 04-26-2009, 10:25 PM
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Now that you mention it, I do notice (hear) with the engine off and key on...a very soft low fan sound up front. I guess that's the heater fans running in slo-mo. Must be designed to always run for ventilation purposes, I suppose. But are they supposed to ramp-up in response to the thermostat knob setting? If so, I've never been able to hear any change (of course, hard to hear with the car running).
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Old 04-27-2009, 08:55 AM
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Hmmmm.....I think I'll wait to see who else chimes in and verify that these are supposed to run like this all the time....what downside is there to shutting them off if you have no need for ventilation....like say the top is down? Is this some sort of safety procedure to keep air flowing thru the car in the unlikely event of an exhaust leak into the cabin? Maybe another of the US requirements like the smog equipment?
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Old 04-27-2009, 09:04 AM
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