ago 85 carrera

I have searched the forums and found plenty on fresh air blower motor troubleshooting but my car's problem still throws me. I've owned the car for a couple years and the problem seems to be getting worse.

The car's an 85 with standard controls for the fresh air/defogger blower (three sliders on the dash control head and 1-2-3/Defrost mode on the switch between the seats).

I don't think the blower is at fault like so many past threads point to so I did not dive into dismantling things. Here's why:

The blower turns on when the switch between the seats is turned to 3/Defrost. No screeching bearings, no protest, no blown fuses.

The blower will not turn on when the fresh air dash slider is pushed to the right (hasn't worked since I bought the car). The fan symbol on the dash control lights up but I don't know if that is a guarantee that the fan is getting power.

In addition to the blower not working at all through the dash switch, operation through the 3/Defrost switch is now intermittent. It stays on when it turns on, but it sometimes doesn't turn on. The car is a fair-weather car so I don't use the 3/Defrost switch that much but it seems to be less predictable than ever before.

Any thoughts on where I should start looking?

Thanks.

der Mond

If your '85 is at all like my '87 then the dash switch controls the actual "fresh air blower" - the one mounted inside duct work in the front luggage compartment near the dash. You should be able to hear that blowing through the dash if it's working. Do you have levers between the seats as well? Moving a lever upwards actuates the heater blower that sits atop the engine and blows warm air up from the heat exchangers. When you move the round switch betwen the seats, it should actuate the auxiliary blowers located in your kick panels on either side. They will only go on if the rear blower is actuated by moving up a lever. If your car is different, please excuse the confusion. And study the owner's manual if you have one. The heating/fresh air system on the 911 is initially confusing, but it eventually makes sense if you study it and experiment.

theiceman

Der Mond

Do you remember where the thread is that I went through and explained about the two blowers and how they work .. have lost track now . I think Jeremy may know as he has it all figured out now.

ago .. do more search ,bottom line there are two blowers, you are hearing the hot air blower in the engine , not the fresh air blower in the dash..

der Mond

Guys,
When I was troubleshooting my heater blower (I ended up installing both a new blower in the engine compartment and a new fan motor/blower insert in the fresh air duct) someone passed this article on to me and I hope it will help y'all.
Dennis

http://www.porschenet.com/bruns02.html

ago 85 carrera

Thanks for the great info. It's amazing how much is written about the HVAC system on these cars.

I took the fresh air blower out today and pieces fell out of the motor (the brushes I think). Replacement seems as straightforward as removal.

For Bentley manual users, removal takes less than an hour but if you go by Section 850 (Fresh Air Blower, Removing and Installing), don't go the whole nine yards. I realized part-way through that the Bentley describes removal of the entire system and not just the fan/motor housing. You don't need to remove the intake grill and the bolts behind it nor do you have to disconnect the T-duct from the trunk floor. Simply disconnect the electrical harness, the cable controls, and the two hoses to the fan/motor housing. The housing comes off the rest of the system after removing the two 8mm bolts.

der Mond

Another initiation into the mysteries of the 911! I also had to translate from the Bentley Manual when I did the job, but as you have, I found it do-able. The foam butterfly valves in the ducts were pretty fragile on mine, but I just soaked them with silicone and re-installed. Don't be surprised if your main heater blower motor goes next, if it hasn't already been replaced. They are non-rebuildable. Many guys have found cheap solutions to an OEM motor, and most of them have found out that afterwards the kickwell blowers stop working. There must be something mystical about the resistance in the OEM main blower motor. Once it is switched on, the subsequently live circuit to the kickwell blowers just isn't "right" unless the juice goes through an OEM blower motor first. Unless someone follows this post with a workable solution. There are many threads at PelicanParts and here regarding replacement blower motors. At least that one's pretty easy to replace. One more caveat - at one point my rear blower motor refused to shut off despite the levers being all the way down and the key out of the ignition. Culprit was the main heater blower relay, a rectangular silver one that plugs into the engine compartment relay/fuse block, which is under a black plastic cover mounted to the inside of the left rear fender just aft of the coil. A large butterly nut should secure it at the top. Those relays are more than a C-note and only available from dealers. A great discounting Porsche parts man is Kenn Young at Hennessey Porsche in Atlanta. I doubt you'd find a lower dealer price than Kenn will give, and they ship anywhere.

[kyoung@hennessyporsche.com]

Good Luck!
Dennis

theiceman

where does the footwell blower reside ? wonder if I could upgrade my 78 ..hmmm...

Dan Cobb

If you have 'map pockets' along the lower portion of the front wheelwell (just ahead of the actual door opening), ten you would have to do a ton of swapping, not to mention getting the air to the blowers fromt he rear of the car.
I went through this entire circuit last year and replaced the rear motor with an affordable aftermarket part. I also had to do a little extra wiring to make the footwell blowers function as expected due to the reduced current draw from the brushless motor.

My guess as to why Porsche did it this way is that if the footwell blowers turn on independantly from, but at the same time as the back blower motor, you couldn't tell if the rear motor was functional.
By it controlling the operation of the front blowers, you now have an indicator of bad things. if they don't work.

The fresh air blower and ducting is on my list to 'enhance' this coming year.
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theiceman

Sounds like more of a pain thn it's worth. I do indeed have MAP pockets .. thanks for that .. didn't know they were there till you mentioned it .. just thought it was carpet.

My heat is just so weak thought I could spruce it up but i guess not without a ton of work.

der Mond

Thanks, Dan, you then would be the man for 'ago 85 carrera' to contact if he wanted to go that route. I think what you said about the auxillary blower arrangement allowing an additional way to know if the heater blower was out makes sense. Well, have we exhausted this one?

Dan Cobb

I'm not certain that they are actually "Map Pockets"; that's what i was told once, but it is strange to see that a fifth of your favorite elixer fits right into them like a glove.

I wonder if this is how the German engineers initially expected you to keep warm?
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