A/C issues ??

I realize this is kind of a bad time of year to care about the A/C in my truck, but I do know that the defroster uses part of the A/C system to clear things up, right?

So, heres the deal. Early last summer I was using the A/C when a trendil of smoke came up out of the climate control panel. I shut the truck down and tore into the dash to find (and put out) the fire. Luckily there wasn't much going on, but the A/C quit working. After an afternoon of digging into the dash a little futher, I found that the fan control switch had fried and cooked part of the wiring harness. I bought a new switch, picked up the harness pigtail from a salvage yard, along with another climate control panel (mine was broken and was loose in the dash).

Now the fan works again, the heat works great, but the A/C compressor won't come to life. I have hot-wired the compressor directly and it still functions perfectly, but it's not getting juice. I have checked all the fuses and the splicing of the wires I did on the harness. The pushbutton switch in the climate control panel seems to be fine also. What am I missing?

I can live without the A/C this winter (Iowa is good for keeping the inside of the truck cool), but I would really like to have it back for the summer months, plus I know the defroster will work better if the compressor will work. Any ideas folks?

Thanks in advance...

Dave in Iowa

My crystal ball is cloudy- can't see the year and body style of your truck-

A good wiring diagram will explain- perhaps you got a wiring harness for a non-a/c truck-- I'll look it up when the crystal ball clears up...

My bad... it's '98 Z71 5.7 litre Silverado
The truck the wiring was removed from had the exact same control panel. I got the plug and about 10" of wiring. When the switch fried it cooked the plug end, so I spliced on a new one. Pulled the parts myself, so I know I got the right parts. Wondering if maybe the actual A/C pushbutton switch is bad in the new control panel.

I assume the brown wire going in to the control head has power since the blower works--so does the Lt Green wire at terminal C3 have +12v when you push the a/c switch? if not- then switch is bad-- you can actually measure this easier at the HPCO switch on the rear of the compressor- underhood without opening up your dash- confirm an inop switch by jumping 12v directly to dark green/wht wire- this should bypass the switch and tell the PCM to turn on the compressor--

Was the a/c cooling good prior to control head snafu? There is a chance the a/c is inop anyway due to loss of refrigerant- if so you can jumper the cycling switch connector on the accumulator- to see if compressor engages. Is your compressor belly oily/greasy? This is very common on OEM compressors.

I've already bypassed the switch by applying power to the green/white wire on the compressor. It comes to life just fine and the A/C works. The A/C worked perfectly before the meltdown. Its just since I replaced the panel that it doesn't seem to be getting power. The only thing I can think of is that the switch is bad in the replacement panel.

No oil or nastiness on the outside/underside of the compressor.

I was afraid you'd say that-- You did not read carefully- there are two plug-ins on the compressor- the one you jumped into-- and the one on the rear of the compressor- sort of hidden-(a high pressure cut-off switch)- unplug it and see if there is 12 volts there- on the light green wire-- this comes directly out of your control head- if no 12v signal there- then yes you have a problem upstream- like at the control head out-- (check it there as well now) and /or in the a/c switch .. I was just trying to make it simple for you- so you did not have to pull the control head back out of the dash right away....