My A/C blows ice cold for about an hour (sometimes shorter sometimes longer) then blows warm and usually stays that way. Any ideas? I don't know much (anything) about A/C systems...

 

The evaporator might be freezing up(forming ice on the coils). Then air cannot pass through the coils, so you cannot remove the heat out of the air. Also a/c systems at max potental will cool air about 30 degrees cooler than outside air.

 

Probably what Ram2940 said. Try to run the fan at a faster speed and set the temp control to wherever you are comfortable and see if that helps your problem.

 

Hmm, I guess I forgot to mention this is cruising at 70 MPH in 100 F heat. I don't think ice can form (?).

The blower motor is at level 3 out of 4, I have the temp control set at COLDEST, and the air is VERY COLD for a long time, then all of a sudden turns hot. No change in speed marks the change in temperature.

 

Yes, ice can form. Actually, if you are low on freon you can ice up the coils rather fast.

You need to turn your thermostat down also, and like the previous post says you might want to try turning you fan up. Running an hour at full cooling is what is icing it up. It needs a break now and then. If it keeps it up you need freon.

 

I wouldn't be surprised if I'm low on freon. How can I check this and refill it myself?

 

Matter of fact, I just added freon to my system today. I went to advance auto and bought a low pressure guage(looks like a gun with guage on back, can screws into the bottom and has a trigger to put freon in, release trigger and it reads pressure $19.95). Pressures will go up as outside tempature rises. Guessing if it is 100 low pressure would be around 45 to 50 with the compressor running. At 70 degrees pressure should be around 35 psi. Remember that the compressor needs to run for accurate pressures. You test at the low pressure fitting(close to fire wall on passengers side by air filter box).

 

OK so I just buy a thing that'll read the pressure, check the pressure and fill it until it hits 45 - 50 PSI?

 

If you haven't done it before I would not try it myself. If you hook up to the high pressure side the can will explode. Do you have a buddy that has A/C experience?

I would try turning the thermostat down first.

 

When it starts blowing warm, check to see if the lines, receiver/dryer etc. have ice on them. If you compressor doesn't cycle because of a faulty pressure switch or something like that it will behave in the way you describe.

 

On the bad side, find someone with a freon detector and put it in the pee hole and see if it goes off.

Dodge changed the evaporator materials in the late 90's and they have not been worth a dang since then.

Dave

 

Must've been after '97. Owned the truck 3 years, and it is still nice and cold. Haven't done a thing to it..

 

I think in 98 with the 24V engine for what ever reason. My sons 96 has never had a problem with the A/C and works fine at 250,000 miles. I knew I should have kept that truck.

I have put two A/C compressors and dryers in mine along with an evaporator. That amounts to almost $ 2,000.00 in additional operating expense since 2000. I've got 143,000 on mine now.

Dave

 

Can anyone tell me how long it should take to increase the pressure?

I was at about 30 PSI and I want to bring it up to about 50 PSI I think...

I have an 11 OZ can of r134a and I sat there for like 10-15 minutes and its still not empty and the pressure only increased to about 35 PSI,.. Is this normal???

 

Normally pressures wil increase as outside tempature rises. If outside temp is about 75, 35 to 40 psi should be about right. Main thing is A/C getting cold, because you cannot go by pressure alone.