Thoughts on my r134a pressure?

[JerseyJoe]

Guys, I sincerely appreciate your input, but this was my last try.
I vac'd it for over an hour today and was meticulous while charging it. It's just not building pressure before it cycles and I'm absolutely positive there are no leaks, I did not introduce air into the system while charging, and I have adequate airflow. I'm going to try and find somebody I can trust to work on it. I did everything on this car except assemble the trans, even did the paint myself. Something just isn't right and while I'm still "furloughed" I can't start throwing parts at it and hope it works.

 

[Demonic]

You are now undercharged, bouncing on the low side of the switch, below 30 psi.

 

[toddc72]

What happened to the system to need a new compressor? If it had a compressor failure? Also don't trust it saying had oil in it. I have seen a compressor come with almost nothing in it yet it claimed was ready to go. Was even warned by an a/c shop to check them also. Did you flush the system out and also inspect the orifice tube? Whenever I work on one. I evacuate it down. If all looks good than I put in 120 psi nitrogen into it to check for leaks. Vacuum will show some issues but system is under pressure when being used. So may seal fine with vacuum but leak with pressure. But also keep in mind outside air temp will have an effect on the readings to. Thinking it has a leak yet it really cold out. Would have to check it when the temp is about the same as you filled it at.

 

[JerseyJoe]

The plot thickens. The compressor was getting voltage fluctuating between 5v and 12v. I've been talking with Vintage and I'm going through it to get a steady 12v.

 

[Demonic]

? If the switch was interrupting power, of course it was. Your last vid shows suction pressure below 30 psi, where the switch opens. That then removes power from the compressor clutch.

 

[bearman]

? If the switch was interrupting power, of course it was. Your last vid shows suction pressure below 30 psi, where the switch opens. That then removes power from the compressor clutch.

I asked about the switches I think in the first post. Is it adjustable maybe if it is you can set it your cut out pressure.

 

[RJRENTON]

I asked about the switches I think in the first post. Is it adjustable maybe if it is you can set it your cut out pressure.

See my post #42 re pressure switches. They are mounted on a Schrader valve to allow for changing WITHOUT de-pressurizing the system. It is likely that IF switch is binary, it will have a minimum setting for low pressure protection AS WELL AS a normally closed, opens on high pressure setting to protect against excessive pressure. The access point, is inside the mounting stem. If the switch is responsible for the rapid clutch action, MAYBE the switch is damaged (internal contacts) due to the collapsing magnetic field? Just replace the switch....they are relatively inexpensive.
BOB RENTON

 

[dla4567]

See my post #42 re pressure switches. They are mounted on a Schrader valve to allow for changing WITHOUT de-pressurizing the system. It is likely that IF switch is binary, it will have a minimum setting for low pressure protection AS WELL AS a normally closed, opens on high pressure setting to protect against excessive pressure. The access point, is inside the mounting stem. If the switch is responsible for the rapid clutch action, MAYBE the switch is damaged (internal contacts) due to the collapsing magnetic field? Just replace the switch....they are relatively inexpensive.
BOB RENTON

That switch is NOT mounted on a schrader valve. Do not remove it without removing the refrigerant.

 

[1 Wild R/T]

That switch is NOT mounted on a schrader valve. Do not remove it without removing the refrigerant.

I agree.... Don't know where Bob R. is getting his info, very few switches are mounted over Schrader valves....

 

[RJRENTON]

I agree.... Don't know where Bob R. is getting his info, very few switches are mounted over Schrader valves....

Perhaps, I misspoke...
The valve shown in the summit link, screws into a fitting of sort, sealed by an O-ring. The switch I was looking at had a female threaded barrel that screwed over a Schrader valve type fitting. The low pressure cycling switch on my Denali fits over a Schrader valve type fitting and is removable without system discharge. I assumed, incorrectly, that the switch in the link was similar. Yes....the switch shown, will need the system discharged before removing.....I appologize for the misunderstanding.
BOB RENTON

 

[JerseyJoe]

Ok guys, its all wrapped up. Just addressing the last few questions, the safety switch is on the high side, low side pressures won't effect it directly. The compressor is fed voltage from the relay, the pressure safety switch just opens or closes depending on pressure to carry whatever voltage is getting to it, completing the circuit. I did not replace the compressor, this was the original kit I bought from them.
My compressor was cycling no matter what my refrigerant charge was, here's Vintage Air's explanation about the recommended pressure for their system:
Joe,
This is correct 6-20 LS and double the ambient temp +15-20% for the HS is what we recommend for the ideal cooling. The 50/275 value is the type of pressure you would find with an OEM system using an orifice tube and accumulator, with our systems we do not use an orifice tube or accumulator instead we use a expansion valve and drier on the liquid line. This will operate at a lower low side pressure than typically found in OEM systems, however the double ambient +15-20% is a universal standard that all AC guys should be using.
If you were to have 50 on the low side expect poor performance with our systems.

Tech support was awesome. Suspecting a connectivity problem after I put a test light on the relay and it was clicking like crazy so it looked like the issue was upstream. One test at a time, their tech sent me schematics highlighting exactly where to check voltage, resistance, or continuity.

And it led straight to my MSD unit sharing it's 12v supply with the evaporator/ECU and they were NOT playing well together... I wish I could blame someone else but I already said I did all the work
(66chargerpat was on to it early)
All is well, 16/200 psi and blowing 40°

 

[Demonic]

Oh thank goodness. 40 *F discharge air is awesome. Glad their tech says it's good.

Another fine example of the difficulty in remote diagnosis.

 

[JerseyJoe]

Oh thank goodness. 40 *F discharge air is awesome. Glad their tech says it's good.

Another fine example of the difficulty in remote diagnosis.

Hey, it made sense and I even learned something. Remembering is what I have trouble with!