heater fan

[Dkennel]

Hi,

here is another question:

when I start my heater fan (with the red center levers) I initially hear a loud screechin, squealing sound. I can almost adjust the sound with the levers, and after a minute or two it disappears.
Is my fan motor(s) going bad? Where do they sit? sound seems to come from the front, but I thought motors are in back?
I saw on a German Porsche board somebody talking about lubricating the motor??? Would you use motor oil? Silicone?

You guys always have great advice and experience. I appreciate this board and the host very much. Looking forward to responses.

Later,

Dietmar

[1982911SCTarga]

One wonders if the Apollo program influenced the Porsche engineers who developed the 911's HVAC system -- as in "we need more blower motors!"

Anyway, the heater blower motor lives in a demanding environment and is being constantly baked in the engine compartment. Mine started squealing last weekend on a run through the Shenandoah. I unplugged it (you still have heat when the car's moving). When I got home, I took it apart and the motor was very stiff to turn. I sprayed the front bearing with some Kroil and let it dry, then lubed it with a few drops of 3-in-1 oil. Runs nice and quiet again (for now).

If you have to replace your motor, look for the thread on here about the Grainger replacement motor. Save money that can be put to use into good stuff.

Brian

[Dkennel]

sorry, but what is Kroil?
where are these motors located? I have a Bentley manual and will dig in there to look also...

[1982911SCTarga]

Kroil is a penetrating solvent.

I "think" your 911 has a heater blower in the engine compartment and footwell blowers in the passenger compartment. What a nice upgrade. More blowers!

You'll need to listen and locate where the squealing is coming from to figure out which blower is acting up.

A good trivia question would be how many electric motors are on any year 911. Quite a few if you include all the blowers, power windows, antenna, etc.

[der Mond]

The blower motor is immediately to the left of the air intake tube for the fuel injection that sits on the top middle of the engine. There is a shroud/tube that runs from the lower left of the engine compartment up to the fan, which is the black circular item up on the upper left atop the engine. The motor is behind the fan. Mine did the same and when I removed it, it became clear that the bearings were shot. There have been many attempts by many owners to replace the motor with an inexpensive replacement, but I have not heard of one yet which has not resulted in the footwell auxiliary footwell blowers being disabled, because they are on the same circuit (the footwells will only run once the main blower is "on") and the resistance in the main blower is apparently unique to that motor. If posts from guys who have pulled it off successfully follow, then make up your own mind how to go. The ones I have seen have required complex-sounding Jerry-rigs and I just decided to bite the bullet and purchase Pelican's replacement. My front central fresh air blower started making noise about the same time, so I ended up using the Bentley manual the best I could to remove that assembly (behind the carpet in the luggage compartment under the dash) and I replaced the motor insert in that also. All in all it was an expensive summer but I guess that's the cost of a 18 year-old car if you want plain old peace of mind. I have to say that with every job accomplished I bond with the car more and get more hopelessly addicted. One more comment - I have heard many folks bash the Carrera heat/vent system up the wazoo, but after a year and a half of ownership and finally getting the hang of every possible combination available in varying weather conditions, I now feel that Porsche did a fairly good job given the air-cooled limitations. I'll duck now before the cream pie - OUCH - too late...

[JBO]

Speaking of the heater fan, when I pull up on the red levers I don't hear anything, though I do get heat (but not a blast of heat). I guess this means my engine compartment blower is out? If so no big deal, as I was thinking of pulling it out anyway. If I pull it out, I know from the archives that I can cap the left side, but what about the right side that has the long house that goes over the engine? Anything that can be done for "free" ( i.e. not buying the fiberglass blockoff plates)?

[911Atlanta]

Dietmar -- how did a German like you end up in Lubbock Texas ?

Anyway, welcome to the 911 Board. I've got an '87 also and am in process of swapping out / fixing all my blowers -- expensive indeed. der Mond (French guy ?!) is right on regarding the main heater blower -- it's in back.

However, based on my experience, if the squealing you're hearing sounds like it's coming from the dash area, it's one of the footwell blowers. I had the exact same sound -- high pitched squealing that stops after a bit -- and it was one of the footwell blowers. Pretty easy replacement -- they're located behind the curved carpeted panels at the outside of each footwell. They each have an in-line fuse also ( a fuse placed in the wiring harness), so make sure to check that on both. One of my blower fuses kept blowing and I determined it was the badly-worn blower -- when they're in bad condition they'll blow fuses quickly.

Also, while you're fixing up your heating system, make sure to check, clean and replace fuses in the engine compartment. Believe it or not, there's a separate fuse/relay panel on far the left side of the engine compartment, behind a curved plastic panel held on by two wing nuts. the silver square boxes are relays -- one controls the entire heating system, but if you get juice when you pull up the red levers, it's ok. $250 relay, so good that you get sound when you pull them. There should be three regular fuses in there also, one of which also is for the heating system -- I swapped all of them out for new ones while I was in there.

* One way to check to see if it's a footwell blower or the main blower in the engine compartment: pull out the in-line fuse or disconnect the wiring harness from the likely footwell blower then turn on the heat -- no squeal equals that's your culprit. If it still squeals, plug that one back in and do same on other side.

Hope above helps !

Dan

[Walt Fricke]

Dietmar is lucky in that he not only has the footwell blowers, but they have in-line fuses. The '84s had the blowers but not the fuses. The electrical parts of the motor themselves (specifically the brush holders) served as the fuse, but not without first letting off a bunch of acrid smoke, guaranteed to scare the wits out of car owners not mechanically inclined. The footwell blowers (take the upholstery pieces off - held with a coupld of screws - to inspect them and their fuses) are, if anything, an even cheaper piece of work than the other blowers, though you'd not guess this from their price. As bearings wear the plastic fan part starts rubbing on its housing. This causes a greater current draw, which can melt the brush holders (or, if fused, blow the fuse). I have heard of the fan friction welding itself to the housing also. Nothing rebuildable short of being possessed of some machining tools and a fierce determination to bring a poor piece of equipment up to Porsche quality at an exhorbitant expense in time and effort (neither of which do I possess).

If my experience with one '84 is any guide, you can expect these fans (footwell and engine mounted) to fail within roughly a year of each other, so if one goes the other may not be far behind. The engine mounted fan is of somewhat better quality, but I have had little success in oiling it.

It doesn't make a whole lot of sense to me that the dial heater controls (with or without the automatic heater system) would care about the resistance of the engine mounted blower, but maybe it does. I have never seen an actual schematic for the PCB that controls the heat (the usual fix when the automatic heat control system fails is to replace the PCB if the sensors and other parts are working properly). That would be a shame, as electric motors can be designed to run without maintenance for a very long time and using such motors on a 911 would be very nice.

Walt Fricke