Heater bypass - definitive wiring solution
#61
Instructor
#62
Rennlist Member
Yes this is how my 91 is done! Works great. Ya I had to use one of those crappy blue wire tap things :-(
#63
Rennlist Member
Just tried this wiring bypass, but the relay control wire feeds into fuse 14 and that fuse blew. The result was no air conditioning on a hot, muggy day. We confirmed it's wired correctly. Any idea why fuse 14 is blowing?
Thanks,
Wired the bypass correctly but lost air conditioning with blown fuse 14
Fuse 14 (serves rear fog light and reverse lights)
Thanks,
Wired the bypass correctly but lost air conditioning with blown fuse 14
Fuse 14 (serves rear fog light and reverse lights)
Last edited by Foxman; 07-12-2017 at 09:00 PM.
#64
Did the blower delete on MY 90 C4 Cab, with A/C. Used the bypass relay, 964-610-184-00, and can confirm that my front fans are working. I also have the violet wire but didn't use this. My mixing servos were non functional but I am part way thru refurbishing them and have heat. Even with the rear blower done and only one frunk flapper open, there is plenty of heat from the stock heat exchangers.
#65
Rennlist Member
Did the blower delete on MY 90 C4 Cab, with A/C. Used the bypass relay, 964-610-184-00, and can confirm that my front fans are working. I also have the violet wire but didn't use this. My mixing servos were non functional but I am part way thru refurbishing them and have heat. Even with the rear blower done and only one frunk flapper open, there is plenty of heat from the stock heat exchangers.
I'll give the relay a try. If if anyone else can chime in as to why the fuse may be blowing with the wire method, I'd greatly appreciate it.
#66
Instructor
My car is a 1990 UK C2 manual without air con option.
I have intermittent fan on any heat setting except cold. On cold it works consistently. I can't seem to resolve it. Currently I'm running a switched live from the coil, and have previously tried the cross jumper with the same result.
I looked at doing the mod as per the OP, but my car does not have the violet wire. As per other posts I started looking at the yellow/green, however I have 2 of them one thick, one thin. They both go to the '9 oclock' position where my switched coil jumper plugs in. I'm completely stumped now! Using a meter, there does not seem to be another switched live under there to try. Anyone have a solution?
I have intermittent fan on any heat setting except cold. On cold it works consistently. I can't seem to resolve it. Currently I'm running a switched live from the coil, and have previously tried the cross jumper with the same result.
I looked at doing the mod as per the OP, but my car does not have the violet wire. As per other posts I started looking at the yellow/green, however I have 2 of them one thick, one thin. They both go to the '9 oclock' position where my switched coil jumper plugs in. I'm completely stumped now! Using a meter, there does not seem to be another switched live under there to try. Anyone have a solution?
#67
Three Wheelin'
Hi guys ,
I am taking the opportunity this thread is back as I am quite confused, and my wiring does not make the fans working well at all temperature ...
My car is manufacture in 1992 and I have the AC.
I did the first type wiring suggest by Anto, with the wire going from the + coil to where the relay is with a 5 amp fuse, quite tidy as I manage to have the fuse inside the box,
but the fans only work when the temperature setting is on cold, or sometimes not and sometimes suddenly work ... so its not really working properly,
would anyone had succefully done a wiring on a 92 car with AC, what would be the best way of wiring ? a picture would be great ,
Thank you !
I am taking the opportunity this thread is back as I am quite confused, and my wiring does not make the fans working well at all temperature ...
My car is manufacture in 1992 and I have the AC.
I did the first type wiring suggest by Anto, with the wire going from the + coil to where the relay is with a 5 amp fuse, quite tidy as I manage to have the fuse inside the box,
but the fans only work when the temperature setting is on cold, or sometimes not and sometimes suddenly work ... so its not really working properly,
would anyone had succefully done a wiring on a 92 car with AC, what would be the best way of wiring ? a picture would be great ,
Thank you !
#68
Hey, I'm working on removing the blower. I put in the bridge adapter, disconnected the blower and the fans still work, so that's good. I am wondering what to do with the resistor and temperature sensor that sit in the tube. How can these be disconnected? I've poked around a bit but cannot see where the wires go. The car is '90 C4.
Thanks for any help,
Tore
Thanks for any help,
Tore
#69
Three Wheelin'
Just bumping this old thread. Going to try the factory bypass relay on my MY 90 car and wondering if there is also a fuse to be removed (as shown on the 993 fuse box) for our 964s or if just the relay worked for folks?
#70
I’d leave the relay... simply remove the blower, swap the “blower motor” resistor with a simple jumper, and then replace the NTC sensor with a 10k ohm resistor.This will allow the CCU to think everything is normal temp (no need for fan on cool down), but fools it into thinking it’s working those other times (call for heat on start up).
#72
Hi all,
I have a 964 C4 and tried all a.m. wirings without success.
The purple cable solution was my last hope, but I didn't succeed.
Whenever I raise the temp from the blue point the fwd cabin blower shut down
Has anybody an idea?
Cheers,
Matthias
I have a 964 C4 and tried all a.m. wirings without success.
The purple cable solution was my last hope, but I didn't succeed.
Whenever I raise the temp from the blue point the fwd cabin blower shut down
Has anybody an idea?
Cheers,
Matthias
#73
Instructor
In reality, I've gone back to using the rear blower motor, as I like to have working heat when needed, especially when I need to demist/defrost the front windscreen in the rare times it is both cold and humid in Houston. My "butt-dyno" can't tell the difference between with and without the rear blower motor, but my feet can when its cold
Last edited by sooner964; 08-08-2022 at 12:08 PM.
#74
hi, thanks for your reply, mine is build in 1989 MY90, with A/C option hence with purple cable.
as soon as the heater flaps open, means temp in cabin is less than the selected one on the temp ****,
the cabin fan shut off.
Maybe you are right and I will re-install the blower again, but somehow it must work, as many of us made it...
as soon as the heater flaps open, means temp in cabin is less than the selected one on the temp ****,
the cabin fan shut off.
Maybe you are right and I will re-install the blower again, but somehow it must work, as many of us made it...
#75
Burning Brakes
Just thought I’d provide an update on this as I completed the blower removal yesterday.
My 964 is a C4 MY90 with build date of October 1989.
Its a non AC car so I was able to jumper between the two relay connectors to provide a switched +12v to fool the HVAC CCU.
Its basically the violet wire mod without putting a cheap splice connector on.
Dash fans work perfectly on all heat and speed settings.
Hope this helps some of you.
Violet switched +12v jumper.
Genuine Porsche RS bypass pipe.
My 964 is a C4 MY90 with build date of October 1989.
Its a non AC car so I was able to jumper between the two relay connectors to provide a switched +12v to fool the HVAC CCU.
Its basically the violet wire mod without putting a cheap splice connector on.
Dash fans work perfectly on all heat and speed settings.
Hope this helps some of you.
Violet switched +12v jumper.
Genuine Porsche RS bypass pipe.