So from a service manual I'd downloaded I've been going through AC troubleshooting steps.
A couple things are pointing to the AC diode, for the life of me I can't find the bugger!
Seemingly it's above the inside fusebox/left side kick panel, but there's remnants of an old security system and some added wiring. The loom is loose and I've looked all around but to no avail, as well as behind the glovebox where it looked like someone had found it after a Google search.
Guess I'll skip it for now and go on to the next step, compressor clutch,

 

Radiator fan relay is good, both fans kick on via shorting the plugs, as well the clutch clicks jumping but I didn't actually test the condenser and clutch relays. Rad fan control gets current across Yel/Whi which points at check wire to AC diode. The AC thermostat seems good other than I get no V across Blu/Yel & ground, which points at check wire to pressure switch.
So I'm guessing it's likely that it may be one or the other of the components instead of the wire. Still not sure about the diode location exactly and the pressure switch looks to be under the battery, but may be reachable from underneath...

 

I'd start testing at the pressure switch. I put my negative volt meter on good ground (- battery terminal or a valve cover bolt). One wire to the pressure switch should have 12V to your good ground, and the other wire should have near zero resistance to ground (or use the continuity setting).

Once you figure out what is missing, we can provide the next step(s) for testing.

 

Ok, so with the car up on ramps I crawled under, with the key in the on position II.
Across the terminals of the switch I got continuity.
Both wires on the plug had V and limited continuity, about 11.6V, and on my digital multimeter continuity dropped from 1 to .863 for one, and .868 for the other.

Also, related or not, not sure, speed 4 doesn't work on fan switch.

Just came across this Google'ing:
I jumped blu/yel to ground, started the car and nothing.
Going to look around a little more and go and test ac and blower switches.

I did just recheck the t'stat according to the manual, check for V across blu/yel and blk/yel. With the connector unplugged, I get V across blk/yel but nada on blu/yel.
Does it make sense that I get V across blu/yel at pressure switch but not t'stat?

 

Your first test is confusing me. What did you use for your volt meter ground? What units are you getting for your continuity? I'm also not sure how you are getting 12V on both wires at the pressure switch.

You can measure continuity between two points by measuring resistance. An open circuit would be the same reading on the volt meter as having the meter leads touch nothing. A closed circuit would give the same (or close) reading as touching the meter leads together. The units are ohms or milliohms. Let us know the units.

There is another setting on some volt meters that beeps when the circuit is closed and doesn't beep when the circuit is open. The symbol on the meter looks like the symbol for a diode on an electrical drawing.

 

I had the neg probe on the neg battery terminal for ground.
Yes, I read somewhere while doing an LED project that the continuity function is essentially measuring resistance. My el cheap meter doesn't beep, but starts at 1, if I touch the probes together it drops to 0. Continuity to ground from the pressure switch plug, both leads dropped to .865ish average.
Being you said one PS lead should have 12V and the other near zero resistance, I tested to ground and continuity on both. I'm going to guess the reading is ohms, my meter gives no indication other than it starts at 1., the period is a decimal which is displayed until any resistance is measured at which point it drops to triple digits, .000.

 

Well, anyway, the service manual I downloaded points to two things, checking the AC diode and repair open in blu/yel between AC t'stat and pressure switch.
So I guess I need to hunt some more for the diode and try and trace blu/yel.
Thanks anyway.

 

Sorry about not replying. The 1. reading on your meter sounds like it is infinite resistance. The number you get when you get a real number should be on the dial you set for resistance, or lcd of the meter.

If speed 4 is not working on the blower, make sure the fan speed is set to a speed that works the fan blower.

At the thermostat, what resistance/continuity reading do you get between the blu/red wire and ground?

Just to be thorough, unplug the pressure switch, and jump the switch with a piece of wire or a thin paper clip. What happens?

The diode is way above the fuse box on the driver's side of the vehicle. I never looked for mine on my old 95 accord, but I read where it is closer to the top of the dash. You'll have to look for a green and a red/wht wire going to it. Sorry I can't provide more information on the location.

 

Have you checked the ac thermostat? Location is behind the glove box. I had a similar issue earlier this year. Culprit was the ac thermostat. Will see if I can find a picture.

 

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