87 C4 Climate Control Head.

[sirfixalot]

I have replaced the face plate on AC control and replaced components as per Battee U - tube clip initially all functions & display worked as per design now buttons operate but the lights above buttons are out & digital display is also out. Bit stumped on this one

[Vettech]

Ummm, on C68  Heater & A/C Control Assembly the book is sparce with details.

But the three (3) panel lamps are powered via connector "D14" and thence instrument lights source. But there is obviously some more cct not shown as these are dimable. 8A-66-0.

The on-board diagnostic mode will not cover panel lights & display.

If pressing the buttons causes a/c to come on/off, fan on/off etc etc then we could assume the on-board Solid State Voltage Regulator is getting 12vdc supply and also giving the required 5vdc output - as this is required to operate the output functions.

The cct diag does indicate that this 5VDC is also sent to the memory cct and I would hazzard a guess and say this also supplies juice for the liquid crystal display.

The only other source is via connector "D4" from the 15A CTSY/CLK Fuse located in the "fuse block". This supply feed should be "HOT at all Times"

At this point I'll revert to technician and say - if you had it open and worked on it, then best retrace your steps, for cracks, dry joints, or broken wires etc. Keep us informed.

[sirfixalot]

The orange D4 connection was the culprit was intermittently going open circuit, retensioned pin in connector and AC head works as designed. I created a fault in the AC valves module when I replaced the 2 x 150 ohm resistors which gives the 5v supply to the blend door motor. I had trouble getting old  resistors out and when I replaced I used 5 watt ones they had moved on board & had broken CB track between the  2 resistors which then gave an intermittent + on the solenoids to operate the air flaps and 5V to blend door.I repaired the track on CB with solder and wire & put a dab of araldite on resistors to stop them moving on board. The clue to the fault was the blend door motor had limited travel unlike the one in Battee video.Every thing seams to be working correctly only thing which doesn't seam correct you would assume when you put on heat to 90 degrees you would assume the solenoid for heater tap would turn on and put vacuum onto tap.It does operate in other modes ok
Does any one have an original tap that can tell me when vacuum is applied to tap is water on or off?

[Vettech]

Well done 99.

And I reckon the only people with the OEM water tap are the converters - since they just love ripping the guts out and throwing them away,  besides dont you want that hot water flowing thru the heater matrix 24/7, ummmm loverly and toasty..

[sirfixalot]

Well I worked out on an 88-89 AC Valve module they deleted the solenoid so looks like thats what does happen