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  #1  
Old August 9th, 2017, 16:16
AnthonyF AnthonyF is offline
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Got an AC issue, can I pick some1's brain?

I have a 94 XJ and my a/c has always worked and i've had it the past 6 years but i didn't use it over the winter and long into summer until one crazy hot day and boom...no a/c.

The clutch isn't kicking on, the idle steps up and the condensor fan doesn't turn on. It's full of freon and thought it'd be high pressure switch but...nope. Relay isn't getting power (or alteast i can't hear/feel it clicking on, i have tried other relays). I don't have a good set of gauges but im thinking this is more electrical.

I'm drawing a blank. I thought maybe it'd be the HVAC head unit but you can hear the idle raise up but nothing happens.

I did do a search but couldn't find anything similar to my issues and did all I could think of. Please lmk if im missing anything.
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  #2  
Old August 9th, 2017, 16:19
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Green Mesa XJ Green Mesa XJ is offline
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Got an AC issue, can I pick some1's brain?

Have you tested the clutch? While off (engine not running) put power to it and see if it engages.


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  #3  
Old August 9th, 2017, 16:32
AnthonyF AnthonyF is offline
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Re: Got an AC issue, can I pick some1's brain?

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Originally Posted by Green Mesa XJ View Post
Have you tested the clutch? While off (engine not running) put power to it and see if it engages.


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yes, i've sent power to it and it does engage. When the vehicle is running you can def hear the truck struggle. Could it be a clog and too much pressure?
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  #4  
Old August 9th, 2017, 17:05
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Green Mesa XJ Green Mesa XJ is offline
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Got an AC issue, can I pick some1's brain?

Oh it's struggling When the clutch engages. Humm, but it doesn't engage when jeep is running normally.
Gut reaction is that compressor wants to seize. Pressure shouldn't be too high unless freon was added.

Did it try to cool when engaged?

Far as engaging, you tested and the clutch is good, either the electrical isn't good, not providing power, or the drag on the clutch disengages it. Don't know if these jeeps do this, had a modern car we were recharging when my gauges crapped out accidentally put too much freon and the clutch would engage for a second the disengage, lowered the pressure and it found a happy medium. Weird recharge to because we removed the rear ac lines and made it front ac only.

Overcharge would put a drag on the motor too.

I'd probably test if it send power to the clutch when you hit the ac switch in the cab, if that all works then electrical is good and it's a mechanical problem.
I'd also try to turn the compressor clutch by hand when it's off and cool to see how much resistance you get, hard to describe on cars ac I repaired the compressor would feel very difficult to turn but people don't drop by the house to complain about a ac problem until it's to late. A good compressor will have resistance for the pressure, bad compressors usually feels harsher and harder to turn. But I'm not a expert just a jackass with tools.





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  #5  
Old August 9th, 2017, 17:58
Green XJ Jeep Green XJ Jeep is offline
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Re: Got an AC issue, can I pick some1's brain?

Might just be time for a new accumulator drier and a expansion valve
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  #6  
Old August 9th, 2017, 18:35
AnthonyF AnthonyF is offline
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Re: Got an AC issue, can I pick some1's brain?

Quote:
Originally Posted by Green Mesa XJ View Post
Oh it's struggling When the clutch engages. Humm, but it doesn't engage when jeep is running normally.
Gut reaction is that compressor wants to seize. Pressure shouldn't be too high unless freon was added.

Did it try to cool when engaged?

Far as engaging, you tested and the clutch is good, either the electrical isn't good, not providing power, or the drag on the clutch disengages it. Don't know if these jeeps do this, had a modern car we were recharging when my gauges crapped out accidentally put too much freon and the clutch would engage for a second the disengage, lowered the pressure and it found a happy medium. Weird recharge to because we removed the rear ac lines and made it front ac only.

Overcharge would put a drag on the motor too.

I'd probably test if it send power to the clutch when you hit the ac switch in the cab, if that all works then electrical is good and it's a mechanical problem.
I'd also try to turn the compressor clutch by hand when it's off and cool to see how much resistance you get, hard to describe on cars ac I repaired the compressor would feel very difficult to turn but people don't drop by the house to complain about a ac problem until it's to late. A good compressor will have resistance for the pressure, bad compressors usually feels harsher and harder to turn. But I'm not a expert just a jackass with tools.





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I attempted to add freon b/c I thought that was the issue but it did not accept any of it. So I did think maybe it has too much pressure so i relieved a small amount being sure not to go too low where it wouldnt kick on it for that reasoning.

Looking into getting proper gauges since i'd like to know how to operate them.

When I engage the clutch with the vehicle running, it will start to cool but obviously it wont stay on.

I know what you mean about the compressor being tough to turn. I could wrap my head around the compressor if the fan turned on. But it stopped as well.

Thank you for your ideas btw! It's such an odd thing and i bet its something stupid. I checked all fuses too btw.
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  #7  
Old August 9th, 2017, 18:56
JeepNoob JeepNoob is offline
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Re: Got an AC issue, can I pick some1's brain?

Once you get your hands on a proper set of A/C gauges, they're pretty easy to use. Just make sure the internal rod is retracted all the way by turning the knobs (you can watch the rod move up and down while you turn the knob.) and then put them on the high and low side Schrader valves. Putting them on is a bit like attaching an air hose- pull back on the knurled portion, put them over the Scrader valve, release the knurled portion and make sure they're snug. Then you can turn the knobs to the open position and look at your pressures. I like to hang the gauges from the hood when I'm doing this. Try running the A/C (even if it only kicks on for a bit) and look at your pressures. There's lots of charts out there, and almost certainly on the web, for what your high and low side pressures should look like based on ambient temp, whether the system is operating properly or not, what it looks like when X fault is causing a problem, etc.
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  #8  
Old August 10th, 2017, 13:00
elwoodblues elwoodblues is offline
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Re: Got an AC issue, can I pick some1's brain?

No technical help from me, but I got the gauges from Harbor freight for like $45. Just like the ones at autopart stores for more than double. I think it included a chart.
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  #9  
Old August 12th, 2017, 14:47
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Ecomike Ecomike is offline
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Re: Got an AC issue, can I pick some1's brain?

Sounds like it is either clogging, causing a HP spike and a drop in the LP side, setting off the kill switch for power to the clutch.

Or low on refrigerant (then the LP switch cuts power to the clutch). Gauges will tell you which. If the low side drops to zero when the clutch engages, you have a clogged system somewhere. Expansion valve is a choke point for clogging. But other areas can clog too, like the filter drier.
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  #10  
Old August 13th, 2017, 14:53
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Green Mesa XJ Green Mesa XJ is offline
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Got an AC issue, can I pick some1's brain?

Since we are picking brains on ac questions I've got one for our commander.
Beginning of summer I replaced the evaporator in an attempt to find the ac leak. Wasn't the problem so I kept looking, found out the leak was a rear ac line between the body and frame so converted it to front ac only.
New lines (suction & liquid) new dryer, new evaporator and expansion valve,original discharge line, condenser replaced last year.
The problem I have now is the low pressure line wants to freeze when the blower is set for low speeds, at speed 3 &4 it is fine.
The line was vacuumed down for two hours, it was actually vacuumed down twice because a gasket blew at the expansion valve so it was repaired and vacuumed and refilled.
Noticed the low side would drop pressure at slow fan speeds, it was about then the gauges crapped out. Kept adding freon to try to beat the ice and over charged it.
At first I assumed it was the aftermarket evaporator, now I'm not so sure.

Any idea as to cause of the low side ice?




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  #11  
Old August 13th, 2017, 20:55
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Ecomike Ecomike is offline
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Re: Got an AC issue, can I pick some1's brain?

Ice on the outside?

Would be low side pressure too low, too little flow, this a restriction in the expansion valve, I think.
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #12  
Old August 13th, 2017, 21:08
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Green Mesa XJ Green Mesa XJ is offline
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Got an AC issue, can I pick some1's brain?

Quote:
Originally Posted by Ecomike View Post
Ice on the outside?

Would be low side pressure too low, too little flow, this a restriction in the expansion valve, I think.
Thanks Mike.

Yes. I've on the out side of the line, most pronounced at the expansion valve but will ice all the way to the compressor.
Hit the fan to high speed and you can watch it melt. Before my gauges quit they showed the low side pressure dip as the fan speed would slow.
I've been trying to figure out if it's too much humidity in the line for the dryer, the aftermarket evaporator and how the air flows through it, hadn't considered the expansion valve. Though the problem was solved until yesterday when I was driving it, I put the ac to low speed once it gets cool thought To check the line and it was starting to ice. I don't think the fan goes to slow speed much when I'm not driving it so it's probably not much of an issue most of the time.



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  #13  
Old August 13th, 2017, 22:03
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Ecomike Ecomike is offline
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Re: Got an AC issue, can I pick some1's brain?

External freezing is caused by low pressure, There is a low pressure switch that should cycle the compressor off before it can ice up. There is also a temp T-stat at the evaporator, in the dash area that should cycle the clutch before ice could form on the evaporator. So you maybe all three problems, to sensors/switches not working to cycle the clutch off, and a partial restriction.
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #14  
Old August 20th, 2017, 13:55
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Green Mesa XJ Green Mesa XJ is offline
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Re: Got an AC issue, can I pick some1's brain?

Quote:
Originally Posted by Ecomike View Post
External freezing is caused by low pressure, There is a low pressure switch that should cycle the compressor off before it can ice up. There is also a temp T-stat at the evaporator, in the dash area that should cycle the clutch before ice could form on the evaporator. So you maybe all three problems, to sensors/switches not working to cycle the clutch off, and a partial restriction.
thanks Mike. replaced the dryer this morning, vacuumed it down for two hours and it held for 30-40 min.
Recharged and pressures are were they should be for a hot day (93-96 F, high humidity), but I still get ice running on slow fan while driving. Figure the pressure drops as the rpm increases, probably cruse 1200-1500 rpm. At idle the low pressure with slow fan speed is 25 psi, but that drop as the rpm rises.

These newer jeeps have a pressure transducer that should shut off at 16psi low and 450 high.

I can't decide if the expansion valve or transducer is more likely. I'd like to say transducer but I can't get past the nagging feeling the expansion valve could be a problem too since the jeep didn't do this before the evaporator core and expansion valve were replaced.

The only way to test the Transducer is DRBIII scan tool.
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  #15  
Old August 20th, 2017, 19:40
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Re: Got an AC issue, can I pick some1's brain?

Holy Cow!!!

" shut off at 16psi low and 450 high" You sure that is not 350 psi cut off?

I don't like mine going over about 230 psi!!! In 105 F 90% humidity!!! R-134a

Low should not go under 25 psi IIRC. But I never tested mine on cold days, just super hot days.
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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