Greetings - I've poured through the threads on the cup bypass tubes and am ready to put in the jumper wires in place of the heater relay, but I'm not sure what to do with the coiled resistor and the temp sensor which normally reside in the heater pipe.

What did you all do? I've got a late 1991 if that matters.

 

I put them in my RS tube. Just cut out a slot for the coil and drill a hole for the temp sensor big enough for a grommet that will keep the sensor in place:
https://rennlist.com/forums/993-foru...questions.html

 

I have a 1991 as well and I seem to remember reading that the bypass is only recommended for 1992 and newer cars. Perhaps something about a previous CCU version not working with the required electrical mods?

Is there a way to know if your car or CCU is compatible?

 

Thanks for the responses - I'll probably put them into the bypass tube.

I did the jumper wires in place of the heater relay, left the resistor plugged in, and just unplugged the temp sensor and fan plugs, and everything worked great. The cabin fans worked fine on all speeds and no error codes. Also, the resistor did not heat up at all which may mean that it's not getting any juice (will check w/the multimeter tonight).

I believe from the other threads I've read, that I'll need to put a relay in for the jumper wires to avoid battery drain however.

 

I would get rid of the resistor. I recalled the resistor is plugged in line to the blower like this (someone check on this for me) ... +12V controlled by CCU/DME---resitor---motor---ground. When the computer sends the signal to start up the motor (whether you're activating heat or the engine is too hot while parked), 12V is sent onto the line through the resistor to the connector of the motor. For some reason, the resistor happens to fall out of the tube and make contact with any metal part of the engine, it will create a short and possibly start a fire.

The real problem is not that the resistor is still left in place. The real problem is that the resistor still left in place and can flap around and come into contact with metal parts in the car. The resistor itself is just a long EXPOSED wire.