AC Clutch engagment issue

[memories83]

I am back with yet another electrical issue on my '83 restoration. This time it is the AC. I contemplated not reinstalling any of the AC during the restore; however, I do like creature comforts so I opted to restore the AC system also. The only issue is I cannot get the AC Clutch to kick on. Applying power to the clutch manually with a jumper wire from the battery and it works okay. Therefore I know the compressor/clutch is okay but somewhere there is an electrical problem and no power is getting sent to the clutch.

Here's what I have done so far...
Replaced with all new components:
AC Compressor w/clutch
All AC Lines
Receiver/Drier
Evaporator Core
Expansion Valve
Pressure Switch (inside evap box)
Blower Resistor (on side of evap box)
10A AC fuse in the passenger kick panel
AC Relay (used from donor car)
and fixed all leaks. :ugh:

Did not replace:
Condensor (flushed but did not replace)
EPR valve (scared to crack the seal on this baby)
External Ambient Temp sensor ohm check is okay (.45)

Have not checked:
Solar Sensor on dash
Internal Temp sensor under the console

Vacuumed down system for over an hour and then charged with 1.5 cans of R134 Freon (converted from R12...unfortunately). A few bubbles still exist in the site glass but I think that would be enough freon in it to trip the pressure switch (I think).

The blower works fine and will blow decent cool air plus there is a big temp difference between the suction and pressure AC lines when the clutch is engaged manually.

I have researched this pretty well in the TSRM and on the forum but cannot seem to locate the issue.

Does anyone know of any tests that I can run to test circuitry? Is there another fuse, relay, circuit breaker that I have not found yet? I noticed several test connectors under the passenger dash. Don't know if they are related or not and cannot find any information on it.

Any assistance is well received and appreciated.

Mark

[zuprax85]

so... if u put a 12v wire at the compressor wire wont kick ???? is a new r used compressor? maybe there is not enough freon, maybe your ac switch is bad.

[memories83]

New Compressor. 12v wire to the compressor and it works fine.

I edit the original post to clarify.

[zuprax85]

how do u know u still have freon on the system? do u have gauges on the low and high pressure side?

[memories83]

I am only know that there were no vacuum leaks. Multiple vacuum tests indicated good vacuum for over 24hrs. I know that's not a 100% test but it's all I got. I assumed that 1.5 cans of freon would have tripped the switch. Your thoughts?

[zuprax85]

ok, if u letave the live 12v wire on the compressor, does it get cold inside? what is the air temperature coming out the vents????? in r-134 must be around 40 degrees, if u r not getting that maybe is not enough freon to activate the compressor.

[memories83]

To help answer the freon question I installed my gauges and took the following pics. During both readings the gauges were steady except for slight fluctuations (+/-7 to8 psi) on the low pressure side. I'm not exactly sure what the correct readings should be for an R134 retro system but does this help? Should this amount of pressure trip the clutch switch?

1. Pic of guages while engine uncranked or cranked WITHOUT clutch manually engaged.
http://i174.photobucket.com/albums/w93/memories83/ACGuages_withoutclutchengaged.jpg


2. Pic of guages while engine cranked WITH clutch manually engaged.
http://i174.photobucket.com/albums/w93/memories83/ACGuages_withclutchengaged.jpg

[jukka]

probably not so simple, but, did you remember to connect the compressor's electrical plug - brown plug one wire(on 82's it's off the main harness, 83?)

[zuprax85]

mmm for me its way too low...the capacity is around 24 oz +/- ....

[memories83]

Sorry, I had to leave for the afternoon.

I looked up the AC specs in the TSRM and the LOW side seems high and HIGH side seems very low. Not exactly sure what that means other than the system still isn't charged correctly.

I will try and pump more freon into it tomorrow night and see what happens. Unfortunately I do not have an attachment that I can charge using my gauges so I'll have to do trial and error until I get it up the charge. Anyone with ideas on why the gauge reading is so odd, please chime in.

Thanks!

[memories83]

Below is the excerpt from the TSRM on the proper reading. I've read somewhere here that the R134 is a little different than an R12 but this should be very close...

http://i174.photobucket.com/albums/w93/memories83/AC_004-1.gif

[zuprax85]

could be a bad expansion valve.

[Sean Chung]

It looks like it's not pumping. The low side should be dropping when you engage the clutch. R-134 pressures read higher that R-12 systems. It is possible you have a stuck open expansion valve, and the freon is just circulating without changing states.

[zuprax85]

thats what i see. gauge didnt drop at all.

[memories83]

Thanks for all the advice. That could be why it does not seem to want to take freon... there does not seem to be a lot of suction. Of course, the expansion valve is in worse possible place :). Is there a dfinitive way to test the expansion valve before I tear the evap box back out? Or is the gauge test, THE TEST.

Thanks again...

[zuprax85]

to take the evap is not soo bad, heater is a pita job. i have a new expansion valve for $35 + shipping. (1 year warranty)

[memories83]

I was fooling with headlights tonight so I didn't get around to the AC. Also, I am trying to find a R134 Can Tap to allow me to charge while the gauges are attached. Hopefully tomorrow.

zuprax85... What brand is the exp valve that you have?

[zuprax85]

not sure if is a 4season , ill check them tomorrow.

[Rich64N]

Just an off idea, is the fan running in front of the condenser (the radiator for the AC system)? This is the fan that is forward to the front support brace, in front of the radiator.

[memories83]

Yes, the condenser fan is running. In fact, it almost took a finger off :)

One other thing if it helps, when I engage the AC switch the RPMs do increase. So I would think that and the fact that the condenser fan is running it would rule out the AC switch.

Does anyone know how to override the Pressure switch? Is there a test connector for that?

[memories83]

Had more time to work on the AC tonight and here is what I have.

First: Another one of my duh moments. The gauge readings that I posted earlier were incorrect. I had both valves open, which gave false readings and made everyone think that the Expansion Valve is defective. Sorry! I feel like such a newb.

With my confession out of the way...

I finished charging the system. It would not take freon due to a bad suicide charge hose. It was the type with a trigger (Wal Mart) and it quit working. This made me think the system was full when it really wasn't. So, I bought an old fashioned suicide hose with the screw type can tap and the freon flowed once again. I charged the system completely to the proper pressure (see gauge pic below).

The bottom line:
Clutch will still not engage normally without a hot wire from the battery. Ugh...

One more thing I tried:
I unplugged the wire connector from the pressure switch that hangs outside of the EVAP box and tested as follows.
1. With AC switch in the on position I get 12v power
2. Jump the two connectors with a test wire. The engine rpms increased and the condensor fan came on, however the clutch did not engage.
3. Checked resistance on the pressure switch side of the connector and there was none (0 ohms).

Any additional thoughts?

Here is what the gauges look like now.

AC gauge with compressor clutch engaged manually (hot wire from battery) and engine at 2,000 rpms.
http://i174.photobucket.com/albums/w93/memories83/IMG00053.jpg


For reference, below is the gauge with engine at idle and clutch NOT engaged. Not sure if that tells anything but I thought some of you gurus may want to see it.
http://i174.photobucket.com/albums/w93/memories83/IMG00052.jpg

[memories83]

Okay for the record, I figured it out.

The issue was traced to a short in the Black/White wire from the pressure switch to the compressor. I was very lucky in that the break was just as it was coming out of the wiring harness just behind the battery. I repaired the break and the compressor clutch engaged as it should. Hallelujah! I now have the AC issue resolved!

Thanks to all for their advice and assistance.

On to the next issue...