R12 TO R134 Conversion

[350runner]

Yes

 

[VAL]

Well, I finished up my conversion. I ended up flushing the evap, condenser, and hoses with mineral spirits then 2 quarts of AC Pro flush, pulled vacuum for 1 hour, New orifice tube, O-rings, new sealing washers for the hose ends on the compressor(which may I add, were a bitch to find), new accumulator, 3 12oz cans of the EZ chill with oil, 1 12oz can of synthetic arctic freeze R134a. This conversion worked like a charm, like 10 degrees colder that when it had r12. The temperature in my vents was at 46 degrees. I thought it was gonna get cool, but its way colder than my 2006 f150 by far.
When I first charged the system, my compressor started to kick on about 1 1/2 cans into it after the 4th can, it started cycling normally. My accumulator started sweating its ass off. After about 10min the cycling pattern changed, it was taking longer between cycles. Does anybody know what adjustment needs to be made to the pressure switch for the r134, if any?

 

[chengny]

When I first charged the system, my compressor started to kick on about 1 1/2 cans into it after the 4th can, it started cycling normally. My accumulator started sweating its ass off. After about 10min the cycling pattern changed, it was taking longer between cycles.

As the cabin cooled down, there was less heat available in the evap to boil off the SUVA. Consequently less refrigerant was able to pass through the expansion tube (then the evap coil and accumulator/suction line).

And, because of the reduced heat being transferred to the SUVA, the refrigerant that was able to enter the evap coil took longer to flash off. That increased the time required to raise the pressure in the suction line and close the contacts in the low side switch.

Textbook operation and performance.

One thing, the shell of the accumulator should sweat on a warm humid day. But keep an eye on it. Watch for signs of frost creeping up the pipe that comes out of the evap and connects to the coil.

If you can see frost outside the housing, it's a sure bet that your evap coil is frosted up. Frost in the evap and on the compressor suction/evap inlet piping is the first indication of a system that under-charged. Matter of fact, you might try to squeeze in another couple of ounces of straight refrigerant. That should raise the superheat temperature coming out of the evap and eliminate any heavy condensation or possibility of frosting up. That 80 - 90 percent number I gave you for 134a conversion is highly flexible. You might need a tiny bit more.

Just don't over charge the system. You'll lose track of where you are and end up dumping expensive SUVA just to get low enough to do a re-charge. It sounds like you pretty much nailed it on your first try.

The suction side of a 134a system on a hot day (with clean heat exchangers, cabin fan blowing max, no huge air leaks in the cabin and other variables not being an issue) should run about 33 psi. I think those switches come set to close at 35 psi and open at 30 psi.

If you want to play with the set point, it is adjusted by that screw between the two blades for plugging in the harness.

 

[VAL]

When I first charged the system, my compressor started to kick on about 1 1/2 cans into it after the 4th can, it started cycling normally. My accumulator started sweating its ass off. After about 10min the cycling pattern changed, it was taking longer between cycles.

As the cabin cooled down, there was less heat available in the evap to boil off the SUVA. Consequently less refrigerant was able to pass through the expansion tube (then the evap coil and accumulator/suction line).

And, because of the reduced heat being transferred to the SUVA, the refrigerant that was able to enter the evap coil took longer to flash off. That increased the time required to raise the pressure in the suction line and close the contacts in the low side switch.

Textbook operation and performance.

One thing, the shell of the accumulator should sweat on a warm humid day. But keep an eye on it. Watch for signs of frost creeping up the pipe that comes out of the evap and connects to the coil.

If you can see frost outside the housing, it's a sure bet that your evap coil is frosted up. Frost in the evap and on the compressor suction/evap inlet piping is the first indication of a system that under-charged. Matter of fact, you might try to squeeze in another couple of ounces of straight refrigerant. That should raise the superheat temperature coming out of the evap and eliminate any heavy condensation or possibility of frosting up. That 80 - 90 percent number I gave you for 134a conversion is highly flexible. You might need a tiny bit more.

Just don't over charge the system. You'll lose track of where you are and end up dumping expensive SUVA just to get low enough to do a re-charge. It sounds like you pretty much nailed it on your first try.

The suction side of a 134a system on a hot day (with clean heat exchangers, cabin fan blowing max, no huge air leaks in the cabin and other variables not being an issue) should run about 33 psi. I think those switches come set to close at 35 psi and open at 30 psi.

If you want to play with the set point, it is adjusted by that screw between the two blades for plugging in the harness.

Today I put the gauges back on the truck, everything is running normally. The cycling is different today. I have been doing some reading on it, and it seems that ambient temperature & humidity play a role on how the system works.
I currently have 42oz of R134a, 6oz of oil, according to the calculations, I'm a about half a can of r134a short of being full charged, maybe I should just leave it at that, because the a/c is extremely cold. The temperature in the vents went down to 41 degrees this morning, WOW! It gets really cold in that small cab.
I want to thank you Chengny and everyone else that chimed in, for all your help. The info you provided was outstanding and invaluable to a DIY'er. You basically walked me through the whole process step by step.

Thank you my friend.

 

[flyboy1100]

I need to do this. I don't have voltage going to my compressor and I suspect it is because I either have no r12 or not enough

Sent from my SCH-I605 using Tapatalk

 

[VAL]

I need to do this. I don't have voltage going to my compressor and I suspect it is because I either have no r12 or not enough

Sent from my SCH-I605 using Tapatalk

I had my a/c redone a few years ago with the original R12 refrigerant. It worked good for a couple years, until it developed a leak somewhere, and I lost my R12 pressure, compressor wouldn't kick on, warm air through the vents etc. When I went to the shop to have it diagnosed, they told me I need to recharge the system, and a 12oz can of r12 was $65 a pop, and I needed 5 cans. I then inquired about having the system converted to R134a. The shop said I would need to swap out all the major components, and they estimated the cost to be somewhere around $1300.00, screw that! I did the conversion myself for under $300(and that's including the gauge set I bought). I'm glad I decided to convert it myself. The R134a conversion seems to cool much better than the r12. I learned a great deal about a/c systems, I know everything was done right, and I have a sense of accomplishment.

 

[flyboy1100]

What was the leak? Mine could have just lost enough due to age too

Sent from my SCH-I605 using Tapatalk

 

[VAL]

Where the hoses connect to the compressor, there's 2 sealing washers, they were shot.
Also, when I put everything back together after the flush, when I was pulling vacuum, the new pressure switch was leaking. I come to find that the pressure switch seals better if you just hand tighten it. I had put a wrench to it and over tightened it, and it wouldn't hold vacuum until I loosened it, then hand tightened it down. It sealed beautifully by hand.

 

[flyboy1100]

Thanks
How did you pull vacuum?

Sent from my SCH-I605 using Tapatalk

 

[VAL]

Thanks
How did you pull vacuum?

Sent from my SCH-I605 using Tapatalk

I rented a 2.0 cfm vacuum pump from Autozone, hooked it up to my manifold gauge set, opened up the valves, let it run for a little over an hour. They also had(rented me) the flush canister, you have to hook it up to an air compressor, and buy the solvent. It was like $130 for the rental, got it all back after I returned it. Worked great.

 

[flyboy1100]

Thanks

Sent from my SCH-I605 using Tapatalk

 

[MrMarty51]

Another question ?
I charged the system on My 93 K1500, after the conversion and total flushing, along with new hoses.
I do not remember what the readings of the gauges was.
The compressor just ran, without cycling. The temp. was about 97*F that day. I do`nt remember if I had tried the fan on low so, I do`nt know if the compressor was then cycling off and on.
A cooler day, the temp was in the mid to high sixties, fan on low, the compressor was and still is cycling when the fan speed is on low, set the fan to mid, or, high and the compressor runs constantly.
When the fan is on low, the compressor will run for quite a while then, kick off for about a 1/2 to one minute then, it will run for a long time again then click off.
Is this normal operation or, am I a bit low on freon ?
At the time I did the recharge, the lowest I could get the system to cool to was about 51*F.
Might it be an over-charge ? ? ?

 

[VAL]

The pressure switch will cut power to the compressor at a different points, depending on charge, ambient temperature and humidity factors. When I first started to charge my system, the compressor kicked on after about 1 1/2 cans into it, then cut out. After the second can is kicked in for a little longer period then off again. after the 3rd can it stayed on and started to cycle normally. On really hot days, don't expect too much cycling. I currently have 4 12oz cans of r134 which is a total of 42oz of R134 in it, and the cycling varies. during normal cycling, my compressor will kick off when the low side pressure reaches a certain point, but it doesn't kick off for no more than 5-10 seconds at a time. My guess would be that your low on refrigerant, or you have a bad low pressure switch. On your 93, the amount of refrigerant might be different, check the sticker in the bay area somewhere or your manual to get that info. Chengny can chime in on that, and help you out.

 

[MrMarty51]

Thank You very much, that helps a lot.
Now I know that it is normal for the compressor to cycle.

 

[chengny]

Chengny can chime in on that, and help you out.

My work here is done, VAL. I have taught you all I know.

It's time to step aside and pass the torch to the next generation.