Air Conditioning

I've had my 97 Cherokee in the shop (many moons ago, when it was still under warranty) to have the AC checked. They gave me that "operating to spec" line, and I accepted it. This is after replacing the high pressure switch that was causing the AC to go from acceptably cool to nothing, because everything had frozen, and after running the 'vent' setting for a little bit and thawing it out, back to 'ok-cool'. Since then, it never gets to 'ok cool'. It takes forever to get the cabin to a decent temp when it's above 80.

Since then, I've had a 00 TJ who's AC was MUCH colder.

I don't think I have a leak, because the performance of the XJ's system hasn't really deteriorated.

The compressor runs in 4-5 second on to 4-5 second off cycles. This seems pretty rapid. What does that tell me?

How much should I expect to pay for a charge, and will it be worth it?

Is this just a crappy system or should I have hope?

If the compressor cycles more than 5 times in one minute at high speed/max cold then the coolant it low. 97+ XJ's and ZJ both had cheap assed evaporators in the heater box and they leak. Cost is $680 or thereabouts to fix, 8 hours labor as the entire dash has to come out. I need to have mine done soon with summer coming.

I'm going to try the charging route first. If it gets cold after that, and by the end of summer (or the week) and it back to 'kinda cool', I'll get that fixed.

I'm good for replacing things that aren't broken yet. My entire cooling system is new except for the heater core, most of it 'just because'. AC work is out of my league, though.

How much does the charge run, $$ wise?

You can pick up a kit for about $15 with a hose, adapter and can of R134A. All you do is put the adapter end on the can, screw the toggle handle till it pierces the can lid and connect to the low pressure feed on the line between the compressor and tower on the firewall, the connector itself is on the aluminum line right by the power distribution center. Just snap it on like an air hose to an air tool, turn the ac on high/max, back the toggle out of the can and turn it upside down, will probably empty the can in about 15 seconds. You will know it's going in because the can will start to sweat. Thats all there is too it.
Now that said, if there is air in the system from a leak it may not take ANY or very little R134a in which case the system needs to be evacuated [all freon removed] and a vacum drawn for about 20 minutes, this will remove all air and moisture in the system. Then it can be recharged. If you do recharge it use the R134 with the dye in it, then you can look for bright yellow stains with a black light. Whatever you do don't put any R134 with sealer in it, it ticks off the ac shop and can contaminate their stock when they recover it.

I'm not doing *anything*. A SHOP is gonna do it.



I'm sceeered.

TacticalFats said:

I'm not doing *anything*. A SHOP is gonna do it.



I'm sceeered.

Click to expand...

Two minute job for $15 or around $150 at a shop. I'm cheap....

If you haven't already done so, you may want to have the compressor clutch check on yours.

After replacing my high pressure switch, it wasn't too much longer that my compressor clutch went out. Had the same symptoms you are experiencing now. The clutch is a dealer only item as I couldn't find one anywhere else on the open market. Parts and labor came out to $480 for me. But it's been working just fine ever since.

If you question the condition of your entire AC compressor, then replacing it all might be better. That of course being if you find out you are having problems with the compressor clutch.

Ivan

Just last night I finally decided to try something to fix the issue I was having where my 97 A/C would never come out fully cold. I was always curious because the temperature knob never seemed to go all the way to the cold side, it felt like it was hitting something prematurely and not going all the way over like it did on the hot side...

I was pulling the radio to remove my CD changer cord and while I was in there I took off the A/C control panel to look behind it just to see if something was hanging up. What I found is that the knob is mounted to a shaft that turns a small pinion and the pinion sits inside a partial sun gear (a gear with the teeth on the inside of the outer edge) and that gear pushed/pulled a cable that (I assume) moves a damper for hot/cold air.

Sure enough, when going to hot, the gears "bottomed out" and when going to cold, there was still a few teeth left on the sun gear that it couldn't use because it hit an internal stop in the knob.

The sun gear is held on a shaft with a simple little spring-loaded latch that I used my key to release, I popped off the sun gear and rotated it around a few teeth and put it back on.

VOILA! REAL A/C!

I'd suggest anyone with the "not real cold" A/C problem take a look at this first. It takes all of 10 minutes (remove the switch panel below the A/C controls to look at the back side of the switch, gives you more room to work because of the cable attached to the temp knob.) and only involves pulling off the trim around the radio/A/C and 7 screws.

TacticalFats said:

I'm not doing *anything*. A SHOP is gonna do it. I'm sceeered.

Click to expand...

Nothing to be scared of; this is one of the easiest jobs you can do yourself. Unscrew the cap on the low pressure (the big fat one) line, attach can, set A/C to maximum with the engine running, and let the can go until it won't take any more. Seriously, there's no sense paying a shop to do something that simple.

On a related note: does anyone know what the correct low-side pressure level is? I need to do mine this weekend and would like to be able to get a baseline for where it is now before I start topping it up.

casm said:

On a related note: does anyone know what the correct low-side pressure level is? I need to do mine this weekend and would like to be able to get a baseline for where it is now before I start topping it up.

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With Freon, temperature tells you the same thing as pressure just different numbers. Tape a thermometer to the suction line, run and record the temp and convert it to pressure with a standard Freon chart.

However, neither will really tell you how much Freon is in the system. If it did, why did they use sight-glasses on AC? The way I qualify if a system is low on charge is to block-off about 1/2 the air-flow across the condensor coil with cardboard or something. If the suction temperature/pressure drops significantly in a few moments while operating under this reduced "capacity" it could probably use a little charge. If it doesn't change much, I'm afraid that's all you're gonna get, assuming the system is not having other problems.

Learn how it really works. It's not hard and it's "cool" in more ways than one.

XJXJ said:

With Freon, temperature tells you the same thing as pressure just different numbers. Tape a thermometer to the suction line, run and record the temp and convert it to pressure with a standard Freon chart.

Click to expand...

That's cool (no pun intended), but I don't plan on buying a thermometer this weekend. There's a bunch of maintenance stuff I need to do and the $20 or so I'll spend at Rat Shack on it would be better spent on gear oil and LSD additive.

However, neither will really tell you how much Freon is in the system. If it did, why did they use sight-glasses on AC?

Click to expand...

Hence why I was asking for baseline low-side pressures. Not being an ass here, but as informative as your answer was it didn't really answer my original question.