AC not blowing cold (enough)

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SuperTramp

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Los Angeles & Bass Lake
I have a 98 TJ that I think has an issue with the AC. I’ve searched and searched the forum and it can’t find threads on the same issue.

The AC compressor seized up last November and I had it replaced and recharged. It never really got a good summer test until recently.

The AC blows cold when it’s cool-warm outside, but once the weather hits about 85, it can’t keep up and the air coming out of the vents is cool at best.

I took it back to the shop that installed the new compressor and dryer to look at, they checked the refrigerant and said it was full, you couldn’t add anymore. The compressor turns on and off and the aluminum lines are ice cold. I believe the compressor is working correctly. I’ve noticed the air gets a little cooler as I drive down hill and the engine temp comes down a little. Driving uphill it creeps over the 210 mark and the air temp at the vents increases.

Where’s a good place to start in terms of diagnostics?
 
Sounds like the blend door is not blocking off the heat from the heater core when you have selected full cold.

Pull up the FSM under resources for your year and look up the blend door.
 
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I’m trying to learn how to diagnose it myself, I’ve not had great experiences taking the Jeep to shops.

I looked in a little further this weekend. From the drivers footwell I can see the blend door opening and closing. I can’t see how well is seals and I don’t know how well I’ll be able to without tearing it apart. All of the actuators seem newer and working.

A couple things I noticed. When set to dash vents, there is still a decent flow of air going to the feet vent. The door seems to close all the way, but there’s no seal around it.

I believe the AC was added, on the build sheet it notes AC delete. When I had the compressor replaced the pulley had move groves than the belt (both the old and new compressor).

If I look under the glove box there appears to have been a hole cut (probably 3” x 8”) where I can clearly see the fan spinning, does this sound right?
 
Is the blend door vacuum actuated?

If it is, your symptoms are consistent with a vacuum leak or leaky actuator. Going uphill under load, you have lower vacuum. Going downhill, you have higher vacuum. If you floor it, you will have almost no vacuum and can see if it gets hotter.
 
SuperTramp said:
I have a 98 TJ that I think has an issue with the AC. I’ve searched and searched the forum and it can’t find threads on the same issue.

The AC compressor seized up last November and I had it replaced and recharged. It never really got a good summer test until recently.

The AC blows cold when it’s cool-warm outside, but once the weather hits about 85, it can’t keep up and the air coming out of the vents is cool at best.

I took it back to the shop that installed the new compressor and dryer to look at, they checked the refrigerant and said it was full, you couldn’t add anymore. The compressor turns on and off and the aluminum lines are ice cold. I believe the compressor is working correctly. I’ve noticed the air gets a little cooler as I drive down hill and the engine temp comes down a little. Driving uphill it creeps over the 210 mark and the air temp at the vents increases.

Where’s a good place to start in terms of diagnostics?
Click to expand...

A few thinks that need to be checked.
Low refrigerant
Too much oil in system
Blend door not closing completely
Condenser condition ( clogged or too close to radiator)
Fan clutch
 
JKP said:
Is the blend door vacuum actuated?

If it is, your symptoms are consistent with a vacuum leak or leaky actuator. Going uphill under load, you have lower vacuum. Going downhill, you have higher vacuum. If you floor it, you will have almost no vacuum and can see if it gets hotter.
Click to expand...
I don’t think so, it appears to have electric servo motors.
 
SuperTramp said:
I’m trying to learn how to diagnose it myself, I’ve not had great experiences taking the Jeep to shops.

I looked in a little further this weekend. From the drivers footwell I can see the blend door opening and closing. I can’t see how well is seals and I don’t know how well I’ll be able to without tearing it apart. All of the actuators seem newer and working.

A couple things I noticed. When set to dash vents, there is still a decent flow of air going to the feet vent. The door seems to close all the way, but there’s no seal around it.

I believe the AC was added, on the build sheet it notes AC delete. When I had the compressor replaced the pulley had move groves than the belt (both the old and new compressor).

If I look under the glove box there appears to have been a hole cut (probably 3” x 8”) where I can clearly see the fan spinning, does this sound right?
Click to expand...

The doors don’t seal real well, but where the air come out has no relation to temperature. Temperature is regulated by the blend door. A picture of the hole in the air box would be helpful.
 
Easier to hook up a vaccum pump to the connector on the firewall, use the pump to generate vaccum...one...see if it holds pressure and two...see if you can accuate the doors.

Hole doesn't sound normal. Not on my 97.

Sounds like you might be pulling the HVAC box.

-Mac
 
Here’s a couple photos. The hole I was talking about that looks cut in has a flapper, seems to only be open for the dash AC setting, I assume this is air re-circ?

IMG_0249.png


IMG_0247.jpeg


IMG_0245.jpeg
 
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