2nd Gen Non-Engine/Transmission Intermittent ac issue 2001 6 spd HO Quad 4wd

[Conley]

I am having difficulty figuring out why my ac blows cold initially and then stops cooling. If I turn it off for 5 minutes or so, it will blow cold again for about ten minutes. If the outside temperature is below 80, I don't seem to have the problem. Even at it's coldest, it's only cooling down to about 50 degrees at the dash vent. I've swapped the a/c clutch relay with another to no avail. It would seem that some part of the system is freezing up, and by turning the a/c off it defrosts and works again for a short time. I don't think the evaporator is freezing up, as I would think that would show up as a reduction of air volume from the dash vent. I don't hear the a/c clutch cycling on and off like I think I would. Thanks, Chris

 

[JLandry]

Chris,



According to the Dodge service manual, the AC low pressure switch (which is located on top of the accumulator) controls minimum evaporator temperature and prevents the evaporator from freezing. It does this by cycling the compressor clutch on and off.



With the symptoms you've described, and since you aren't hearing the compressor clutch cycle as expected, maybe the low pressure switch needs to be replaced?



The switch should be vailable from your favorite local auto parts store for around $20 or less. The Dodge part number is 5018449AA and costs just under $30 at Mopar-wholesale.com.



The service manual says the low pressure switch is installed hand tight only. It has an o-ring which supposed to be lubricated with clean R134 compatible refrigerant oil.



Regards,



John L.



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[Conley]

Thanks John. I'll try replacing the low pressure switch. If that doesn't work, I'll buy a 134 manifold gauge set, as diagnosing without one seems impractical. Chris

 

[DSeamans]

Gauges

Yes, you HAVE to have gauges! To me it sounds as you may be overcharged a little. The hotter the ambient temp, the higher the high pressure. If you have just a little too much coolant in, it won't blow very cold, then the high side gets over 300# and the high limit shuts it off. Then nothing til it bleeds back down.



Troubleshoot Automotive Air Conditioning Problems



This link has a chart that tells most of what you need. Good luck,



Dave

 

[Matt42]

Yes, you HAVE to have gauges! To me it sounds as you may be overcharged a little. The hotter the ambient temp, the higher the high pressure. If you have just a little too much coolant in, it won't blow very cold, then the high side gets over 300# and the high limit shuts it off. Then nothing til it bleeds back down.



Troubleshoot Automotive Air Conditioning Problems



This link has a chart that tells most of what you need. Good luck,



Dave

What Dave said is true. DO NOT try to save a few bucks by buying the gauge set from Harbour Freight. I did and it was a mistake. Spend a few bucks extra and get a Robinair or another name brand. You won't regret it.

 

[Dan_69GTX]

Things to check:

- when the a/c stops blowing cold, does the compressor still run? (you say you don't hear it cycle, but you didn't answer the question of is it running? If not you have one of the following: Bad A/C clutch coil, bad relay(you already replaced that you said), bad high pressure switch (or it's working and you have high pressure), bad low pressure/cycling switch (or you are under charged or have other issues), bad wire(s) (power feed).



- Ever have the a/c worked on - if so what was done?



If the system was opened and a good vacuum not drawn (30+ min down to less than 1000 microns of vacuum) there could be moisture in the system. Moisture will freeze at the expansion orifice and stop cooling.



Did you or anyone ever add sealant (very very bad!!!) This causes all sorts of issues and will void any warranty. There are 2 types of sealant - moisture/air activated (very very very very very very bad) and seal swellers (very very bad). These void any and all warranties from anyone. I check for them before I work on a system and will not touch it if found and I label the vehicle that it has sealers in it.



Does this happen when driving, sitting, both, etc?



If you have high pressures have you checked your fan clutch?



If you had it worked on, does it have R-134a? Most shops don't have a refrigerant identifier (infra-red spectrometer) and will such crap from one vehicle and spread it to all others (just like they do sealants). All sorts of stuff can happen if the system doesn't have the right refrigerant.



Did someone overcharge the system with oil? These only take a few oz of oil.



Also - FYI - a low charge will not properly circulate the oil and will starve your compressor - want to save your compressor? - don't let your system run a long time with a low charge. Of course a overcharge will over tax the compressor.



When hooking up gauges, just turn the knob on the valve until you see pressure on the gauge - then turn a LITTLE farther. I've seen where folks hook up their gauges, crank down the valve all the way and bend the schrader valve. Some can be replaced on the vehicle (with the right tool), some need the refrigerant removed, some need the hose replaced. Just a warning for you.



A professional mechanic trained in A/C repair with the right tools can help you. However, most don't have training, have minimal tools, and don't have a clue what they are doing. (sorry - had to rant a little - it just ticks me off when I see people getting screwed by these types).

 

[Dan_69GTX]

PS - Hi Conley - welcome to a wonderful site with lots of resources. Fill out your signature so we know where you are from, what truck you have, options, etc. The search feature is GREAT. It's best to use the search feature before asking too many questions but if you can't find what you are looking for, ASK!!

 

[Dan_69GTX]

Oh yea - you stated 50 degrees at the dash vent - but you never stated if that was idling, running down the road, fan speed, recirculate or not, outdoor temps, how long it was running, humidity, center or side vent, etc.



All that affects your vent temp, so, 50 degrees could be normal (unless it was Celsius):-laf

 

[super38]

I had the exact same thing happen a few years back on my '01. Turned out to be the AC clutch, it would work for 5 to 10 min then quit, the coils would heat up and open and after it cooled for another 10 to 20 min it would work until it got hot again.