climate control testing

[mytrplseven]

Is there any way to verify. sans a wiring diagram, that the a/c switch is working? '86 944. I've installed a newer climate control and new a/c relay. The relay doesn't seem to be getting energized.

[kdjones2000]

Do your fans go on high speed with the switch?

[djnolan]

I printed out pages 208-210 of vol 4. This is the 87 diagram and is slightly more detailed than the 86 version. First note I think the snowflake switch is mislabled as the evap icing protection.

I traced the A/C lines with a higlighter starting at the AC terminal on the coolant fan switch and ending at the compressor. It goes through the snowflake switch, TCU pin AB, ac relay, low pressure switch and ends at the compressor.

The pin 6 of the 6 pin connector should have 12v coming from the TCU to trigger relay.

It looks to me if you remove the cooling fan relay and apply 12v to the ac pin the compressor should engage if everything is working and the snowflake switch is on. Only do this for a few seconds as the cooling fans won't be running.

It is a real complicated circuit. If pin AB of the TCU isn't energizing it could be one of the temp sensors or the TCU itself, or a loose connection.

[mytrplseven]

Where is the 6 pin connector? In the diagram the symbol for the ice protection switch appears the same as the low pressure switch...different from an actual electric switch. Your observation makes sense, though and I've run through that circuit many times and it still didn't make sense as depicted.

[mytrplseven]

Yes, KD. The fans work properly and the light in the switch capsule comes on when depressed.

[djnolan]

I think the 6-pin connector is part of the climate control module if memory serves me correct. Do you have your old one you could post a picture of?

There is definitely some missing information in the diagram and a picture of the climate control module would help fill in the gaps. Another thing I notice is the sliders, the dfrost switch and the recirc switch are also missing in the diagram unless they are the three rectangles with the arrow at 2 oclock.

[mytrplseven]

The only connector that even comes close, and has only 5 pins is this one on the back of the climate controller. Is it the one you're referring to?

[djnolan]

Looks like the connector to the blower resistors from the pin numbers (c1, c2, etc). It may be along the cowling based on the icing switch location.

I found a TCU schematic on Renslist. It's all there except the snowflake switch, maybe the diagram got cut off to the right where there are 2 lines ending.


Original post here: https://rennlist.com/forums/924-931-944-951-968-forum/879940-heater-control-panel-repair-with-schematics-2.html

[kdjones2000]

Read pages 87-60 thru 87-64 on your shop manual for troubleshooting the A/C and climate control head.

[mytrplseven]

I don't have shop manuals

[djnolan]

The ones I have were available on the web for free. However, I am not sure if they are considered legal to download. Maybe someone else can confirm this.