Ac high side low pressure, but rebuilt ac system.

[JohnH55]

My explorer is an 2001 sport 4x4 256000 miles, and I rebuilt the AC systems. New compressor, condenser, accumulator, orifice tube, oring. The only old parts is the evaporator core, the lines and the low and high side pressure sensors. I flushed all the lines and evaporator core, then pulled vacuum and refilled the system, with 9oz pag46 and 30oz refrigerant, as per Ford spec. The low side at ~87 degrees, was 50 psi, the high side was 47 psi, the air got much colder on the highway, than at idle. I can't figure what is wrong, the only thing that comes to mind is that the high pressure shutoff switch, my be causing a problem. What is everyone else's opinion?

Thanks,
John

 

[1sicbronconut]

I've seen the same conditions when a orifice tube was missing could you have put it in backwards?? Is the compressor clutch engaging?

 

[410Fortune]

agree, although I am not sure you can install the tube backwards, it does sound like a plugged up tube

If the high pressure switch was the issue it would cut power to the compressor clutch, so as @1sicbronconut said is the compressor short cycling when this happens?

30oz of 134 and 9oz of oil?

with the two sides equal in pressure it seems like the compressor is not compressing, points to faulty compressor /leaks

Ac equal pressures info

 

[Gary Crist]

Sounds like reed valve failure in the compressor.
The system might have gotten a "liquid slug" oil or freon
or was just plain old bad from the word GO!

 

[JohnH55]

I've seen the same conditions when a orifice tube was missing could you have put it in backwards?? Is the compressor clutch engaging?

When I installed the o tube I followed a treads instructions, and installed it with the short side back. The clutch is engaging and stays on, no cycling. I don't think the compressor could be bad. It's a brand new 4 seasons, which I know is reliable.

 

[Gary Crist]

The bathtub of failure might just bite another one or,
"it can't be that part 'cause it is new"!
If you look at this pressure temp chart,
R-134a System Pressure Chart - AC Pro
It agrees with the temp you stated. If the oriface tube was
clogged (put in backwards) you would have a high high side and
high low side he freon can't go any where.

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[98EdBomber]

I agree usually when the pressures are the same the check valves in the compressor have gone bad. You could have just bought a DOA unit. It happens. Id look into returning it. At 87F you should see psi on low side 28-43 depending on humidity and high side 128-209 again depending on humidity.

Same pressure on both sides is classic symptom of check valve damage inside compressor.

 

[JohnH55]

I had a friend of mine ask his mechanic buddies, and they recommend replacing the switch, because if it is clogged then it will cause this problem. So i will do that then see what happens. If it still has low high side then a new compressor will be installed.

 

[98EdBomber]

See if its getting power and ground. If the clutch is spinning the switch works. Could it be clogged? Maybe...

You can also get weird readings if expansion valve gets stuck open/closed as well. But i think yours has orifice tube so its not that common unless you put it in backwards. Since its new its obviously not clogged.

Look up ratchets and wrenches on you tube. He has a great AC video that explains all this. Its in depth and very easy to understand and he gives examples of psi readings and why you get those readings.

Also found this one

 

[410Fortune]

It is quite possible the new orifice tube is now plugged with something, often with all new parts and flushing the lines and such I will find bits and pieces of material on the orifice tube...not a bad idea to check. Also the tube itself could be bad...not a bad idea to pull it and inspect since you did install new 4 seasons components....... whatever if happening it sounds like you need to collect your r134 and try again......

 

[410Fortune]

the high pressure switch is not likely to be your issue, since it does not have high pressure the switch is not cutting off the compressor = switch working!

 

[JohnH55]

the high pressure switch is not likely to be your issue, since it does not have high pressure the switch is not cutting off the compressor = switch working!

I'll have to open the system to replace the switch, 4th times the charm. Ill install a new motorcraft orifice tube at the same time, and see if it picked up some metal.

 

[Bjl8691]

What brands of parts did you use

 

[410Fortune]

It's a brand new 4 seasons

 

[fdbiii]

I'll have to open the system to replace the switch, 4th times the charm. Ill install a new motorcraft orifice tube at the same time, and see if it picked up some metal.

Don't waste time on the switch if the clutch appears to be engaged! As said before if the orifice tube was plugged the hi pressure would be very hi. You may have left the orifice out though!! Also check the key in the compressor shaft. It may have been left out especially if you bought an assembly and the clutch is spinning on the shaft. Check the compressor instructions. If it came with oil already in it (as some do) you have it oil logged and won't cool when you get the other problem fixed.

 

[koda2000]

If the compressor runs it's not the high pressure switch. It's running all the time because the compressor is not building enough pressure. I agree it sounds like a faulty compressor. Replace the compressor and while the system is apart check the orifice tube (you don't have an expansion valve). When the compressor is running and the low and high side pressure's are equal, that's a sign the compressor is not "compressing".

BTW - Bring your receipts with you showing that you flushed the system. Most compressor failures are caused by debris remaining in the system and if you can't prove you used flush they may blame the failure on you.

 

[410Fortune]

4 seasons compressors for these trucks come pre oiled

 

[JohnH55]

If the compressor runs it's not the high pressure switch. It's running all the time because the compressor is not building enough pressure. I agree it sounds like a faulty compressor. Replace the compressor and while the system is apart check the orifice tube (you don't have an expansion valve). When the compressor is running and the low and high side pressure's are equal, that's a sign the compressor is not "compressing".

BTW - Bring your receipts with you showing that you flushed the system. Most compressor failures are caused by debris remaining in the system and if you can't prove you used flush they may blame the failure on you.

Well I don't have the receipt for ac flush, O'Reilly's took it back when I returned the loaner tools. So I'm screwed there. And today the transmission went out. I think I'll just leave it as it is, and be done messing with it.