barneys964

I have a 90C4 in which the blower final stage control unit needs to be replaced. I searched in the thread to see if there was any posts on how to replace. If anyone has information, I sure would appreciate it.

Rocket Rob

Just to be clear, are you referring to the control unit that manages the two fans inside the front trunk? They boost the air flow into the passenger compartment. If yes, that unit is easily accessed. The control unit is bolted to the removable firewall between the gas tank and the heater/air conditioning unit plenum at the base of the windshield.

Just curious, why do you need to replace this unit? In general these are very reliable. You almost never see any mention of them having problems on Rennlist.

Procedure is outlined in the factory manual. I will try to recap it from memory.

• Open the trunk :-)
• Disconnect the battery (negative terminal)
• Remove the water shield
• Remove the fuse panel cover
• Remove the two allen bolt holding the fuse box (note: don't drop the bolts)
• Remove the bolt on the left-hand side of the vertical panel
• Disconnect the wiring connector at the center of the vertical panel.
• Slide up the vertical panel. I had to alternate lifting each side.

At this point, you have the mini-firewall out of the car and you will see the control unit bolted to the center of the panel.

I hope this helps and good luck on the repair.

barneys964

I had 3 problems-
-The fan speed control blew fuse #1 past 1/2 way
-The fan would continue to run after ignition was turned off
-current draw on battery to drain it.
It was isolated to the blower final stage control unit. New part is $481. dcauto has a used one for $95 w/exchange warranty.
Thanks for the information. I feel I can do this.

barneys964

I just want to thank Rob for his assistance in this project. My son and I replaced the part per the instructions and everything went well plus saving alot of money.
Thanks again

easttorks964cab

Barney

hi, this is interesting as i think mine has failed too. i get blow into the cab but it is constant and is not affected by turning the fan control swith on the dash, sound familiar to you?
once youd replaced yours did you get a good variance in blower speed?

hope you can help

chris

barneys964

I had 3 problems - 1) #1 fuse would blew when fan speed was higher than 2. 2)fan would run after ignition was turned off and 3) draining the battery.
I had the dealershipship trouble shoot the problem and it was with the control unit. It took my son and I about 1/2 hour to replace. I got the control unit from dcauto in Atlanta. Everything is functioning normal and Rob's directions were good.

jperret

Let me add my experience. I had a battery leak of about 1 amp, which nearly drained the battery in one night. Checked here and sure enough when I pulled fuse #1 the battery drain stopped.
Shopped for a blower final stage at Porsche Salvage Yards and got a great price ($125) for the guys at LA Dismantlers. I live nearby so picked up the part. They through in some minor hardware parts I need as well.
The installation was very a bit easier than Rocket Rob suggested:
# Disconnect the battery (negative terminal)
# Remove the water shield
# Remove the fuse panel cover
# Remove the two bolts holding the blower final stage
# Disconnect the wiring connector at the center of the vertical panel on the blower final stage.
# Slide up the vertical panel. - poped right out.

Total time to take the old one out and the new one in about 20 min
Tools needed 6mm socket 8mm socket + 8 mm wrench +13 mm wrench (battery terminal)

You guys rock - thanks for the posts, they saved me a lot of time.