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Roamer37 · 06-24-2022, 09:12 AM

Quote:

Originally Posted by Tha_Rooster

Just a thought tech vacuum out 3 lbs after it had been leaking enough to turn off compressor? So how does tech know that 3.5 is enough?

He fixed the leaking hose fitting, vacuumed out the system and refilled it with 3 lbs. The system capacity is 3.5 lbs. so this morning he vacuumed it out again and put 3.5 lbs. Alas it still won't run. So the dash will most likely have to be partially removed to get to the pressure switch. That seems most likely to be the culprit. At least the leak is fixed and it's holding pressure. It's never easy.

Roamer37 · 06-26-2022, 05:51 PM

So if I replace the low/high pressure switch does that cause the refrigerant to lose pressure?

Tha_Rooster · 06-26-2022, 06:22 PM

Quote:

Originally Posted by Roamer37

So if I replace the low/high pressure switch does that cause the refrigerant to lose pressure?

Yes, have you jumped it?

Roamer37 · 06-26-2022, 07:03 PM

Quote:

Originally Posted by Tha_Rooster

Yes, have you jumped it?

Not yet. Debating if I want to open up the dash and jump it or just live with it for now and run the genny and roof air.

GWCowgill · 06-29-2022, 02:40 AM

Quote:

Originally Posted by Roamer37

We have our 1999 Discovery 37V at a truck shop for AC work. The dash AC gradually stopped working last year. I found an AC hose fitting that was leaking. They put a new o-ring in it and charged the system. The compressor will not turn on. They ran power to the compressor directly and it started up and blew cold air. He said the pressure on the high side was 375 and the compressor needs 300 to run. They cannot figure out why it won't start up.

Does anyone have any suggestions on this? Thanks!

I believe you have an in-line low pressure and high pressure switch. If all other electrical is good such as fuses then I would suspect the low pressure switch. Have the mechanic bypass the low pressure switch and see if it then runs from the dash. 375 pounds static sounds high.

Jdavidlanier · 06-30-2022, 05:22 PM

Automotive a/c systems with r134a usually have a high pressure switch that cuts out compressor if high side pressure is over 350 psi. That is standard for these systems. On a 90 degree plus day, running a/c on high fan speed, pressures can reach 325 psi easily. But engine cooling fan should keep it below that.
Recommend ensuring proper amount of r134a is in system; too much can cause too high pressure! Bypassing, and straight wiring compressor will turn it on, granted, but it can cause a/c lines to leak-even blow out if there is too much refrigerant! That being said, yes there are fuses and relays in the system that can fail. But my suspicion is too much r134a by your comments. Hope this helps! Safe and blessed travels!
One other item I forgot to mention, is the system may have an orifice tube as an expansion valve; if it is plugged, it also can cause too high pressure! If so, you might want them to check for accumulator desiccant failure.

retired long · 06-30-2022, 06:11 PM

Quote:

Originally Posted by Roamer37

We have our 1999 Discovery 37V at a truck shop for AC work. The dash AC gradually stopped working last year. I found an AC hose fitting that was leaking. They put a new o-ring in it and charged the system. The compressor will not turn on. They ran power to the compressor directly and it started up and blew cold air. He said the pressure on the high side was 375 and the compressor needs 300 to run. They cannot figure out why it won't start up.

Does anyone have any suggestions on this? Thanks!

80 degree outside temperature with low an high pressure gages connected system should show40-50 psi on low side175-210 psi on high side. That is with compressor running.I dont know where tech is getting 375psi but that would only be pressure with compressor running an outside temperature 110 degrees! I dont know the outside temperature you are dealing with but that is from chart your tech should have access too.
Only proper way to fill system is with acurate gages connected to low side an high side of freon lines. --now outside temperature an compresssor must be running.Again i dont know where yo u are getting 375 psi if compressor is not running. Be adware any good system will have a low pressure safety switch will stop compressor if low in freon an also will have a safety cut off switch that will not allow compressor to run an perhaps damage system.

donr103 · 06-30-2022, 09:35 PM

You could have stuck or plugged up expansion valve.. many of them have a filter screen inside them.. but.. and here is big but.. you usually have to remove part of dash and take out evap box..
Good luck and keep us posted

richardkronz · 07-01-2022, 04:00 AM

Quote:

Originally Posted by Tha_Rooster

If you have a low pressure cut out switch have you straight wired it to see if compressor kicks on?

Thats the first thing I thought of. The high side switch cuts out on too high pressure, which you wont get with a non- operating compressor. The low side switch cuts out on low pressure, so thats where I would look first.

THenne1713 · 07-01-2022, 08:35 AM

Overcharged, or one of dual electric radiator/condenser FANS has failed or dragging/ running slow? SOMETIME, ANSWERS RIGHT IN FRONT OF US GET OVERLOOKED. It will not get to 375 unless compressor has run? Good Luck, ask for another Tech?

Roamer37 · 07-01-2022, 02:55 PM

To clarify, it’s not 375 static. When he wired the compressor direct it ran and blew cold. That’s when the pressure was 375. It’s my understanding that when run direct like that the pressure will be high because the condenser isn’t running.

My coach has a binary high/low pressure switch. I haven’t tried jumping it yet because it’s buried in the dash. There’s a couple relays in there too that the Discovery guys suggested changing out. So I’m debating if I want to take the dash apart or not. They say it’s not that bad lol.

retired long · 07-02-2022, 09:03 AM

I will repeat. If the tech does not have gages (high an low pressure ) connected an know ambient temperature an have a printed chart telling him the proper presssure both low an high should be he is shooting in the wind.You mentioned he said 300psi is needed for compressor to run. You sure he didnt say 30psi.300psi is totally wrong.If he has gagues connected an we knew the low an high pressure it would help us an also the ambient temperature while he is working on it.