greaser5

Ohhhh ok... So it's only one wire.

anto1150

Greaser, i'm glad it finally cleared for you. Hope my poor english didn't make too much confusion

memo555

I have the same question.. is the red hot wiring not good enough? Is tapping the purple wire a must?

What's the difference between the 2 methods?

Spyerx

Check my build thread. Maybe 3-4 pages from end you can see method I used. It works fine. I jumped and tapped.

memo555

John McM

I tried both methods on my 1990 C4. First up I tried the 2 relay jumpers. Didn't work. Then I tapped the violet wire as described and I have fan control at all temps. Btw I put insulation tape on the join. It's not easy to solder in there but I feel more comfortable with that than a connector.

sooner964

Ok, so I have a heater bypass installed in my 1991 C2, and, would like to retain heat/defrost capabilities, but have so far not been able to have any success. Maintaining defrost is actually what is more critical to me.

I have tried several different methods to bypass the removal of the heater blower motor. Currently, I have both terminals jumpered, as shown in the picture in Spyerx's post above. Previously, I have also tried the single jumper method (either 30 to 87 or 30c to 87c, I don't quite remember at the moment), as well as Anto's single wire method that jumps the relay to the positive coil. Basically, I think I have tried all of the common jumper methods except for this updated method to tap in to the violet wire associated with the relay. Before attempting this, I'm hoping to pull from the greater knowledge base on RL.

My symptoms - if I first clear out the CCU errors, I can briefly run heat at any fan speed, but within a few minutes, the fans completely cut out. Once this happens, the only way to regain fan control is to turn on my AC compressor and put the temperature **** on full cold (blue dot). If I then move the **** off the blue dot, the fans will immediately cut back out. Additionally, if I hit the defrost button, the fans immediately cut-out. Unless I clear the codes again, I can only run the fans with the temperature **** on full cold.

When I pull the errors from the CCU, I consistently get the following:

Code 15: Rear fan temperature sensor
Code 45: Inside sensor blower motor

I have two questions - (1) is tapping the violets wire (Terminal X as Tore mentioned earlier) any different from Anto's previous solution of pulling +12V from the positive coil, and if so, will this finally solve my problem? Or, (2) is it possible the issue lies with my CCU itself? I am fully willing to tap the wire, but at this point after trying three different methods of bypassing the heater blower motor relay with no luck, I'm starting to wonder if the problem is somewhere else?

Thanks in advance for any and all help. This one really has me frustrated - I've been trying to solve off an on for a year now and almost to the point of just putting the heater blower motor back in. The main reason I took it out to start with was when I did my cat and primary muffler bypass and put in a new O2 sensor, when I went to reinstall the blower motor at the end, I think I had a 993 blower motor from the p/o because it wasn't actually lining up with the bolt studs and was only being held in place by the inlet and outlet tubes. I decided the engine bay looked better without it and got a bypass for the heater blower motor. I really like being able to see more of the engine, and the small amount of weight savings is nice, too.

porsche mania

cant say for any of the other methods but splicing the purple wire works, when I removed the blower I had exactly the same symptoms as you and splicing the purple wire worked straight away. I used a clip to join my wire incase it didn't work so it could be reversed but have had the heat working on my car with no issues for two years and 15k miles. Got to be worth a try as it only takes 5 mins.

sooner964

Thank you, that is definitely encouraging to hear! I will hopefully have some time to try it out tomorrow. I'll report back after I've had a chance to try this solution. Out of curiosity, what awg range seems to be ideal for the tap-in connector?

Thanks again! Fingers crossed!

Streetdaddy

can someone please make a simple pictorial of how to splice these wires( where ,etc)

im no mechanic but would like to try this mod.

John McM

1. Remove heater fan or bypass, depending on what you have.

2 undo three screws holding the rear relay cover on

2. Remove the two forward relays. One is black and one is green.

3. Remove the two 8mm bolts holding those relay holders in.

4. Separate the two holders (they slot together)

5. Look under the most forward relay holder (one that was holding the green relay) for the violet wire. This is the one you want to tap into.

6. Tap into the wire. I used a blade to carefully remove the insulation and then soldered a wire to it. I then put insulation tape around it. You could use a connector.

7. Crimp a spade tab on the other end of the wire.

8, fit the tab into the rear most space in the relay holder that housed the black relay.

7. Test if the fan works on temps between the blue and red dots.

8. Refit the cover etc if it does.

John McM

Pics

Streetdaddy

Thanks John!!

porsche mania

Not sure on the awg range of the connector I used, a friend gave me the smallest one he had. The voltage running through the purple wire is miniscule but still just enough to fool the controller into thinking g the heater blower is still there.

Boesman919

So it looks like the black and red wire is the power the the blower motor. Right now it is connected directly to the blower, bi-passing the switch. The blower motor wire is blue. I was hoping I could disconnect the square connector and then connect the two wires to the switch. I can disconnect the black wire, but the blue wire does not want to pull out of the square connector. I don't want to disconnect the square connector until I'm sure that those are the two wires that have to connect to the switch. I am not sure if the wiring and switch is original 924 parts. I think 944 parts were put into this car.