'90 V8 Quattro heater fan mostly not working

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Tom - 22 Dec 2004 00:56 GMT

The high tomorrow is 5F here in St. Paul and the fan of my heating system
only works intermittantly. It usually runs when I first start the car
totally cold in the morning, but it shuts itself off after about 15 minutes
even though the interior temperature is no where near the set point. After
this, the fan won't come on for the rest of the day, except for very
occasional and too brief moments.

I suspect the car thermostat is stuck open since the water temperature stays
around 60-70C and I know the fan isn't supposed to come on until the water
gets hot. However, the "high" setting on the heater fan is supposed to
override this and the fan does work when the car is first started and very
cold.

Another clue is that the fan worked okay until the outdoor temperature
dropped below 25F as it did recently (and will stay for the next few
months).

I'm going to have the coolant thermostat checked out soon, but I'm not
convinced that this is the problem.

Any suggestions?

Thanks,
Tom

PS: My first car, a 1961 Buick LeSabre, had chronic problems with the
heater. I finally replaced the temperature control with a threaded pipe
water valve in the heater hose and a toggle switch under the dash to control
the fan. Kind of crude, but it was foolproof.

Reply to this Message

Tony - 22 Dec 2004 04:41 GMT

In addition to a thermostat stuck open you have a very common T44 problem.

The brushes in your heater fan are shot.

This is a guess based upon a lot of BTDTs on the four T44s that I have owned and
a number of friend's T44s. I am a regular poster on AudiWorld forum for the
T44 series and this is a question that comes up over and over. The brushes are
ALWAYS the problem.

Fix: Replace the fan motor or have brushes refit at a shop or even DIY with a
set of brushes from your local hardware store.

The real issue as with many projects is getting to the motor. It is under the
plastic shield in front of the windshield (under the hood). The blower is the
big white plastic thing in the middle.

It is about a four hour job and it helps to have help at some points. Stuff
under the dash needs to be removed as well.

Hope you have a heated garage or it can get fairly pricey to have it done. Do
not go to an audi dealer. Their cost will bring tears to you eyes. There are a
few very fair and competent independent shops that can help you if you choose to
go that way.

It is a very irritating problem. I had to deal with that on a drive to Western
Montana from here in Minneapolis. that got cold. One thing I did for temporary
heat was to spray WD40 or CRC on the brushes. that would get them working for
ten minutes or so. The place to spray is on the driver's side of the white thing
that contains the motor there is a black rubber 90 degree elbow. Pull it out and
you will be looking right in at the brushes.

Tony
'91 100q 5spd
former T44s '87q 2:'84FWD

> The high tomorrow is 5F here in St. Paul and the fan of my heating system
> only works intermittantly. It usually runs when I first start the car
[quoted text clipped - 25 lines]
> water valve in the heater hose and a toggle switch under the dash to control
> the fan. Kind of crude, but it was foolproof.

Reply to this Message

Tom - 05 Jan 2005 04:51 GMT

Tony, you are absolutely right. I took the car into the shop and the fan
motor needs to be replaced. You were also right about the time. Their
estimate is 4 hours. Lots of bucks for a fan, but I don't have the
wherewithal to do it myself and Minnesota is too cold to go without a heater
fan.

Thanks,
Tom

> In addition to a thermostat stuck open you have a very common T44 problem.
>
[quoted text clipped - 60 lines]
>> water valve in the heater hose and a toggle switch under the dash to
>> control the fan. Kind of crude, but it was foolproof.

Reply to this Message

Tony - 05 Jan 2005 17:45 GMT

If you are in Minnesota (I am too - Excelsior) a friend of mine has an
Audi shop in Wayzata. He is very good and has very fair prices.

Email me if you want his number.

Remove 'nospam' in email address to contact me.

Tony

> Tony, you are absolutely right. I took the car into the shop and the fan
> motor needs to be replaced. You were also right about the time. Their
[quoted text clipped - 69 lines]
>>>water valve in the heater hose and a toggle switch under the dash to
>>>control the fan. Kind of crude, but it was foolproof.

Reply to this Message

Audi3.6 - 23 Jul 2009 23:47 GMT

I also have a 90 V8 quattro. The fan works but the heat control i
unregulated. It's trying to find the median range but it either cycle
too cold and then too hot. I believe it may be the sensor by fan in th
dash that draws in cabin air past the sensor. I replced the instrumen
cluster bulbs and had to remove the dash. I believe I may have disturbe
the sensor that controls the regulation of the electronic module. Anyon
have other ideas

--
Audi3.

Reply to this Message

TonyJ - 24 Jul 2009 16:59 GMT

The type 44 series has a more common failure that can cause this. The
vacuum lines that control the heater flaps may be broken or the vacuum
motors that actuate the flaps may be failing. These are located under
the dash on the center heater vent box. It could also be due to the
heater control module that is located under the dash on the passengers
side an can be reached by removing the glove box. It has vacuum lines
and a cable running to it. The cable operates the heater flap in front
of the fire wall just in back of the blower fan.

Another common issue to check is the outside air recirc flap which is
also reached on the fire wall right next to the controller (behind the
glove box). This has two typical failures. The vacuum lines break / fall
off the vacuum motor that operates the flap and the return spring breaks
and needs replacement or its plastic mounts fail and need to be fixes by
improvising a fix.

The heater control unit in the dash is rarely the problem.

> I also have a 90 V8 quattro. The fan works but the heat control is
> unregulated. It's trying to find the median range but it either cycles
[quoted text clipped - 3 lines]
> the sensor that controls the regulation of the electronic module. Anyone
> have other ideas?

Reply to this Message