I'm trying to diagnose some AC troubles, and I'm having one heck of a time trying to decipher the diagrams.

I put together a little diagram of my own:



I little non-standard, I know, but I'm just trying to get this all straight.

http://www.ertyu.org/steven_nikkel/n...000/EPL_8W.pdf is showing an "AC Cycling switch". What is that? Where is it? What does it look like?

Just having a little trouble following the signal path.

I think goes something like this:

1. AC+Blower Switch OR Defroster = ON. PCM AC terminal grounded.
2. Blower grounded.
3. PCM grounds Radiator fan, and AC Compresser Clutch circuits via respective relays.
4. Compressor Clutch circuit is complete only if both High and Low pressure cutoff switches are not open.

Have I got it?

This diagram does not represent accurately how the A/C system works in the Neon..

You need a few special tools to diagnose an A/C system properly, and I wouldn't attempt it without prior experience.

I'm not takin' anything apart, just tryin' to learn how it's put together! Where've I gone wrong?

You got most of it. You were right in saying that when you turn the blower to the A/C or defrost it provides a path to power through the low pressure and high pressure cut off switches then to the PCM. Your Neon does NOT have an A/C cycling switch, that is only in right hand drive Neons.

If the low and high pressure switches are closed then the PCM receives signal voltage. The PCM then grounds the compressor clutch relay which provides power to the compressor clutch.

Also your vehicle does not have an expansion valve but something called a fixed orifice tube.

The best place to start diagnosis is to check the refrigerant level (which requires specialized gauges) and to turn the A/C on and check for power and ground at the compressor.

Don't dismiss this too quickly, though. This actually helps me with my AC problem. I'm not getting power to the "AC" wire in my control switch, but I'm getting power to all my fuses. My compressor works, and the refrigerant is full, but no signal is getting sent to the compressor or radiator fan.

that would be a relay, have you bypassed the rad fan relay yet just to see if ya get 12v?

Ok, I made some changes to the "diagram" (blarg, it's so messy). Did that fix it so that it shows the correct signal path?

Haha yeah man looks good.