took the programmer board out again. All soldering is solid. This is killing me.

Does anyone know how to test if the signal is being sent from the head unit to the programmer board unit?

When i press the temperature changes on the head unit, the numbers change on the display. i have no reason to suspect the head unit…..but maybe just because the temperature updates on the head unit display that doesn’t necessarily mean the instruction is being sent to the programmer board.

 

contributing some useful info to this longstanding thread for future c4 owners. (have we lost @Cliff Harris )

here are pics side by side of the programmer board with and without the vacuum actuated heatercore flow valve. You will see they are the exact same minus the solenoid and its circuitry. There is another change you cannot see. on the rubber vacuum port manifold….the newer ones…..are plugged where the solenoids plastic nipple would have been inserted on the earlier version.

So, the reason this is important is that many “parts cars” and therefore sources of used programmers, are going to be the older cars. Ive not seen many 87 and later parts cars. 85’s and 84’s didnt have this option. So the 86 is a common junkyard/boneyard year as a source of these and THEY CAN BE USED ON THE 87-89.

I just used my original prammer housing, manifold(whose unused nipplevwas plugged) and the extra solenoid just sits there and does nothing. the blocked rubber manifold port is just bent out of the way a bit.

if you have to use the old prorammer in it’s entirety, id probably just leasve it all hooked up and plug it in. shouldvwork fine. the point is u cant have the rubber manifild unplugged. so keep it plugged into the unused solenoid if you must use the 86 housing…..or i believe you will have a vac leak.

Note, i resoldered the resistors on the replacement 86’s board. Works just fine.

you will see on my og 89, i messed up the thin traces and had to jump the damaged traces with solid core wire. I really dont think that was the cause of the non functional status because i continuity tested it all. i also used a radial vs axial capacitor….which shouldnt have been an issue as long as the polarity is right which it is.

who knows. but its working. and we learned the old boards are forward compatible. If i had an old car, id remove that heatercore valve. they induce premature failure as the heaters are never used and the anti corrosion additives never get replenished in the core.

Simply plug off the vac line and it would be fine. and operate like the later design.

Cheers and Merry Christmas everyone.



later design on bottom

note the bypassed traces

 

Old thread but full of good info, and I had a thought today. If GM got rid of the heater control valve, and the solenoid that runs it, do the later climate control head units still signal it to open and close?
They are generally considered 86-89 compatible parts from what I understand. I came to this thought because my 86 has a 2002 dated reman control head, and I just rebuilt the programmer which
fixed my lower vents never closing issue but the heater control valve I just noticed never closes. The valve works, the vacuum hose is fine.

 

For future reference, a 2002 dated GM reman control head does in fact open and close the solenoid for the heater control valve.
At least when you have a fully functional programmer.