westside807

I have a 71culass. It has factory air. I changed the compressor and the drier to r134a. I replaced to POA valve with the bypass. The condenser and evaporator weren't replaced. The hoses/pipes under the hood get real cold and condensate, but the air in the cabin get only cool, never cold. The air out of the vents never seem to match or come close to the feel of the hoses under the hood. The system works, but it just doesn't get as cold inside the cabin. I don't know the vent temperature. The low side pressure while running is around 44psi. That psi seems to satisfy the poa bypass and keeps it from cycling off at higher rpm. I don't know the high side psi. Any ideas on what I can do to make the vents blow colder? Or am I missing something?? Thanks!

oldcutlass

Get one of these and see what your vent temps are.

westside807

Ok

Fun71

Definitely need to check the vent temps.

44 psi for R134A in a system with an R12 evaporator seems high to me. Most folks who do the R134A conversion adjust it so the low side is a bit lower than it was with R12 (which should be low 30s, depending upon the ambient temperature) in order to achieve the same vent temps as with R12.

westside807

Ok, the thermometer says 60 degrees straight up. The instructions for the thermometer say temps from the vents should be between 45 and 60 degrees. Its 94 degrees right now outside.

westside807

Just to compare, my wifes 2007 was somewhere between 40 and 50 degrees. I know that it won't be the same but is my system at 60 degrees coming from the ventsrunning up to its full potential? Is this all or the best I have to look forward to? Or is there ways to lower the vent temperature?

Fun71

In order to get the vent temps comparable to an R12 system, you will need to adjust whatever is controlling the low pressure cutoff. I don't fully understand when you sou said you "replaced the POA with the bypass" but this "bypass" thingamajiggy is what you would need to adjust in order to decrease the low pressure cutoff and drop the vent temps.

This is assuming that you have the proper amount of refrigerant installed and the pressure you posted is correct for the ambient temp.

FYI my 1998 Jeep Wrangler's R134A system has right at 40º vent temps when it's 110º outside, but that is with a system designed for R134A.

westside807

My poa valve was clogged so I bought a poa eliminator kit

gs72

When converting to r134 you have to figure out what 85% of the r12 capacity of the system is. Then charge it with that amount of r134. Sometimes you have to play around with it, pull out a half ounce to an ounce or vice versa to get the best efficiency.

Fun71

Agreed, that is what I meant by ensuring the proper amount of refrigerant installed.


The picture shows a low pressure cycling switch, so you should be able to adjust the low pressure trip point. From what I remember about those switches on factory R12 systems, there is a screw on the switch, under the electrical plug, that can be turned to adjust the low side pressure. What I remember reading about converting from R12 to R134A, the R12 systems had ~32 psi trip point and decreasing it to ~28 psi would drop the evaporator temps so they were comparable to the R12 temps.

I just had a thought - since this is a retrofit for an R12 POA valve, it is possible that the low pressure trip point is already set lower than it would be for a system completely designed for R134A. I would suggest contacting the seller and asking them.

Fun71

OK, I just searched for "POA Eliminator Kit" and found an installation document from Original Air:

http://www.originalair.com/downloads...2%2015-403.pdf

From the instructions:

The screw must be turned APPROXIMATELY 3/4 of a turn COUNTER CLOCK-
WISE. This will bring the cycle-off pressure down to 21 psi, which is needed
for R134a.

Since you said the low side pressure is 44 psi you apparently have not performed this adjustment, or the system is overcharged with too much refrigerant.

westside807

This evening I checked my low side pressure it started at 44psi and the vent temp was 59/60, then for some reason that I don't know the gauge went down to 30 psi. The vent temp was about 46 degrees. Outside temperature was 85 degrees. So 2 things 1. I have a leak maybe
2. It cooled better at the lower psi, but it was cooler outside too

Fun71

That system is designed to cycle the compressor on and off to keep the evaporator just above the temperature where it would freeze up. During normal operation, the compressor should run for a while then cycle off for a shorter while (this will vary with ambient temps - at really high temps it may run continuously). This all assumes there is sufficient air flow across the condenser to remove heat from the system and the engine is above idle speed (R134A systems don't cool as well as R12 does at idle). Oh yeah, and the correct amount of refrigerant.

westside807

It should be 98 degrees today I'll see what happens and check the readings. The 46 degrees was great last night. If I can get that all the time that would be perfect!

banny

Another possible thing to check is inside the evap housing as debris tend to accumulate over many yrs. That can really affect the performance of the system. Just a couple of the many ive come across.

westside807

Yesterday in 92+ degrees my low side was reading 44psi and the vent temp was 60/58. I then started releasing some of the pressure. I stopped around 35 psi because my vent temp was about 48 degrees. So my system seems to blow coldest around 30-35psi. I considered lowering it to 30 but stopped at 35, I'm not sure what's too low.

banny

You can go down to 30 psi for r12 and even further down to 26 for 134a

westside807

Thanks banny that's good to know. I was told to put 42-45 psi initially. Those numbers worked for that gentleman's application but I'm learning that each application is different, seemingly. I may go down to 30 since I could go as low as 26. But I'm not sure if it will do any better than 48 degrees from the vent.

Fun71

The info I posted earlier said it needs to be adjusted to 21 psi low side pressure for R134A operation.

westside807

Wow , thanks fun71! I didn't see that post for whatever reason.

westside807

I just looked at the attachment and it says at 21 psi the system cycles off the clutch. I'm not sure that means i should reduce the pressure to 21 psi.

banny

You actually set the psi as low as 20 if you wanted to. Classic Auto Air sets their poa valves to 20 psi for 134a

westside807

Maybe I'm misunderstanding. Setting a POA valve to cycle off at 20-21 psi is different from what psi the gauge is reading in with the system just on and running before it cycles off, right??