Strange AC issue

[bigceltic]

First of all, I have done multiple searches but not found my particular issue so I figured I'd start a new thread.

My issue just started two days ago. Up until then, no issue at all. Issue involves my AC and it worked fine on the way to work on Tues, but not on the way home! Symptoms are that when I turn AC on, it blows outside temp air - not like the heater is on, but rather ambient, which happened to be in the 80s both Tues and yesterday - from all vents - I have dual zone and both are set to cool. I tried cycling the knobs and switches but no change. Turn everything off, and then continue driving home. Tried it a couple of more times - no change, off for a bit, back on, no change, until I left it off for about a full 10 -15 mins and try again and voila!, it blows nice and cold from all vents. Works perfectly. Next day (yesterday) try AC on way into work, same issue - outside temp air. Turn off. Try it a few mins later, no change. Wait a while (10-15 mins) and try again - nice and cold! Rinse and repeat on way home! What the heck?

I don't think it is the dreaded blend door issue as the issue seems to affect all zones. Any ideas? I am going to take it into the shop next week, but if there were some obvious thing I could check and or fix, I would like to know.

Thanks in advance,
George

 

[Ozymandias]

Freon low i would guess.
Low pressure switch shuts off and after some time the pressure in the system levels out and allows another short compressor run cycle till it shuts of again.

 

[bigceltic]

Freon low i would guess.
Low pressure switch shuts off and after some time the pressure in the system levels out and allows another short compressor run cycle till it shuts of again.

Thanks, I will see if I can refill myself (I thought I read that I could do so pretty easily). Appreciate the help!

 

[Ozymandias]

You can, its easy - just one thing - take ONLY pure R134A - without any sealer or other stuff in it.
If you would fill that in - no technician would ever touch that system again in the future.

 

[bigceltic]

You can, its easy - just one thing - take ONLY pure R134A - without any sealer or other stuff in it.
If you would fill that in - no technician would ever touch that system again in the future.

Ok, will do. Thanks.

 

[AEdelheit]

I fill mine but bought a gauge set to watch the pressures and not overfill it, even the Harbour freight set is decent enough for the occasional top off.

 

[BigPapa]

If the charge is low, it went somewhere.......

 

[bigceltic]

If the charge is low, it went somewhere.......

Yeah, I guess there is that. Maybe I will just get it in to get it tested.

 

[Ozymandias]

You can, but if it is still factory fill, 14 years old, then it is common to need a recharge.
I would give it a try.

 

[bigceltic]

You know, I am having a heck of a time finding a recharge kit that does not have sealer and or dye in it!

 

[Ozymandias]

Homedepot, Napa, O'Reilly, Advanced, have seen them in all of the Shops.

https://www.homedepot.com/p/12-fl-oz-Canister-Refrigerant-R134A/302287969

 

[bjgillisva]

I'm having a similar problem with the AC being hit or miss. It finally went out on me and I am trying to refill the system but the compressor only engages 3 short bursts when turned on. Is there a way to jump the transducer on these to get the compressor to engage to allow the refrigerant to fill?

 

[bigceltic]

Homedepot, Napa, O'Reilly, Advanced, have seen them in all of the Shops.

https://www.homedepot.com/p/12-fl-oz-Canister-Refrigerant-R134A/302287969

Oh, ok. I had been looking at the ones with built in gauges and hose. I will re-look. Thanks, Ozy.

 

[Ozymandias]

Na these are sold separately but together still cheaper then the combos, and you can always recheck the filling with just the gauge adapted to your system.

 

[bigceltic]

Brakes Plus had a free AC check service, so I stopped by on the way home from work today, and they said the compressor was not running - although I saw it running when I pushed the AC switch when I was investigating last night (I also checked the wires for any rubbed or frayed spots- none). They also (free of charge!) added about 1/2 pound of refrigerant and tested for leaks - none found and they were not able to get the AC to work, although on the way there, my truck did its usual - not working at first, then after a couple of tries and multiple minutes the AC worked fine! Ugh. They wanted to keep it and do some more testing, but I took it back to see if the connectors for the controls were not fully seated from when I changed out the stereo. I just checked and the plugs on the back of the HVAC controls are properly seated, and the fan speed control works and the indicator lights light up on the buttons. While in the garage testing it (in park), when I pushed the AC button, the engine did do a little bit of surging which was new (did not notice that last night). After a couple of tries, and then revving the engine, the AC kicked in. I am thinking electrical, but before I drop $300 plus on a new HVAC switch cluster, I figured I'd see if there were any other ideas.

 

[dieselshadow]

It sounds like the clutch is going out to me.

 

[JR]

Perfect time to buy some new tools! HF has a pretty decent manifold so you can actually watch your pressures to help in diagnosing. This is a bare minimum requirement IMO. Can also be used to evac, pull vacuum and charge if you should ever choose to equipment up in the future. You really need to see what your pressures are doing to help diagnose your problem. You may have over charged your system without knowing for sure what is going on. 8 oz is quite a bit without knowing exactly what is in there to begin with which is impossible without evacuating and recharging.

https://www.harborfreight.com/AC-R134A-Manifold-Gauge-Set-62707.html

And 25% off Labor Day coupon


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[DavidC]

I would say your charge is borderline. As you drive heat is built up in the engine bay which will raise the freon pressure slightly so it will work warmed up but not a cold engine. If left alone eventually it will not work. I had the same problem once that the gauges confirmed, added a few ounces of freon problem solved.

 

[RVTRKN]

To see what the refrigerant is doing without gauges, is easy but not accurate. First things first, that was foolish to put a 1/2 pound of refrigerant in a system that may be fully charged. Espeacily when no leak was found, that means the tech was guessing.

When the truck is idling with the blower on high and with a warm cab, the compressor clutch should stay engaged running the compressor. Next feel the temperature of the refrigerant line going into the firewall, it should be real cold. Then feel the the temperature of the filter accumalator line leaving it. They should both feel cold, if they are, you may have a blend door issue.

Back to the charging of the system, now that you know your refrigerant charge isn't accurate, and you know this because the tech charged some in, it'll have to be recharged with the correct amount. The easiest way with minimal equipment, is dump SLOWLY (note the word slowly) as not to let any oil escape. Let it out until just above 0 psi, then weigh in the correct amount, which should be given on the data plate. Scales and refrigerant containers vary, and more likely you dont have either, you may want to have a professional trouble shoot the system, recover and evacuate the system and charge the correct amount. That way they know the charge is correct, and will help in diagnosing it.

 

[Tuesdak]

It sounds like the clutch is going out to me.

X2 or the compressor is trying to lockup and surging the engine. Compressor lockup will torch the clutch and belt, but, not match for the mighty Cummins that will keep on running as things get "interesting".

Probe the wires to the compressor clutch: Does it have 12v? If so you have a mechanical, not electrical, problem. A worn out clutch may have 12V and not start the compressor spinning. Oil leaking on the clutch or from a badly leaking shaft seal can also slip the compressor clutch.

Does the clutch look like it's been hot from slipping?