Motorhome R134 Problems

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philipswanson
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Joined: Fri Jan 04, 2019 9:32 am

Re: Motorhome R134 Problems

Postby philipswanson » Tue May 19, 2020 2:32 pm

Static pressures are: 85 on the low side and 100 on the high side. Ambient is 70 degrees. Does that tell me anything?
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bohica2xo
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Re: Motorhome R134 Problems

Postby bohica2xo » Tue May 19, 2020 4:43 pm

None of your number add up.

First post you claim 110 psi on the high side, 25 to 30 on the low side. Cycling. With an Ambient of 60 F. and only 55f from the vents.

Then you post that the system is 25 to 28 on the low side, high side 100 - and the compressor is stopped.

Then you added 20 ounces of refrigerant - and saw 280 to 300 psi on the high side. IF that was at your 60F ambient you are way overcharged.

The static pressure for 134a is pretty close to the refrigerant's temperature. At 60F it is 57.5 psig. At 65F it is 64 psig. P/T charts are all over the internet.

So either you have a gauge problem, a coupler problem or a switch problem.

Hard to say with incomplete test data. In the future Low Side, High Side, Ambient Temperature in front of the condenser, Vent temperature and RPM Without all of that data at the time of test, the information is of no value.
philipswanson
Posts: 37
Joined: Fri Jan 04, 2019 9:32 am

Re: Motorhome R134 Problems

Postby philipswanson » Tue May 19, 2020 5:57 pm

RPM is 2160 as I mentioned before. Ambient is 60-70 degrees. The high pressure shots up periodically to 200+ but only as the compressor cycles. The clutch only stays engaged for 10-15 seconds, then the high side drops back to 100. What test data are you missing? I am going to shut down the condensor fans (3 that run full time) because I read if you are pulling too much heat from your condensor, it will not build enough pressure.
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bohica2xo
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Re: Motorhome R134 Problems

Postby bohica2xo » Wed May 20, 2020 1:05 pm

Ok, so now the high side is 200+ when the pump is running - not 110. At 70F ambient a condenser with good airflow should be under 200 psi on the high side.

Just how big is this condenser? And how big is the evaporator?
philipswanson
Posts: 37
Joined: Fri Jan 04, 2019 9:32 am

Re: Motorhome R134 Problems

Postby philipswanson » Thu May 21, 2020 2:07 pm

I called Jeff over at Transair who is their Tech Rep. He knew the problem and solution right away. The thermostat. He had me jump it and sure enough, the compressor came to life and cycles just as it should. Cold air too all of a sudden. I appreciate the help but it pays to call a Tech Rep who knows the system. It sure is better than spending hundreds or even thousands replacing parts and doing labor with no success. Especially when its something so simple. Didn't even need a jumper, just moved the spade terminal directly to the switch, permanently bypassing the thermostat. A thermostat does absolutely nothing in a large motorhome anyway. Now its either full on or off, just the way I want it.
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bohica2xo
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Re: Motorhome R134 Problems

Postby bohica2xo » Thu May 21, 2020 5:13 pm

Just like I said before:

"A Switch Problem"

When I asked if there was a thermostat involved you answered that it cycled on pressure switches.

So by providing useless information in post after post you never got a solution.

320 psi @ 70f is still overcharged.

Good luck.
philipswanson
Posts: 37
Joined: Fri Jan 04, 2019 9:32 am

Re: Motorhome R134 Problems

Postby philipswanson » Fri May 22, 2020 3:16 pm

It does cycle on pressure switches as well as the thermostat. That's what they do. Funny how a tech rep sees it right away. Sorry I didn't answer exactly correct. That happens, I am not a professional but that's what it took to solve the problem.

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