A/C blows warm when stopped

[nuts4hotwheels]

My a/c blows cold at highway speeds but warm when I stop in traffic.

I hooked manifold gauges to it and High and low sides are both around 60 as you can see in picture.

Condenser is clean and fan is blowing good.




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[brad325is]

weak compressor? Cooling fans not spinning freely?

 

[Arth]

Your high side is really low. Like the condenser isn't doing it's job or you could be low on Freon.

Look at this video. He's "topping off" his AC but he started with cold air. His high side is much higher. I'd wait for others feedback but you've got something not doing it's job sitting there.

 

[crash68]

If the high and low side pressures are the same when idling and the compressor is running, there is something wrong with the compressor, maybe a wasted discharge valve. It's possible an issue with the metering device but unlikely? What happens with the pressures at 2K rpms?
If the condenser wasn't doing it's job, the high side would be excessively high, not low.

 

[nuts4hotwheels]

What should I check next?


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[kiloRAM]

My old 2004 RAM did the same thing. As soon as I stopped, the AC would blow hot air. When I started moving again (probably >10 mph), the AC would blow cold again. My issue was caused by the condenser fan not working. Once I replaced the fan, it worked like a charm. It was relatively easy to replace.

BTW, the condenser fan is different than the radiator fan. I'm not being a jerk, but mentioning it just in case you didn't realize there are two fans.

Good luck. I hope you are able to track down the isue.

 

[WilliamS]

That high is way too low, either you have a clog in the system somewhere, or the compressor is on its way out. Im going to go with compressor, they are relatively cheap, and easy to replace.

if the fan isnt running full power with the AC on this could also cause this issue.

 

[cody mummert]

check the fan my 03 went out had the same issue

 

[nuts4hotwheels]

It turns out that I was doing something wrong with gauges. I hooked it back up to check again and it was a little low on refrigerant. I added a little more and it is cooling about 40 degrees cooler than ambient temperature. I must have made a stupid mistake


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[nuts4hotwheels]

I did more investigating and discovered that the fan was working but was wired backward by previous owner. So, it was running in reverse and blowing hot air from the engine bay across the condenser instead of sucking in outside air.


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[cat199]

The things that people have installed wrong or wired incorrectly are some of the most difficult to troubleshoot and correct. And Thank You for posting what you found Good job

 

[brad325is]

or that....ha

 

[nekkidhillbilly]

look at your recirc door too. those things suck.

 

[Outdoors76]

I did more investigating and discovered that the fan was working but was wired backward by previous owner. So, it was running in reverse and blowing hot air from the engine bay across the condenser instead of sucking in outside air.


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now that is aggravatin' but at least it was a cheap fix! nice find!

 

[nuts4hotwheels]

now that is aggravatin' but at least it was a cheap fix! nice find!

Yeah, I kept looking at the fan and it was working and then I realized that it might not be spinning the right direction.


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[Cool_Hand_Luke]

It turns out that I was doing something wrong with gauges. I hooked it back up to check again and it was a little low on refrigerant. I added a little more and it is cooling about 40 degrees cooler than ambient temperature. I must have made a stupid mistake


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I think you did your test with engine and/or compressor off. When the compressor is not working, both low and high side will equalize and display the same pressure.