I have a 96 E-350 7.3 PSD. I noticed that the A/C seems to work well on the Highway but not so well stopped Idling. I thought maybe it was airflow so I replaced the Fan Clutch... Seemed like it was better for while (could have been my imagination)... I decided to evac the system and refill. The system takes 4 lbs of freon. The van was indeed low so I thought I had found my problem, but it didn't seem to help after evacing and refilling.

With gauges on the system the low side pressure when it was 80 degrees out this morning was 70 and the high side was 145. A/c temp from the vents was about 70.. If I raised the RPM's to about 2k, the low side would drop to around 30-35 the high side would stay about the same... and the AC in the Cabin was in the 50's...

Does this problem have to do with air flow over the condenser, or is possible that the compressor is getting tired. (The compressor stays on the entire time) Could it be a clogged orifice?

Any thoughts would be appreciated

 

This was my first post. Did I miss something or post this in the wrong area. I would think somebody has dealt with this... I have read similar issues from the archives... How did anybody resolve. I am going to try changing the fan clutch again... perhaps i received a defective one.

Any comments appreciated.

 

The gauge readings you posted seem a bit wonky. Need a little more info.

4lbs of R134a? Obviously, it has Rear AC. Is it a factory Dual system or is it a Conversion van?

At 80*, 145 on the High Side is pretty low.
70psi on the Low side at idle is really strange, but 30-35 at 2K RPM is just about right on a single system. Dual systems usually run a bit higher.

Did you have both hand wheels on the manifold gauge set closed when you took the readings?
Are you sure the system took in all 4lbs of refrigerant? Did you pull a hard vacuum with a vacuum pump before charging? (Just making sure of your terminology).

Your original symptoms are classic for poor condenser airflow, but the pressure readings don't bear that out. The little voice in the back of my head is saying there could be an issue with the rear expansion valve. Like stuck mostly open.

Look at the AC lines under the truck. Many vans destined for conversion had "upfitter" ports with shutoff valves under the driver seat area. I can't say if the vans with factory AC had them. You could close the valves and isolate the rear system out of the equation that way.

Hope this helps, even a little bit.

 

 

It would appear that the compressor isn't compressing properly.

 

Might be as simple as the clutch is slipping. East to fix but who knows if you'll be that lucky.

 

Thanks for everybodies inputs... I am not familiar with all the lingo of car mechanics but i will do my best, i'm not afraid to get my hands dirty and have rebuild a chevy truck a/c system before so I learned a bit with it.

back to LSRX101

I will Put the gauges on again later either today or tomorrow. 4lbs of R134a is correct, it has Rear AC and is a factory Dual system.


Did you have both hand heels on the manifold gauge set closed when you took the readings? Yes, ( I will double check when I run it again)

Are you sure the system took in all 4lbs of refrigerant? Yes...

Did you pull a hard vacuum with a vacuum pump before charging? vaccumed for about 10 -20 min. (maybe should have a bit longer?)

Your original symptoms are classic for poor condenser airflow, but the pressure readings don't bear that out. The little voice in the back of my head is saying there could be an issue with the rear expansion valve. Like stuck mostly open. (I have tried running the system with the rear off and it doesn't seem to make a difference) They both begin to be cold on the highway. I have a replacement clutch I am going to put in.

I watched the condensor run, and the center of it is rotating constantly when the A/C is on I assume this means the clutch is working?

Thanks again for everybodies ideas... I'll keep posting my progress or lack thereof.

 

The condenser is in front of the radiator. It doesn't run anywhere. You were looking at the clutch hub on the front of the compressor.

Let's get new pressure readings.

 

Ha yes indeed sorry the Condensor does not run anywhere, as I did mean to say the Compressor. (guess I should re-read what I type) I Will try and take readings tonight.

 

Ok, I finally got around to putting the gauges on again. This is what I found.

Outside temp around 110 degrees.

With engine off both High and Low side were around 115.

Engine Idiling Low side was around 94 and High side around 220

With the idle up probably around 1.5 to 2k rpms.. the low side was 56 and the high side was about 245.

Anybody have any idea how to interperate this?

 

Insufficient differential is usually a weak compressor or a slipping clutch. However, an overcharged system or a stuck open rear valve as mentions will give similar readings.

 

Is there anyway to know if it is a weak compressor without replacing it?

 

Block the airflow over the condenser. The high side pressure should climb pretty quickly. If it gets up to 350-375 or so, the compressor is ok. Don't let it go much higher than that.

Did you look for the shutoff valves in the rear lines? If it has them, you can close both of them and isolate the front section for testing. That would confirm or rule out a bad rear TXV.

 

Great Ideas, I will try them... I have not looked for the rear shutoff valves, I did not realize that a factory system would have them. I will check next chance i get.

Thanks again.

 

I mentioned the shutoff valves early on in this thread. It got pretty busy with replies, though. No biggie.
Look underneath the van, around the driver seat area.
Vans destined for conversion and cutaway units all had them if equipped with AC. I don't know if vans with Factory AC had them, though, I never noticed.

Keep us posted on what you find.