A/C only blows cold while driving

When tracking down electrical issues you can have proper voltage and NOT proper amperage in high amp draw situations.

 

Mine does exactly this. Above 2500rpms parked it blows ice cold but not at idle. What causes this? Also, same thing at higher speeds it's ice cold. Cleaned the condenser and the fan seems to have proper resistance.

 

Randy87, first off this is the 1st gen forum, most peeps here are familar with the 1st gen trucks, yours is differrnt enough to be differernt enough, having said that, they ALL operate on the same principal, open the hood and and look at the AC condensor, follow the aluminum lines, somewhere you will see an aluminum can type device, there should be sight glass on the top, clean it and tell us what the bubbles look like. Lots of small bubbles constantly or intermittant larger bubbles? In addition, verify that the AC compressor clucth is engaged at idle.

The pressure switch mentioned can not be replaced "live", the system has to be discharged.

 

It's not just the airflow across condenser that makes a difference..

It's the higher rpms moving more refrigerant through the system.

 

I was looking at a lot of the vehicle titles of the people posting on the forum and they were 2nd gen owners. Also, I've been a member for less than a week, so still learning the ropes here. My 1st gen was similar in a lot of ways to the 2nd gen I own now and most AC systems are generally the same in most respects.

Yes, the AC clutch is engaged at idle. It's not blowing hot, just not adequately. I will check tomorrow and see if I can't find the pressure switch and report back. Thank you for the direction.

 

I get what you are saying, that just wasn't an issue with my truck until recently. It's always blown ice cold regardless, whether at idle or moving and I live in Mobile, AL. It's about to get super hot!

 

Its probably low on freon - slightly low or low enough to cause a noticeable drop in performance. The higher rpms mask the fact that its running on a less than full charge

 

I could see that being the case. Thank you for the input. I will definitely get it hooked up to a machine soon and find out if that is the issue. Honestly, that would have been the best place to start. It's an old truck, likely has a slow leak somewhere.

 

With most a/c performance concerns, checking refrigerant amount is almost always the first step

 

I know, I live in the south. Pretty much every AC shop has a line to China right now and I dont own gauges. These things never seem to happen at convenient times. My dad has an old machine and lives about 2hrs away. I'll probably head over there, see how much freon it pulls, fill it back and go from there. I did take the time to look for die traces, did not see anything under UV.

 

All of these belt driven ac compressors leak very slowly from the front shaft seal, and it allows the oil to keep the seal from burning up.
Your refrigerant will need to be filled up after a few years no matter what. It is not necessarily something that needs parts. If the compressor is cycling on and cooling you can fill the refigerant without evacuating the system.
Find the sight glass, clean it off and look for bubbles with the AC running; there will be no bubbles when the refrigerant is full.
This advice only applies to a system with no other problems.

Avoid using products that contain stop leak. It will gum up the system.

 

Love this advice! I appreciate it. You guys are awesome! I rebuilt the engine 3yrs ago, so that was the last time I had any dealings with the freon or AC system. Sounds to me like it i got my few years and it's time to top it off. I really need to find this sight gauge. I have no idea how I managed to miss it during the install.