Porsche964FP

Here is my problem (I'm quoting a gentlemen who had the same exact problem):

"Now I have a problem in that the fan speed control seems to only activate the blower if the temp setting is to full cold. Any movement towards warmer temps causes the fan to shut down."

"In addition the defrost will only blow for about 2-3 seconds and then needs to have the button released and pushed back in before it will work again...for 2-3 seconds."

"Interestingly if the fan speed control has activated the cabin blower when the defrost cuts out the cabin blower also stops and won't blow again until the defrost button is released."

"If I do these actions with the engine off so I can hear servo activity I can hear servo actuation. I think this is weird because the defrost button should not be controlling any servo, only the defrost blower. I should also point out the the 2-3 second time of the defrost blower working and the similar time required to reset it seems coincident with the sound of the servo actuation."

The garage has told me it's the rear blower that needs to be completely replaced (£500 + labour), however could it just be the resister within (as per this gentlemen's past response):


"You most likely have a rear fan resistor problem, and the CCU is shutting it down as a failure mode. Check the fan resistor that is in the rear blower tube. Those can fail too. Its a springy thing that is inserted into the rear blower tube on the Left side of the engine bay... it runs from the heater box connection up past the distributor/coils and up to the rear blower fan."

Some help would be much appreciated.
Thanks

Computamedic

This is the classic symptom of the rear blower failing to run. The REASON for the failure might need some investigation though. It can often be something simple such as a blown fuse (it was uprated by Porsche to a 30 amp part early in the 964s production), but often a blown fuse hides the real reason - such as a seized blower motor or worn bearings etc.

The ballast resistor merely is used to control the speed - resistor in-circuit means slow speed, resistor out of circuit means high speed. When defrost is selected I would expect the rear blower to run at high speed - and that would eliminate the ballast resistor as a problem.

The blower relay can also be source of problems. You can swap the one from the oil cooler (in the front fuse box) to check it. They are the sane relay type.

You should be able to hear the rear blower running if the engine isn't started.

Hope that helps.

Regards

Dave

Porsche964FP

Hi Dave thanks for the help... turns out the rear blower motor is completely shot, bearings gone etc, etc, etc so it'll have to be a new one! just wish they weren't £500!

thanks

evoderby

Hi Frank,

There's a more economical alternative to buying a replacement blower whilst adding a bit of RennSport in the process :-)

The RS rear blower delete tube (149GBP ebay.co.uk) gets rid of the rear blower, which saves about 3,5 Kg in weight and greatly increases engine bay accessibility. Only thing needed in addition to get your heating system working again is to short the rear blower relay socket.

I am in Amsterdam with the same crappy weather as in London, the heating works perfectly on my 964 with the above described mods.

Computamedic

Frank,

There is an even cheaper way to solve the problem - you can buy just the rear blower motor from Bert Gear at Berlyn Services (web site here) - part no. BOS0130.111.145 at a cost of £128.08 (inc VAT). Sorted!!!

Regards

Dave

Porsche964FP

haha that sounds fantastic... thanks for all the help guys... Rennlist is such a great place!

Porsche964FP

Mind you/ having said that if i replace the whole unit, i know i won't have to face any other troubles with it. New fan, relays etc, etc... should be a good investment!

And besides Iv'e managed to squeeze 15% off the £500 price tag for a whole new unit!

And i do want that rear blower! thanks for the suggestion though, evoderby!

Thanks again guys

Crystal Cranks

Rear Blower on E Bay Here

Even with shipping would be much cheaper

Porsche964FP

Thanks! Although the problems all solved"

BlackBear

How did you seperate the motor from the fan?

Did you heat it up?

crg53

The fan is PLASTIC, you can use a 3 prong puller to remove it and when you install it on the new motor, stand the motor on end so the shaft is sitting on something solid, then tap the fan on using a piece of wood and a hammer. Spin it to make sure it is running true and adjust if needed.

PS. Before you remove the fan from the old motor, make some reference measurements, that way you can install it in the same place on the new motor.

BlackBear

Thank you.

The motor will be here tomorrow. I just have to go buy a puller.

I bought the part below for $142.95 at http://www.usautoparts.net, hope its the right one.

Part #: W0133-1602886
1989 - 1998
Porsche 911 Bosch Blower Motor Blower Motor 911

mrmandmman

Thought I would revive this thread because my car was having the same symptoms (front fans work with temp all the way cold, defrost works for a few seconds then stops, heat stops the front fans from working, although heat does trickle out). I never hear the rear blower running.

I swapped the oil cooler relay. That didn't help anything. I pulled the rear blower and hooked it directly up to 12V. It works fine, I had it replaced with a rebuilt one a few years ago.

Pulled codes prior to doing anything and got these:

24 - Fresh air flap motor
41 - Condenser blower motor
44 - Rear blower motor speed 2

I cleared them and then tried to turn the heat on again. It didn't work and I got this new code:

45 - Inside sensor blower motor

EDIT: Maybe solved - I pulled the wrong fuse the first time (it should be the top one in the rear fuse box right next to the heater tube). It was burned. I would think that a blown fuse is typically not a cause but perhaps because it was a 25 year old 25A fuse and I believe 30A fuses were used later that it could be the fix itself. Could be that the inrush current when that motor starts is right at 25A or something. We'll see if it happens again.

rod635

Hi hope someone can help, My rear blower is not working. I removed the blower connected it to a car battery and it worked. Next checked the power lead, no power, checked the fuse ok, removed & checked the relay, that was ok too. Checked the fuse and relay contacts and it there is no power going to fuse or relay.

Any idea what is causing this?

1990 C4 Targa

R

ToreB

Have you turned up the CCU temperature setting to start the fan?
Is the CCU working at all? servos moving? main blower fans work when you adjust fan speed?
Here's a HVAC test procedure: https://www.bergvillfx.com/categorie...test-procedure
Cheers,
Tore