SOLVED: Need help with A/C

TUDrewser · Post by **TUDrewser** » Fri Feb 28, 2014 6:46 am

Ok all, my saga continues with my AC. Everything has been replaced, held really good vacuum overnight, pressure tested system and sprayed soapy water on ever connection, etc. Ran the vacuum pump for about 4 hours before taking it over to Tom's place on Saturday to get charged up with R12. Charge went great, was blowing 46 degrees, and worked great for a few days.

Fast forward to Wednesday, turned on the A/C and nothing. Fan blew fine but clutch wouldn't engage. Pulled the plug off the pressure switch and put a jumper wire in, nothing. Connected the clutch wire on the compressor straight to battery and it engaged and blew cold air. Called Jerry and chatted for a bit but ended with deciding I had to trace wires.

While messing with it, I noticed that I wasn't getting 12v to the hot side of the pressure switch. If I jumped the cold side, the clutch would engage, so wire to the compressor is fine. It looked like the contacts were a little corroded, and I had just washed the engine, so I sprayed some WD40 in the connectors, let it sit, then tried jumping them again. Eureka! It worked! Plugged the connector back into the pressure switch and still worked...blew cold air. Thought it was fixed.

Yesterday went to drive into work for a meeting and no A/C. Jumped the pressure switch, still nothing. If I jumped the cold side of the connector to the battery, it would engage, but jumping the connector itself now does nothing.

Where do I need to check next? Is there a fuse somewhere? Why would it be so sporadic? I am seeing some bubbles in the sight glass, which I though may settle out, so probably need to charge it a little more, but even so jumping the pressure switch connector should engage the clutch. It's driving me crazy...please help.

SJTD · Post by **SJTD** » Fri Feb 28, 2014 7:27 am

Been a looong time since I've had mine running or even seen the AC so I'm not sure but isn't there a temp control on the AC? Maybe it is set to warm or failing. I'd look for power before and after it.

ProTouring442 · Post by **ProTouring442** » Fri Feb 28, 2014 7:46 am

You're going to need a wiring diagram (I think they are available on the "Mother Ship" and check the connections and switches that supply the A/C system with power. You'll also need to check the continuity of the wires themselves, looking for a bad repair or partial break. The system is not very complicated, so you should be able to ascertain the problem fairly quickly.

One thing you can try is turning the A/C on and off very rapidly a couple of times, then leaving it in the on position. if this works, it is likely the switch on the A/C control that needs cleaning/replacing.

TUDrewser · Post by **TUDrewser** » Fri Feb 28, 2014 7:49 am

Thanks guys, gives me some ideas to check. Think I'll pull the control out of the dash and see what the back looks like.

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FSJ Guy · Post by **FSJ Guy** » Fri Feb 28, 2014 8:16 am

Check that controller as well as the thermostat and possibly even the A/C blower motor resistor array. IIRC from another discussion, someone noted that there are fan relays involved, too.

http://oljeep.com has wiring diagrams.

TUDrewser · Post by **TUDrewser** » Fri Feb 28, 2014 8:51 am

Where is the thermostat physically located?

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TUDrewser · Post by **TUDrewser** » Fri Feb 28, 2014 12:38 pm

Ok, looked at the diagram. However, I am fairly basic in my ability to read these. What is the item marked "B5" on here? And the wire that comes out of the pressure switch is light green...what does 160R mean? or 180R mean? Trying to figure out where this wire goes to figure out if I'm getting power.

acdiag.PNG

SJTD · Post by **SJTD** » Fri Feb 28, 2014 1:26 pm

B5 is a connector. Dunno about the numbers. I'd guess they are some metrical wire gauge. On my '84 schematic the wire size is indicated for each wire. Should be a couple pages at the beginning of the schematic that splains that kind of stuff.

Mine has no pressure switch but it is prolly in series with the thermostat.

ProTouring442 · Post by **ProTouring442** » Fri Feb 28, 2014 2:20 pm

16OR should be 16 gauge Orange

18LG should be 18 gauge Light Green

etc, etc

TUDrewser · Post by **TUDrewser** » Fri Feb 28, 2014 2:27 pm

Well, that's kind of what I figured. But the wire going to the pressure switch is light green, and from pressure switch to AC compressor is red, or maybe orange. But the diagram shows wire to the pressure switch should be OR, which doesn't make any sense.

I found the wire in the main harness where it goes into the firewall. At at one point I had continuity between it and an inside green wire that goes to the blower switch, but then I lost continuity. Diagram shows blower switch going to a resistor, so that must be how I lost continuity, but then that wire doesn't coincide with the diagram. There's a Green wire with black tracer coming out of the back of the unit, and it has 12v when AC is on and nothing when it is not, and even has a number 7 on the connector by it (which seems to match the diagram). But then I don't get continuity between that and the green wire in the engine harness, which I believe to be the wire to the pressure switch.

Here's the wiring diagrams:

http://oljeep.com/gw/elec/90_numeric/90 ... age-31.jpg

http://oljeep.com/gw/elec/90_numeric/90 ... age-32.jpg

Getting ready to head out camping for the weekend. Maybe I'll just let my head sit on this and stare at the pages I printed.

jsinajeep · Post by **jsinajeep** » Fri Feb 28, 2014 5:54 pm

You got to remember it a Jeep. You may have an early 90 built in 89 with a 89 wiring harness or a late
90 with a 91 wiring harness and they may of used a different color of wire.

sonoraed · Post by **sonoraed** » Sun Mar 02, 2014 8:34 am

Don't think your wiring diagram is correct,I am installing a 89 GW dash in my 79 J10 and have modified the control head to work with a vintage air gen IV hvac unit
The control head that came with my 89 dashboard has two blower switch's, one for the heater blower (on the firewall with resistor) and one for the ac unit (inside under the dash) the blower switch's get their input signal from the electrical/vacuum switch on top of the control head which is connected to the top mode function lever on the control head,so if you move the lever to ac the ac blower switch is powered up and in heat (heater) blower switch has power
If you look at the diagram there is a ac control module,which acts as a thermostat for the ac system,the module gets a resistance (ohms) signal from the thermistor (in the evap) and the potentiometer connected to the temp lever (control head) if the values are right the module will send a signal to (i think) a relay and on to the low pressure switch then the ac clutch
If any of these components are bad ac clutch will not power up,the only thing that can't be tested is the module,all you need for everything else is a good digital VOM and a decent wiring diagram
The ac controls in my 79 J10 system were simple, a blower switch and mechanical thermostat

TUDrewser · Post by **TUDrewser** » Wed Jun 18, 2014 7:57 am

Ok, here's the update. Finally took it to a shop that was willing to mess with things and troubleshoot. Found two issues:

1) A/C system was empty. Ugh. So I definitely have a leak somewhere. I finally gave in and went with R134 because it's a whole lot cheaper to troubleshoot a leak with R134, especially knowing it's going to leak out, and it honestly feels pretty cold. They could not find the leak right away, so I'm guessing it's around the evaporator fittings inside. Plan is to run it till it's cold, then the dye should show up just fine with the light wherever it is. I'm going to drop the dash down for them to save on some shop time too and give them easier access. They're being very accommodating in that regard.

2) Even with a full charge, the clutch still randomly will not engage. It's hard to reproduce, but turn the system off and on a few times and it seems to eventually reengage. They confirmed my findings that when it's not engaged, there is no power even making it to the pressure switch. So, it's either the control switch in the cab, or they said there is a thermostat switch by the evaporator (which Jerry and I suspected was somewhere...but wiring diagram doesn't show it). The guy said he is positive it has one, and that this switch going out is not only common, but would cause the intermittent clutch issues too. They said they could drop the dash to find it and troubleshoot it, but offered to let me take it home and do that work to get to the switch if I wanted to save on the shop time. Which I did. He even went to his inventory and pulled one out to show me what I was looking for, then told me how to test the switch. Said to bring the switch back to them and they probably have one in stock that will work. Sweet.

So, that's where I stand. Cost me $91 for the troubleshooting and full recharge with dye. Seemed reasonable. And if it seems like I'm reposting this all over, I'm just trying to leave question threads with answers in case someone searches in the future

serehill · Post by **serehill** » Wed Jun 18, 2014 12:47 pm

The thermostat controller knob on the dash that you turn to adjust temperature is the controller that operates the compressor. First though the wire comes from the blower switch to the thermostat. it's also very possible that the blower switch is sending intermittent power to the thermostat. I've seen it both ways. The thermostat controller will have 2 wires coming out of it. one will run to the blower control to get power & the other will go to the pressure switch on the freon line.

looks kind of like this:
http://thumbs3.ebaystatic.com/d/l225/m/ ... z2dt2A.jpg

TUDrewser · Post by **TUDrewser** » Wed Jun 18, 2014 1:15 pm

serehill wrote: looks kind of like this:
http://thumbs3.ebaystatic.com/d/l225/m/ ... z2dt2A.jpg

Yes, that picture is almost exactly like what they showed me at the shop. Where is that part? I assume the coiled wire in the picture goes into the evaporator to measure?

serehill · Post by **serehill** » Wed Jun 18, 2014 1:43 pm

It's in the dash. The knob you adjust the temperature on the A/C control panel.

serehill · Post by **serehill** » Wed Jun 18, 2014 1:48 pm

It's in here you just about have to buy the entire thing.
It doesn't look like the one I showed you but it works the same way
I have never worked on your model I'm sure someone has. I would assume there are wires from this controller tot he thermostat that has the capillary tube That's the copper thingy. follow the wiring from this controller & you'll find it.
http://www.ebay.com/itm/Jeep-Wagoneer-G ... 8e&vxp=mtr

TUDrewser · Post by **TUDrewser** » Wed Jun 18, 2014 2:12 pm

Well just so happens I have an extra one of those to try.

serehill · Post by **serehill** » Wed Jun 18, 2014 2:36 pm

I updated my last post you can replace this controller & try it & if that doesn't work follow the wires to the one with the capillary tube attached. You should be able to follow the wire from this controller to it. I should really shut up since I have never worked on the model you have but it stands to reason the controller makes the piece your looking for work. It could actually be the problem though. It's where the power originates

TUDrewser · Post by **TUDrewser** » Tue Sep 02, 2014 12:52 pm

IT'S ALIVE! A year after starting to work on it, I finally have A/C. It was the damn thermistor. However, it didn't look anything like the one they showed me...it's the copper tube with two wires on the end that goes into the evaporator. I had replaced the evaporator with one Jerry provided because I had a crack in the pipes. However, turns out the one Jerry gave me had a bad thermistor. So, took the thermistor out of my old one and put it on the new one...bingo. Shoved it through the core and put it all back together.

What a major PITA. I had a new control box too but never got around to trying it. Thinking of adding a fan to the condenser since it's now a R-134 system, but I'll see how it does.

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