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Electrical Problem

homeboymi on Fri November 07, 2014 12:09 AM User is offlineView users profile

Year: 2004
Make: Toyota
Model: Solara
Engine Size: 4
Refrigerant Type: 134a
Country of Origin: United States

I've been trying to fix my ac. I thought at first it was low on freon because the compressor wouldn't come on. I have vacuumed the system and refilled. Now the ac works intermittently with the light on the switch going out and then back on. Sometimes the light stays on and the ac blows cold for days. Yesterday it went out and then back on intermittently. Once it went off and back on while waiting for a traffic light so I don't think bumps in the road is the cause. Right now it is working fine, blowing ice cold air but I never know how long this will last. I have slapped the side of the fuse box under the hood and the compressor came on so I replaced the clutch relay but that didn't make any difference. Slapping the fuse box doesn't work every time though. Is there a switch causing this problem? I'm stumped.

Cussboy on Fri November 07, 2014 7:33 AM User is offline

You need to actually TROUBLESHOOT the cause of the lack of 12 volt positive voltage to the compressor clutch coil. And this needs to be done with the car in the inoperable condition. Get a wiring diagram, start at the AC clutch coil and work your way backwards, find where there is positive voltage if none is at the AC clutch.

If there is voltage at the AC clutch, consider the coil itself, or the AC clutch gap.

homeboymi on Fri November 07, 2014 8:29 AM User is offlineView users profile

Thanks for the reply cussboy. My friend and I were trying to get the compressor to start by jumping the wires at the pressure switch when I removed the fuse box lid. Bingo, the compressor started working! That was when I figured I needed a compressor clutch relay. I could slap the fuse box when the compressor was not working and it would start.. I ordered a new clutch compressor relay but I still had this intermittent problem. Are there any other relays in the ac system or anything else in this fuse box that would cause this problem? Slapping the fuse box doesn't always start the compressor.

mk378 on Fri November 07, 2014 10:00 AM User is offline

Often if the light at the control panel doesn't come on, the problem is right at the control panel. It could be the fan switch if it is old-fashioned manual controls. In any case you'll need to get a schematic and see where the signal is being lost.

Cussboy on Fri November 07, 2014 12:46 PM User is offline

You first need to establish that there is no voltage to the AC compressor when the AC clutch is not engaging. If so, then you can try to troubleshoot an electrical issue.

I've seen broken coils in blower resistor switches cause intermittent operation, "iffy" AC on-off push-in switches, bad connections at pressure switches, silly and wasteful to guess and just throw parts at it.

homeboymi on Fri November 07, 2014 4:31 PM User is offlineView users profile

Thanks cussboy. I know its not the pressure switch because we were trying to jump it and there was no juice until I moved the fuse box lid. I will check the switches in the dash next.

Dougflas on Fri November 07, 2014 5:15 PM User is offline

Why not take the fuse box apart and look for the bad connection? If slapping the box makes it come on at times I would think there is a problem in that area.

mk378 on Fri November 07, 2014 6:12 PM User is offline

+1 See if you can repeatedly make it work / not work by messing with the fuse box. Pull the fuses and relays out and look at the contacts. If there is any evidence of overheating such as melted plastic you'll have to replace the box. Once the spring contacts get hot once they lose their temper and will never make reliable contact again.

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