I hate to ask some basic questions, but did you have the battery hooked up when you did the voltage test? Was the key in the II position?

If you reinstalled the battery, you may be able to reach that plug from underneath the car.

 

Yes I had the battery in at the time. But I didnt have the key in, I just reread the manual and it did say the key had to be in the #2, I feel so stupid.. And I tried to get to it from under and I couldnt. Even if I would have jacked it up its still too cramped.

 

Im gonna take a flashlight out and check it again if I can get to the switch

 

OK, I was able to barely get the plug off from the top by carefully rearranging some of the AC tubes, and restested the red/ white and it did have 12volts. So Im at a loss here. Any more ideas?

 

There is one last test you should try.

What you want to do is unplug the temperature sensor A. This sensor is bolted on the thermostat housing and has a green connector. The two wire colors going to that connector are green and black. What you want to do is short that connector using a piece of wire or a thin paperclip. Turn the key to the II position. If both fans should turn on, then you shorted it properly.

Turn off the ignition switch. Check to see if the red/wht wire at the pressure switch is open or closed to ground.

 

Hey I did exactly what you said. I removed the connector from the t stat "A" (with green and black wire). Shorted the green and black together, then turned on ignition to II position and only the right fan came on. I tried it several times and when I removed the jumper the fan stopped, put it back and still only the right fan. Just in case I was shorting B instead of A, I tried the other one too and it did the exact same thing, except for that one the right fan ran in a different key position. So I thought maybe I had left something unhooked or popped a fuse or something when I was working on it earlier so I put the connectors back and turned the car on, with AC and both fans ran.

Even though only one fan was running while the connector was shorted I decided to check the red/ white to ground anyway just in case I was overlooking something. And with the "A" connector shorted between the green and black the red and white had no continuity to ground. This was with the ignition off as you said.

 

All I can say Is I have been working on Hondas a long time and I have never experienced your problem A/C clutch coming on with out turning on A/C. The diode has me very curious. Its a one way electrical flow only. That may be your answer. Good luck . Find out how to test a diode. I honestly Dont know of the top of my head. maybe continuity one way but not the other. but how do you check that. maybe see if voltage will travel one way but not the other. IF it works both ways somethings not right. You see, the ECU doesnt recognize that your A/C compressor is engauging therfore it does not send an idle up signal.

 

You check a diode w/ resistance measurement function of VOM. In one direction, the resistance should be very low (almost a short), and in other direction it will be very high (open circuit). A bad diode may show a low resistance in both directions or open in both directions.

good luck

 

That last test I suggested was to test the diode without having to find it. That diode is somewhere above the driver's side fuse box. It sounds like the diode is working properly. You could try unplugging the diode to see if your problem goes away.

With the tests done so far, this seems like it is an ECU problem, where the ECU is grounding the compressor relay when it shoudn't. There is always the wiring that could be crossed too.

There is one more test that should be done try to eliminate the wiring.

Jump that temperature sensor A on the thermostat housing and unplug the compressor clutch relay. That compressor clutch relay is on the shroud of the condenser fan (driver's side fan) close to where you add washer fluid. There are two relays there. The relay you want to unplug has 4 wires going to it. The colors are blk/yel, wht, red/blu, and red. Start the car. The blk/yel and wht wire should have 12V. The red wire should have 0V. The red/blu wire should be open to ground.

TexasHonda, you probably have the same 94 manual with the wiring diagram I am looking at. Do you have any suggestions?

 

You need to be more precise in your terms. "Switch" could be AC Switch on AC panel, AC Pressure Switch, or Blower Fan switch. Not clear which. The AC pressure switch should be shorted (pressure in acceptable range)and must be for compressor to engage.

I can see how the compressor could engage w/ AC Switch OFF. It would require a failed-closed AC switch or I/O wires shorted at the AC switch. These wires are Blu/Red and Grn in my manual. However heater blower fan would have to be in an On(1-2-3-4) position for this to happen. Suggest your turn Blower Fan switch to OFF and see if compressor ever engages. If not, this points to a bad AC Switch.

From your description, I think the circuit is behaving as expected. Compressor is commanded by ECU grounding compressor clutch relay; why? Because ECU sees voltage on Red/Wht fall from 12V to 0 when ground is completed through AC Pressure Switch, AC thermostat, AC Switch, and Blower Fan switch.

Both radiator and condensor fans should come on w/ AC compressor. If not, a bad fan or bad fan relay.

Another possibility is short of Blu/Red wire to the AC Switch to ground. This would allow compressor to engage, no matter the position of AC Switch or Blower Fan Switch.

good luck