AC shuts off when idling in traffic

[Dutra]

Dodge is the gift the keeps on giving! Another problem! With my last fiasco, I'd rather avoid the stealership.

2018 Ram power wagon 6.4 with 44k miles. Ac works just fine when driving. When sitting in traffic for about 20 mins the AC no longer blows cold air. Then it gets to room temp to nothing. Temp gauge slowly starts to creep up in temp. When traffic gets better the gauge drops and the ac is cold again. Any thoughts? Yea I know, shouldnt have bought a dodge.

 

[indept]

How hot is the outside temp? Is the E-fan on?

 

[chopperman1]

Sounds like a fan issue to me. If it were just the AC I would suspect low refrigerant but where truck temp climbing too, tells us the electric fan is not coming on.

 

[Dutra]

How hot is the outside temp? Is the E-fan on?

Mexico, 119 degrees. But at 90 degrees same thing happens. I'm thinking the E-fan is not turning on. I checked the fuse and nothing wrong there. Going to a buddy's house later this week and checking with a volt meter see why its not kicking on.

 

[Dutra]

E Fan is working properly. We manually got the fan to turn on and off and there is plenty of coolant. No fuses or relays are blown.

 

[Dutra]

Anyone have any ideas?

 

[bm02tj]

The fan needs to come on automatically
Drive till hot with ac on then stop and see if E fan comes on before ac stops

 

[emjohn4]

Does your truck have the aero grille? The one with the flaps that close at highway speeds?

If so, any chance they are 'stuck' closed?

If your efan is working, that's the next thing I'd check.

 

[Black1500Ram]

Mechanical fan clutch could be bad or bad thermostat (not opening).

Coolant should never reach 230° no matter the ambient temp unless under heavy load like towing. 200°+ trans temp is also concerning IMO.

If coolant is of the proper type and at proper 50/50 mixture, with no air in the system, then there’s not enough of a fluid moving across the radiator, either air or coolant.

Easy way to test the tstat is to take it out and drop it in a pot of water on the stove and watch to see if it opens once the temp gets to the right #. I do this on all new tstats before installing. I’ve had brand new ones be bad.

 

[04fxdwgi]

AC kicking off when hot outside air is usually sign of high pressure on the refrigerant (high head pressure switch kicking it off). That is usually a sign of low air flow over AC condenser (unit in front of radiator).
Closed shutters
Filthy / blocked AC condenser coil
Bad air circulation fan (Usually the electric one not kicking on, but can be either.)

PS: The electric is also supposed to come on to assist the clutch fan when engine temp gets over a certain temp (think it's 203)

 

[RamDiver]

PS: The electric is also supposed to come on to assist the clutch fan when engine temp gets over a certain temp (think it's 203)

Shouldn't the electric fan also kick on immediately when set to Max AC?

I agree with the potential AC Condensor-related problem. I've seen this fault description where the AC only blows cold when the vehicle is moving, not when stationary.

To the OP, have you tested the AC functionality while set to Max AC?

.

 

[RamDiver]

E Fan is working properly. We manually got the fan to turn on and off and there is plenty of coolant. No fuses or relays are blown.





View attachment 532657

What were the ambient conditions when this picture was taken and was this while towing?

I believe you may have 2 issues.

First, I would check for the airflow over the rad.
Do you have active grill shutters that are failing to open?
Is the rad coated in dirt or gunk that prevents sufficient airflow?

If both these are not a problem, your thermostat may not be opening soon enough.
If you monitor the coolant temperature, you should see a rise to ~210°F, then a quick drop to about 206°F. That's with the stock thermostat on my 1500, it may be different on your PW but you should still see cycling action from when the thermostat opens & closes.

The description that the AC only functions when the vehicle is moving suggests the E-fan or AC Condensor is not working correctly.
Is the condenser unit coated in dirt or gunk?
Does the E-fan come on immediately after switching to Max AC?
How well does the AC function when set to Max AC?

.

 

[turkeybird56]

Shouldn't the electric fan also kick on immediately when set to Max AC?

I agree with the potential AC Condensor-related problem. I've seen this fault description where the AC only blows cold when the vehicle is moving, not when stationary.

To the OP, have you tested the AC functionality while set to Max AC?

.

Switching to MAX< the AC fan should come on. Did so on my 2015 ED, and does on MY 19. Actually, when really hot out, when I "park", before coming in driveway, I set the AC to max to force on the AC fan on so the system cools down a bit before I park. BU I am no mechanic and definitely not HVAC/Auto AC expert, just my situation, especially when the temps outside get over 100F and stay there, as we all know these AC systems not the best. (IMHO)

 

[Dutra]

What were the ambient conditions when this picture was taken and was this while towing?

I believe you may have 2 issues.

First, I would check for the airflow over the rad.
Do you have active grill shutters that are failing to open?
Is the rad coated in dirt or gunk that prevents sufficient airflow?

If both these are not a problem, your thermostat may not be opening soon enough.
If you monitor the coolant temperature, you should see a rise to ~210°F, then a quick drop to about 206°F. That's with the stock thermostat on my 1500, it may be different on your PW but you should still see cycling action from when the thermostat opens & closes.

The description that the AC only functions when the vehicle is moving suggests the E-fan or AC Condensor is not working correctly.
Is the condenser unit coated in dirt or gunk?
Does the E-fan come on immediately after switching to Max AC?
How well does the AC function when set to Max AC?

.

Not towing anything I am afraid to with this truck lol. Rad is clean and nothing blocking the path for air to flow. That pic was taken in Mexico, idling in traffic for around 30 mins. 110 degrees outside maybe hotter. E-fan works just fine I tested it. The condenser is also very clean. The thermostat might not be opening soon enough but I know it does work or the truck would have overheated in that traffic. Also this truck has 52,000 miles on it now.

 

[62Blazer]

The engine getting hot while sitting still is almost always because the cooling fans are not working correctly. Sitting at idle the engine puts out the smallest amount of heat as possible because it's not working hard, but the problem there is no air being forced through the radiator if the fan is not working. When running down the road the engine is making a lot more heat but is basically having air forced through the radiator at speed. So again, if the engine gets hot sitting in traffic and then cools off when getting up to speed it's almost always the fans. If it was the thermostat it would get hot driving down the road also. If the fins of the radiator were clogged it would have more of a tendency to heat up when driving.

The AC stopping is because the engine is getting hot. Part of it is simply as the engine gets hot it doesn't cool down as well, and usually modern vehicles will turn off the AC if it starts getting got. The AC system puts more strain on the engine and keeping it on will make the engine even hotter.

 

[RamDiver]

Not towing anything I am afraid to with this truck lol. Rad is clean and nothing blocking the path for air to flow. That pic was taken in Mexico, idling in traffic for around 30 mins. 110 degrees outside maybe hotter. E-fan works just fine I tested it. The condenser is also very clean. The thermostat might not be opening soon enough but I know it does work or the truck would have overheated in that traffic. Also this truck has 52,000 miles on it now.

You didn't mention if the Max AC setting changed the AC performance or not. And, if the E-fan starts immediately after setting to Max AC. This information could be important details to know.

If you have no airflow issues and the fan is working correctly, I still have to wonder about the thermostat. If it were opening late, at a higher temperature, the temperature recovery might be compromised.

Could you monitor the coolant temperature and try to identify the temperature cycle range? Then we can guesstimate the thermostat temperature and decide if it's typical or not.

Also, when your AC is blowing warm air when stationary, is the coolant temperature always high?

.

 

[Dutra]

Coolant is always high I check a lot. The AC is on max when driving freeway speeds works great. When I get to traffic in hot temperatures while idling for awhile, the AC starts to warm up to where there is no longer cold air blowing. More like room temp. And the gauge on the dash starts to move, then flicker from 1/2 to 3/4. I get nervous and stop the AC immediately.

I can hear the fan kicking on when the max AC is pressed at a stop sign or when I first turn on the truck. But when in traffic I am not sure I hear the fan stay on

 

[RamDiver]

Coolant is always high I check a lot. The AC is on max when driving freeway speeds works great. When I get to traffic in hot temperatures while idling for awhile, the AC starts to warm up to where there is no longer cold air blowing. More like room temp. And the gauge on the dash starts to move, then flicker from 1/2 to 3/4. I get nervous and stop the AC immediately.

I can hear the fan kicking on when the max AC is pressed at a stop sign or when I first turn on the truck. But when in traffic I am not sure I hear the fan stay on

I would say the first order of business is to sort out why the coolant temperature is always high.

If the coolant system is not functioning, there's no point to chasing an AC fault.

If you watch the temperature gauge often, it shouldn't take long to determine where the temperature cycle begins and ends.

I'm guessing that your truck will be somewhere around 195°F to 205°F +/-.

I believe my truck's temperature cycle is a bit lower than I previously mentioned but I do recall that the highs and lows are quite apparent while I'm driving during the summer or winter.

Please update this thread when you figure out where the temperature cycle is on your truck.

Have you confirmed that your truck doesn't use the Active Grill Shutters and there's a clear open path through to the grill to the rad?

When was the last time the coolant system was flushed?

Sometimes we can leave an air pocket that will cause cooling grief.

Check this video on purging air from the coolant system.

More than one way to bleed a Hemi coolant system

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[04fxdwgi]

Shouldn't the electric fan also kick on immediately when set to Max AC?

I agree with the potential AC Condensor-related problem. I've seen this fault description where the AC only blows cold when the vehicle is moving, not when stationary.

To the OP, have you tested the AC functionality while set to Max AC?

.

Yes, absolutely. Was trying to highlight that he should have had it at 203 (or something like that), also

 

[Lsujker]

At this point, could care less if the AC works or not. Don't burn the motor up. That's your focus now.

My E fan comes on 10 seconds after starting the truck every time. Motor hot or cold. hard to hear from inside. Replace the clutch in the mechanical fan and report.