jwillman

The AC system is back in and held a vacuum but now I have HVAC controller issues.

Prevoiusly the fan had operated intermittantly, sometime would work in defrost and sometimes, only on high. I pulled the controller and found a bad trace on the bottom side but could not determine what ir did. I replaced broken slider ***** and reinstalled but no I get no fan at all. When I jump the blower relay pins 30 and 87 the blower works and I am able to vary speed using the fan ****. I tried two other relays and same result with relay installed.

I found the small switch at the back broken, likely happened when I reattached. Looks like it controlls the compressor clutch.

So any ideas? Is it the HVAC controller? Anyone have a controller for sale?

Damit, almost had AC

jwillman

adding pics

blown 87

Greg Brown does a great job on HVAC controllers.
Send him a PM .

He did mine and I m very happy with it.

the flyin' scotsman

Does GB rebuild them Greg?

If so, does the blue relay get replaced? what else?

blown 87

Yes, the relay does get replaced, and there are other things he does I am sure, but can not say what they are.

He does rebuild them and has a full test setup to test every one, it is a 928 cooling system with out the car from what I understand.

Again, send him a PM and ask him.

I like them enough I am going to stock one.

the flyin' scotsman

xcellent Greg.....I'll contact GB directly if I can find his business contact info.

ROG100

On the early HVAC heads there is not much to rebuild and I am not sure Greg rebuilds the vacuum controlled ones. The switch is a simple type and should be easy to replace. Very different to the later heads.

jwillman

I seem to have multple issues with mine. The switch seems to seems to be on off based on teh cam for the lower slider. Seems on when in the AC and Defroster position.

The other issue is the trace on the bottom side and the new issue with the fan only running when jumped.

jwillman

Well I have it fixed - I think

I decided to try some silver conductive paint to repair the trace. Found a pen applicator and filled in the missing area. Once dry it is very hard and I now have comtinuity on that wire and along the trace.

I found a like fit switch to replace the broken compressor switch. The old one was pinned to the controller body so I drilled those out and used bolt and nut arrangement to reattach.

Once reconnected I have control of the fan thru the switch and I get voltage at the freeze switch when in the AC and defrost positions.

Vacuum system still is not right and I seem to have heat all the time which tells me the vaccuum is either not closing the heater valve or it is ***** up.

One question I have is the owners manual states the fan is always on low with the ignition on. Should it only be on low until I move from the off position or will the fan speed be dependant on blower speed **** position?

Right now the blower comes on at the speed set by the switch as soon as I turn on the ignition with the mode selector set to off. I can adjust the blower speed thru all positions with the mode selector in the off position. Is this normal?

Rob Edwards

Yeah, he's got two high-school science fair HVAC head testing rigs, that completely replicate both the early and late systems, different combinations of bulbs light up to indicate each of the slider positions.

Here's the 'later' one, while testing the head unit from my GT:

Alan

Only the fan speed switch on the head unit controls the fan operation sped - except that the HVAC head unit needs to be plugged into the harness to activate the blower relay.

Alan