For those that have converted from R12 to R134a, what did you do?

1. Nothing, just recharge with 134a?
2. Change oil,
3. Drier
4. expansion valve
5. Hoses
6. Low pressure switch

Also, on a typical 90+ day, what are you running for high pressure?
I suspect the early dakota's would run a higher head pressure when setting due to no electric fan.

Look forward to hearing from others.

 

Everything; but then, I was also fixing a bad heater core and replacing the radiator with an Extreme Cooling Option radiator; so it made sense to do it all.

Drain; change oil (if recycling compressor, evaporator, condensor, and hoses, use ester, not PAG; if all new, use PAG); replace drier, expansion valve, and charge is the lowest I'd go. the LPS needs to be swapped to a R134a switch (due to the differing pressures), but you can avoid that for now. The hoses may, or may not, work with R134a; R134a is a smaller molecule, and not all hoses from the late 80's are dual-barrier hoses (i.e., nothing wrong with hoses, but R134a will still migrate out of them due to them being slightly porous at the size of the R134a molecules). Expansion valve and receiver/dryer because it's open.

And evaporator/condensor for, well, the reasons I stated above.

You may want to consider a new compressor also; R134a tends to build higher pressures on converted systems, and the compressor may just be old and tired enough to fragment under the increased load. (Yes, I did also, but that was due to wanting to be thorough about it.)

Head pressure - Well, that's a conundrum. I've been having problems getting a full charge in; at 95F ambient right now I'm at 170lb high / 25lb low (!!!) Also, my sight gauge on the receiver/dryer shows white foam; with R134a, I should get it down to a stream of bubbles (R12 you get rid of the bubbles; R134a not quite as much charge, so some bubbles will remain.) And as you may guess, it's not ice cold at all. It STILL beats 95F with a HI of 107/110F windows down, so there's that.

I'll post again after my next try to charge a bit more.

RwP

 

Hey Ralph, thanks for the reply!! FWIW I am a HVAC contractor, and most of what you said, I knew. Judging by your pressures, I am overcharged. I should recover the r134a and weigh the charge back in. My compressor is getting noisy and its not cooling as well as it used too. Something that threw me off was the expansion valve (metering device) is the same for R12 and R134a.
Again, FWIW according to rock auto, the 87 used the same expansion valve as a 95-99 neon. But the 93 dakota is different. It appears it would interchange, but the superheat setting is 7.5 vs 10 on the 87 valve. Not sure why they did that in 93 but went back to the older style in 95.

 

Yours may not be overcharged; I KNOW mine is UNDERCHARGED.

Since your R/D has the sight gauge, I'd use that to verify charge. Note: Most R/D manufacturers paint over it; I had to scrape the paint off.

You probably know more than I do on the relative number of bubbles through the sight gauge if you're in the business; I just read, study, and adsorb information from others *grins*

RwP

 

Quote:

Originally Posted by RalphP

Yours may not be overcharged; I KNOW mine is UNDERCHARGED.

Since your R/D has the sight gauge, I'd use that to verify charge. Note: Most R/D manufacturers paint over it; I had to scrape the paint off.

You probably know more than I do on the relative number of bubbles through the sight gauge if you're in the business; I just read, study, and adsorb information from others *grins*

RwP

Backing up on this story some,

About 5 years ago, my brother gave me this truck. It was out of freon. So I pulled a quick vac. on it and charged it with 134a. It would last about 3 months and have to be topped off.
My plans have always been to put a V8 magnum in the truck, so that said, didnt spend anymore on the ac then I had too.
Well the leak got bigger, and soon it was every 2 weeks, recharge. Found the condenser leaking.
Picked up a new condenser off of ebay for a real low price. $40.00 added a few ounces of mineral oil and recharged with the 134a.
Well still it has to be topped off every year or so.
I believe the leaks are in the hoses.
On the times its been down, ie, condenser replacement, I weighed in the charge.
Ashamed to say, never had a high pressure guage on it until the other day.
The day was 90+ and with a fast idle, (1,000 rpm's?) The low pressure would come on at about 40psi, and slowly drop, (30-45 sec. ?) to 17-20psi, and then cut out. But head would climb to 280-285 psi.
This morning, outdoor temp is 76. Compressor stays on much longer, and finally dropped out at 19psi. Head never went over 180psi.

I think I am going to leave it alone for now, But I suspect an electric fan conversion would help a lot!!

Again FWIW my hvac knowledge is mainly residential. I looked in to converting my 93 corvette to 134a, but decided against it and kept it r12. Its never had a problem, so why mess with it.
But on a GM conversion, usually you put a different orfice tube in to match the 134a. I was surprised that dodge used the same metering device (expansion valve) for both refrigerants.
When I do the V8 magnum, it will be a serpentine belt compressor, it appears to use different connections and it will be further forward. So at that time, I will probably go with a new or rebuilt compressor, lines, etc, and flush everything out.

Ralph, again, thanks for your help!! I always learn something from your post!!