Twood

Good thinking James944

The temperature sensor is still connected. I will disconnect it see if that makes the difference.

thanks Ken

ThomasC2

An update:

I drove the car yesterday for the first time and with a fully charged battery I had no issues with the fan speed or hesitations. So maybe it was only too little power when I tried this in the garage.

Marc Shaw

I tried this on my 1991 C4 (Feb build) and it worked perfectly.

Marc

Jeff Curtis

I think RollingJack is a Rennlist 964 HERO!!

That was definitely one of the coolest "FIXES" I've seen in awhile!

Twood

I have disconnected the temp sensor but still the battery is going flat. It must be drawing power to somewhere so I will take it to my auto electrician and see if he can find a solution.

Duck

Works great on my 90 C4.

xeps

Interesting...

I still experience the hesitation, but only in one specific scenario; If the fan is turned to 0, and the temperature switch to full hot (red), there is a large delay when the fan is switched on. It lasts anywhere from 4-6 seconds.

With the temperature set to anything else, there is no delay. If the fan is already active and I change to full heat, no delay.

ThomasC2

I'll try that one and see what happens!

Gus

Twood - Did you figure out what yuor short or drain was - I have a 91 Cab and did the 37/80 wire link/ rear blower by pass aslo - front blowers work great but the battery drains over night -
HAve not had time to get into issue yet - Just wondering if you fiured it out - Thanks

Twood

Gus
Because of lack of time I simply removed the jumpers. This stopped my battery drain.
I am wondering if I used the wrong teminals but until I look more closely I will have to suffer no heater but as the southern winter is now here I will have to fix the problem.
Any help will be appreciated because it was so good to have a working CCU.
Ken

Gus

Ken -
Understand all to well - I just have not had the time to look into the issue - But, I know that I have the wiring correct. There are little differences between each year that can present problems - looks like we have found one. I won't be able to check into solution for some time - but will keep you posted if I find anything - Your in a bit of a different situation from myself as we are now going into the summer - so the last thing I need right now is a heater - but blowing cool fresh air is nice also -
Stay in touch
Gus

ThomasC2

I don't have a battery drain. I use a a battery charger all the time when the car is in the garage and it is "sleeping" so this must be a difference between cars or model year.

Twood

Thanks Gus

Any help is appreciated.

Ken

Sire

I have all so a 91 cab with no drain, but do you have a airco? because i don't, and maybe this is the problem.

Twood

Gus and others with a '91 C2

Some back ground - I have the heater bypass mod installed with the resistors in place but could not get the CCU to work other than on the blue (lowest setting)dot. Removing the relay and jumping the approriate contacts made everything work perfectly except that I had a battery drain and after 2 days would find I had a flat battery. So it meant that I had to remove the jumpers and I was back to stage 1.

I went and visited a friend who is an auto electrician last week and rather than confront the problem he went around it.

We installed a relay (See attached photograph) so that power was interrupted when the ignition is off but supplies power when the ignition is on. This has the effect that there is no battery drain when the ignition is off. When the ignition is on the CCU works perfectly-hopefully there will no battery drain over the next few days but so far so good and it has been in for 3 days.