xcoldricex

I read that the rs heat bypass doesn't really affect fan output. however when I installed mine I am getting very low fan output and turning the fan **** from 1-4 doesn't do anything. is this because I need to hook up the unplugged lines that went to the elbow that was replaced or do I have broken fans in the dash?

Vandit

If you set the CCU to max cold or max heat, do the fans work properly?

Vegas993

You removed the rear blower motor, so yes, it does affect fan output. You need to remove a relay from the fuse box in the engine compartment and make jumper so you can control the fan speed of the secondary blower in the dash. The type of jumper depends on the year of the car.

https://rennlist.com/forums/964-foru...uestion-2.html

DobermanDad

When I did mine, the heat still blows. A little less, but I still get heat.

Did you do the relay mod?

xcoldricex

works now! removed the heater blower relay and did the mod as detailed in

https://rennlist.com/forums/964-foru...-solution.html

thanks DobermanDad. i have a 1990 and the wire was purple just for another data point

I don't really notice a difference in fan power without the heater blower fwiw.

DobermanDad

Mine was the same color as described in the DIY. 89 C4.

I also didn't notice much of a difference in fan power.

David A

You can get a dummy relay.

https://rennlist.com/forums/993-foru...pass-tube.html

xcoldricex

yeah I was wondering if that would work - I may do that to make it even easier to reverse

DobermanDad

That mod only works with newer 964s. 91 and up.

Vandit

My car is a mid-year '91 (plastic intake, circular latch) and I don't run a rear blower, I don't have any special jumper arrangement, and my interior fans operate like normal when my CCU is set to max cold.

My understanding is that the interior fans works like normal even w/o the rear blower as long as the CCU temp **** is set to Max Cold or Max Heat. Set it anywhere in the middle, and the CCU shuts them down because of the lack of the rear blower.

xcoldricex

mine only worked on max cold, not max heat without doing the wiring modification.

DobermanDad

Mine too.

FlyinTomato

I just ordered that bridge adapter. Will report back if it works. I have a 92