Strange Intermittent AC Issue

[StevesRam1500]

Hello everyone! My name is Steve, and as of Friday, the new owner of a 2020 Ram 1500 Limited 4x4. Absolutely LOVE the thing and is pretty much my dream truck.

Anyway, on to the issue.

From the moment we took possession last Friday, driving home (the dealership was about 50 miles away), the AC was working wonderfully. Then it seemed to start blowing less and less the more time went on. By the time I was about 20 miles from home, it wasn't blowing at all. The dash vents, seat vents, nothing.

However, you could still hear the blower under the dash. Tried literally every setting, off/on, etc, and nothing helped.

As soon as I got home, and we were going to go get some dinner, started the truck and the AC worked fine again.

This morning, going to church, after we were about 15 minutes from the house, it did the same thing again. Blowing slowly started getting less and less (takes about 10 or so minutes before it gets to the point of totally stopping blowing) until it stopped blowing air. Still can hear blower under the dash.

After church, going to lunch, worked fine and worked fine the whole way home again.

We live in central Florida and it's already been in the 90's so having an AC we can't depend on isn't something we need to have hanging over our heads.

Has anyone had anything like this happen before?

Thank you all for any help you can give!!

Steve

 

[User_3336]

Have you searched and read any of the other 1,000 + posts on this forum about a/c issues on the RAM?????

 

[StevesRam1500]

Definitely had seen a few, but perhaps not enough to find this specific issue.

 

[Richard320]

My guess is that the evaporator is icing up because of the humidity. There's supposed to be a sensor that tells it when it's getting close and it stops the compressor momentarily to let it defrost. Until you can get the truck back to the dealer, try running it in recirculation mode. Then the humidity inside will condense and drip away (hopefully) and you won't be bringing too much more in.

 

[StevesRam1500]

My guess is that the evaporator is icing up because of the humidity. There's supposed to be a sensor that tells it when it's getting close and it stops the compressor momentarily to let it defrost. Until you can get the truck back to the dealer, try running it in recirculation mode. Then the humidity inside will condense and drip away (hopefully) and you won't be bringing too much more in.

Hi Richard,

Thank you very much for taking the time to reply.

Would this result in the air not blowing at all (or slowly decreasing until it's not blowing over about 10 minutes)? I could be wrong, but if it was the compressor, wouldn't it just not be cold, but at least blowing air? In this case, it just stops blowing air slowly.

Thoughts?

 

[StevesRam1500]

And I should add that it doesn't start getting cold again until after we've turned off the truck and turned it back on.

 

[Mountain Whiskey]

Is it set on Auto or in your radio, Max Cool? Ever check the coolant charge? Just suggestions to look at.

 

[theblet]

Low can coolant will cause an ice over. U have warranty left?

 

[Sascwatch]

Could also be a dirty cabin filter restricting airflow or clogged drain on the evaporator.

Cabin filter will be located behind the lower glove box, which you have to remove to access the filter.

You can check the drain for the ac pretty easily aswell, open your hood and you should see where the drain comes out of the cab on the passenger side firewall. There is usually a short rubber elbow on the drain to help guide the water out, you can remove the little elbow and try poking a short zip tie or something in there to see if it is clogged. I would avoid using anything to hard to avoid damaging the ac evaporator.

If neither of these fix the issue you may have low refrigerant levels. Which will require a licensed tech to recover the existing refrigerant and refill it to the proper level.

Just an fyi on the “cooled” seats, they don’t actually blow cold air out of them, there is a fan that sucks air through the seat that is separate from the hvac system.

 

[theblet]

Also, if your system is freezing over, you’ll see ice on the suction line under the hood. Should be the larger line.

 

[StevesRam1500]

You all have given me a lot of awesome information to check on and I thank you kindly!

For context, I've had it since Friday. It is a 2020 with a little over 14,000 on it and we do have a warranty left on it.

I've tried all different settings when this is happening (has happened twice in two days). Max AC or other settings make no difference other than sounding like it's blowing harder under the dashboard, but not actually blowing air out of the vents (any vents, not just driver).

 

[Mountain Whiskey]

Licensed tech. Phhhht. Put a set ot gauges on it. If it reads low, you don't need to recover anything, just hook up a can and add a bit. When you hit the right pressure for the temp outside, you are good. Pretend you didn't release the rest of the can to the atmosphere.

For heavens sake don't let this girl find out if you do!

 

[Ram4Lou]

Hi Richard,

Thank you very much for taking the time to reply.

Would this result in the air not blowing at all (or slowly decreasing until it's not blowing over about 10 minutes)? I could be wrong, but if it was the compressor, wouldn't it just not be cold, but at least blowing air? In this case, it just stops blowing air slowly.

Thoughts?

I concur with Richard as this being a possible cause. The evaporator coil would slowly build ice, which would incrementally cause more and more restriction of air-flow through the coil box, up to the point that the ice builds up enough to completely block air-flow. You would still hear the fan running because these are typically squirrel-cage fans that can run effortlessly in a restricted air condition, however no air would be moving through the ducts. Next time it happens, use Richard’s suggestion of running the fan on high in recirc with the AC turned off. You should feel the air-flow slowly increasing as the ice melts.

On home AC units, this is typically caused by low Freon levels or dirty evaporator coils. however, since your truck is fairly new and the air-flow starts off good, it is probably not a dirty evaporator coil. You probably have a Freon level issue or a faulty sensor.

 

[Richard320]

Hi Richard,

Thank you very much for taking the time to reply.

Would this result in the air not blowing at all (or slowly decreasing until it's not blowing over about 10 minutes)? I could be wrong, but if it was the compressor, wouldn't it just not be cold, but at least blowing air? In this case, it just stops blowing air slowly.

Thoughts?

The evaporator looks like a radiator. The cold flows through the tubes and the air flows through the fins. So as ice starts forming on the fins, the air flow gets less and less. You may also notice the air out the vents actually getting warm and humid before it completely stops. Once the truck is off, no more cold, so the ice melts, and once again you get air flow.

Run the AC in recirculation to minimize the moisture that can freeze on the evaporator, and if it does start to slow, shut off the AC but leave the fan on and it should melt away in a few without having to shut off the truck.

Until you can get it back to the dealer to get this dealt with.

 

[StevesRam1500]

REALLY appreciate all of you taking the time to respond!! And that is a great thing to try.

I do have an appointment Wednesday for them to check it out, but in the meantime, this is something I'll try as a troubleshooting step if it happens again!

Really glad to have joined the forums!

Steve

 

[StevesRam1500]

Hi again everyone,

Just wanted to follow up.

First took the truck in and they replaced a relay (not sure which one). On the way home, the AC I would say is definitely working better.

However, there were several of you who mentioned the condenser icing up which might be the culprit. I think this might be what is going on.

Once I could feel the air start to slowly drop off, I would hit the AC button to turn it off but left the fan blowing, and within about 10 second, the air was moving just fine again. I let it go until it started feeling a bit warmer than the cabin temp and then turned it on again and it worked great for quite awhile. Had to do this 3 times on the way there and maybe once on the way home. But the one on the way home didn't fully stop blowing, so maybe that was me.

In any case, is this expected behavior? It was 80's on the way to Tampa today with reasonable humidity. Was over 90 on the way home.

If it's expected, at least I know what to do to get it to work again. If not, and they replaced a relay, what else could be causing this?

Thanks again everyone!

 

[Mountain Whiskey]

Hi again everyone,

Just wanted to follow up.

First took the truck in and they replaced a relay (not sure which one). On the way home, the AC I would say is definitely working better.

However, there were several of you who mentioned the condenser icing up which might be the culprit. I think this might be what is going on.

Once I could feel the air start to slowly drop off, I would hit the AC button to turn it off but left the fan blowing, and within about 10 second, the air was moving just fine again. I let it go until it started feeling a bit warmer than the cabin temp and then turned it on again and it worked great for quite awhile. Had to do this 3 times on the way there and maybe once on the way home. But the one on the way home didn't fully stop blowing, so maybe that was me.

In any case, is this expected behavior? It was 80's on the way to Tampa today with reasonable humidity. Was over 90 on the way home.

If it's expected, at least I know what to do to get it to work again. If not, and they replaced a relay, what else could be causing this?

Thanks again everyone!

I thought we went over what would cause the condenser to freeze up. Low freon.

 

[theblet]

Not the condenser, the evaporator.

 

[StevesRam1500]

Not the condenser, the evaporator.

Would this be expected behavior for the evaporator?

 

[theblet]

Would this be expected behavior for the evaporator?

With low refrigerant, yes. You will also see the suction line and receiver drier freeze up. Good indicator because you can’t really see the evap core because it’s in a housing in the dash.