1992 A/C copmpressor gets no power

[Bmastridge]

So, here is the story. Picked up 1992 corolla with 214k and a bad head gasket for $400.00. Spent $100 getting the head worked, another $100 on gaskets and a new water pump (just because I had it down that far), and it runs like a top. However, the a/c won't come on. Pulled the relay and jumped it on the switch side, and it comes on and blows ice cold. The freon is fine. There is no power to the one wire that goes to the compressor. I have replaced every relay, checked every switch on both sides of the firewall, changed the amplifier, and checked every fuse without out result. The only thing I can't seem to find is the "compressor lockout switch" which supposedly locks out the compressor if it's speed drops below 20% of the engine speed. I don't know if this was a problem before the head gasket repair. Any suggestions would be deeply appreciated.

Thanks

[REN69]

sounds like a wire cut somewhere along the line... trying following the wire to see if there's a cut, if not just rewire it.

[Bmastridge]

If you jump the connections at the relay point the compressor starts. Something is not energizing the relay to allow it to turn on the compressor. I have changed the relay a couple of times. But thanks.

[90 GP]

In addition to the fuse block under the hood and the one by driver kickpanel there is also one near passenger kick panel that has a couple relays and fuses. If I remember it is somewhat behind kick panel. Did you check that one too?

[90 GP]

Here's a link to a wiring diagram for a 90 Corolla ( should be similar) if you want to troubleshoot the circuit:

http://opc.mr2oc.com/online_parts_ca...CorollaFWD.pdf

[Flashmn]

Theres a resettable fuse/relay on the passenger side kick panel, check those out. Then ofcourse the switch itself might be broken...

[90 GP]

I was gonna mention that resettable relay too but on mine when the relay trips the blower goes out at the same time.

[Bmastridge]

The blower still works. This is a much better wiring diagram than in the book.

Thanks

[Bmastridge]

The ECU actually is the last stop before the compressor. There was a trouble code for the distributor (12) saying there was no "Ne" signal to the ECU. Any ideas what a "Ne" signal is?

Again, thanks for your input.

[90 GP]

I think the NE signal originates from the distributor. Might want to trace wiring from distributor to ECM for a break in line.

[Bmastridge]

http://www.corolland.com/corolla/1993-1997/1993.html
This article talks about an "Air conditioning cut" being requested by the ECM* (engine ECU) on the 1993, but says every function was still the same. I tried disconnecting the battery, which reset the other trouble code, but still no luck. I can't find any information on an a/c cut. I am so close to resolving this I can smell it.

[90 GP]

Have you tried checking the pushbutton switch that turns on a/c for continuity? Have you tried using a jumper on the high/low pressure switch? Also have read other posts where there were poor circuit board connections inside computer so you might want to check that as well.

[Bmastridge]

Originally Posted by 90 GP

Have you tried checking the pushbutton switch that turns on a/c for continuity? Have you tried using a jumper on the high/low pressure switch? Also have read other posts where there were poor circuit board connections inside computer so you might want to check that as well.

Your help has been invaluable (especially the wiring diagram) and I am deeply in your debt. Everything in the actual a/c system checks out as far as I can tell. So here is the latest. I unhook the battery for 10-15 min or so. Start it up, and the ac works for about 10-15 seconds before the ECU cuts it off. When I jump the diagnostic connectors (T-E1, I think) the check engine light flashes continuously. That is not one of the code choices in the book. Think the ECU is kaput? Any idea where they hid it? Any idea where the cam speed sensor might be? Thanks in advance.

[90 GP]

IF the check engine light flashes continuously it means no stored codes. The ECU is mounted low on firewall inside car. Can see it if you look up from driver footwell toward middle.( in area of heater footwell vent). I would suspect the low/high pressure switch. Your compressor may have problems internally and is tripping switch. Any chance you have a dual pressure gauge hookup for a/c.? Maybe you could get readings to see if it is in specs in that 15sec run time. Not sure where cam speed sensor is located.

[90 GP]

I found a link on general Toyota cam speed sensor info. According to the wiring diagram it appears the speed sensor is of the type that has unit in speedometer of instrument cluster. It was in TCCS section of wiring diagram 2.

http://www.autoshop101.com/forms/h36.pdf