A/C Stops working after about 30 min

[pmacaula]

'97 Explorer XLT 4x4 (6cyl SOHC) - bought new & have had good experience with it for the most part, but the A/C stopped working at the end of last summer.

During service a month ago, the local dealer replaced the accumulator & recharged the system (what they diagnosed as the right fix) just before a family vacation involving long drives.

A/C worked fine for the first 30-45min of each day's drive, then air flow slowed right down & almost no cold air, even if I cranked up the fan.

Have checked a few other threads & don't see anyone with quite the same problem, but the most similar situations have some recommending a replacement of the orifice tube (may have been clogged by debris/gunk ?).

Any thoughts on solving this ? Family is a bit tired of running 60/4 A/C on long drives this summer.

Cheers. Patrick.

 

[Evil Eye]

I would think you are low on R-134a and it's causing the compressor to freeze up after 30 minutes.

 

[pmacaula]

Shawn - could be, though the problem occurred the day after the dealer fixed it and apparently recharged any fluids
in the systems. What is the role of R-134a ? Is it the refrigerant ?

I took her back to the shop today & they did not seem to be able to figure out the problem, though did not charge me.

They suspect the problem is a dirty/clogged Orifice tube causing the system to freeze up during extended use.
- they apparently were worried about replacing the tube because another part was apparently seized & there was a risk that they could damage the core of the evaporator during the replacement, costing mucho $.

Anyhow, I left with the suggestion that I turn off the A/C any time it stops working and trying it again after 20-30 min, after the system has time to warm up and 'unfreeze'. Not exactly ideal when driving around for work in a shirt & tie...

Any thoughts on on how to diagnose ?

Cheers. Patrick.

 

[Evil Eye]

Another part apparently seized? There's only one mechanical part in the AC system and that is the compressor. Not sure what else could seize... At any rate, they would have to evacuate your refrigerant (R-134a), pull and replace your orifice tube, and recharge. Sounds like they either didn't want to do the job or didn't know what was wrong.

PS. I'm just offering up suggestions, but there are others on this forum that are a lot smarter than me that can hopefully offer more advice.

 

[fodowvovo]

could be the a/c pressure switch not causing the compressor to switch on.

 

[zonianbrat]

I agree with Evil Eye. If they did in fact say seized then that would be the compressor (as far as I know) I dont know exactly how the ac system works but again like Evil Eye said it sounds to me like they do not know what they are doing. I would take it to another dependable shop and get their opinion.

 

[jpacetti]

It could be after the dealer charged the system that it bled out. When you recharge the system on any a/c I think its best to evacuate the system completly and put a vacume on the system for a minimum of 30 minutes. This helps release any trapped refrigerant and remove any moisture from the system. I have seen that after a charge without following this rule the system bled out through the low pressure service port. Thus rendering the a/c system ineffective overnight.
If there is a blocked orifice it should be easy to see because your tubing around it will ice up on the outside. Most commonly I think a/c problems stem from in inadequate or overservicing of refrigerant. I would get a second oppinon from a a/c technician. Just my two cents. Good luck.

 

[budwich]

Well I will give my "unexperienced opinion"... first, IF your observation is correct (ie. the fan is running at normal speed... ie turning as it should...) and you are then noticing a reduced air flow as your problem begins to occur, that would indicate a blockage along the path. IF the blockage is "associated" with your AC evaporator freezing up, then I do believe the most likely cause of that is over filled refrigerant. My understanding is that a blocked / clogged orifice would result in less cooling (and hence no "freeze up") and in addition would cause your low pressure switch to operate because insufficient refrigerant would be making its way back to the compressor (hence the "low pressure" condition). So a question / test: IF when the condition occurs, and leave your fan speed alone (ie. at high) and switch from "AC setting" to "heat", what happens???? you should get relatively hot air and the flow should be "normal" (ie "full capacity"... blow your hair off). ... and you might hear some doors switch (important observation). IF no "blast" of air flow occurs (assuming the fan speed is functioning) then it is likely your evaporator is frozen and as stated earlier, you have an "overfill" problem.

 

[Cobraguy]

I agree with budwich. This really sounds like the evap is freezing up. Like he said...switch to heat for a while and see if it doesn't come back. Also, make sure the case is draining properly. If it works for the first part of each day, then there is no leak. And one last test...when you lose your cooling, check that the compressor clutch is engaged and the compressor itself is turning. If it is, you're frozen up. That's a problem I'd like to have right now!!

 

[Evil Eye]

If it is, you're frozen up. That's a problem I'd like to have right now!!

Yeah, I agree!!! 106 for the past few days has been brutal with the humidity.

 

[pmacaula]

Thanks everyone. Am going to another shop.

Am fine fixing boats and bodywork, but this stuff is outside my skill set.

Will report on any further developments of interest.

Cheers. Patrick.

 

[Cobraguy]

Yeah, I agree!!! 106 for the past few days has been brutal with the humidity.

You got that right. Dry heat my a$$. Got up at 4:00 the other morning to go work on the car. The temp was 94 and the humidity was 77%. It just got worse from there. Monsoon season sure isn't fun. Can't wait for September. Temps will be in the one teens again...but the humidity will be gone.