My 1987 5000s climate controls do not work. I bought the car about 3 years ago and it worked for about 6 months, when one day the controls died. Their is no LCD showing up at all, however these climate controls have some kind of backlight bulb in them, and this still goes on when the headlights are turned on. I bought a replacement control, but there was no change. Fuses are good.

 

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Check the connector that plugs into the back, it might be oxidized or one of the pins has fallen out. The new controller did you get if from a salvage yard or new? There are two versions, some early 5000 had analog and the others were digital.

 

Yes, it was the digital version. I got it to work. I traced the wires from the control box back, and i found a red plastic 4-wire connector that had basically been fried. I spliced the wires and reconnected using wire nuts.
So now the controller works, the fan and flaps all move like they should when you adjust the temperature. But now I have another problem. There is little or no heat coming through the vents. No matter how long I leave the car on the air never gets above slightly more than outiside air temp. If I understand correctly the heat comes from the a coolant exhaust hose from the engine. This seems to be hot pretty much all the way to the fan unit. The valve, to open this hose when the heat is turned on, works perfectly. Whats wrong?
I forgot to mention this is the 2.3L non turbo model, with the battery under the back seat.

 

I had a similar problem on my 91 100Q. During the winter sometimes it would blow cold outside air and during the summer the AC would just cut out. After I replaced the flap servo the problem went away. I think that the potentiometer wears out and the controller has no clue what the position is. The other problem spot worth checking is the multi function temperature sensor.