I should of come here first! I got some bad advice and tried to convert my 87 F250 from R-12 to 134a without properly flushing the system. It blew cold for about 30 sec then went hot.
I was doing this after being told( by the same friend) that you couldn't get r-12 anymore here in California, and that there probably wasn't any r-12 left in my system since it hadn't worked in over a year. I did do the compressor checks and knew it was working.
So at this point have I totally screwed up my compressor and/or any other part of the system? Can I just do the flushing and replace the necessary components to do this properly?
One local shop said no one here would or could evacuate a mixed r-12/134a system, because they use two different machines for each type.
Thanks,
Mike

 

are you sure the compressor is turning? maybe the high-pres. cutoff switch is bad.. try unplugging it, and using a jumper wire on the plug to see if the switch is working or not..if the compressor comes on, then your cut-off switch is at fault. i had that problem on my F250...

 

Thanks. Yes, I did bypass the pressure switch and the compressor comes on.
I'm just trying to find out if running the mix of 12 /134a for even a short time has possibly damaged anything. I've been reading the flushing proceedure and will delve into that after gleaning any additional advice here.
Mike

 

Did you pull a vacuum before you installed the R134? My '83 is running R134 and it runs just fine. Havent had to mess with it in over 3 years.

Also, did you add a can of refrigerant oil?

 

No, I didn't pull a vacuum, nor did I add a can of oil. I now know what I should have done and will do it right this time. I had a vacuum pump but couldn't get it to work properly. Impatience,lack of money and ignorance all came into play here.
Mike

 

if there was a good amount of R12 left in there then you might have a problem.. how many cans of 134A did it take? if it was totally empty it should've taken 2 and 1/4..

 

I put in 3 cans I think. Sounds like I have too much? I know there are other issues like the r12 oil not being compatable with 134a.
Thanks, Mike

 

OK Vacuum it down and leave it alone for a little while. Let as much of the old freon boil out of things like the receiver/dryer, etc so there wont be anything to mix with the new charge. Doing this also removes moisture which is a big no-no with air conditioning.

After you are sure you dont have a leak... the vacuum gauge does not move at all, put in the can of oil first. Then, put in a can of 134. Start it up, blower on high, running on recirculate, and add the 2nd can. You should be using a gauge for this, too. DO NOT add more freon than what it takes to get the gauge to read in the 'normal' area. Overfilling will really increase pressures, and possibly blow a seal, or, a line. Remember, 134 operates at a higher pressure than R-12 did.

You MUST always pull a vacuum. I dont care what guys say. You cant have any old freon, or air of any kind in the system.

 

Thanks Holmes,
I'll try to get on it today. I'm out in Butte County ,N Cal where all the fires are and its like smokey grey hell outside right now.
Mike

 

There is no High Pressure Cutout switch on your truck. The switch on the accumulator is the Low Pressure Cycling Switch.

You don't mention if the compressor engages. It sounds like it isn't and bypassing the cycling switch lets it engage. Either the switch has failed or there is no refrigerant left in the system due to a large leak.

To do this properly, you need a vacuum pump and a real manifold gauge set.
- Evacuate the mixed refrigerant
-Drain the compressor and "flush" it with BVA 100 Ester oil then add about 2-3 ounces.
-Disconnect all of the lines, remove the accumulator and orifice tube and flush everything with solvent and blow it dry completely on the inside,
-Reinstall all of the parts using new, lubricated o-rings on all of the connections, a new orifice and new accumulator. Spread about 6-7 more ounces of oil among the other components.
-Replace the cycling switch. Turn the adjustment screw in the connector end 1 turn counterclockwise. (Little known trick for R134a conversions).
-Pull a vacuum for about an hour.
-Charge with R-134a to about 80% of the R12 charge amount. Tweak the amount 1oz at a time as needed.

One other thing that really should be done is to replace the fan clutch. Although they move enough air to cool the motor, an old clutch won't move enough air over the condenser at idle. This will cause the AC performance to be weak at idle and can damage the compressor. there is no way to accurately test an old fan clutch .

Good Luck

 

Thanks ISRX, Do I have to unbolt the condenser to properly flush it?
The compressor was cycling until I started this. Now it only cycles with the low pressure switch bypassed.
I'll let you all know how things come out. It was 110F here yesterday,with smoke so thick you could only see 100 yards.
Mike

 

Yes, you will need to remove the compressor. Hold it with the ports facing downward and turn the shaft to pump out the oil. Add a few ounces of fresh oil, turn the clutch about 10 times in the proper direction then drain it again. Add more oil and repeat. Add and repeat one more time draining thoroughly. (3 fill and drain cycles). Finally, add about 2-3 ounces while turning the clutch to draw it in.

If there is less than 45 psi (static pressure) in the system, you have a leak. If there is more than 45psi the switch has failed. You need to know the pressure to be sure. It's possible that, with big overcharge, you popped a hole in a line or other component somewhere. Look close at the inlet and outlet tubes on the condenser, they tend to rust through in my neck of the woods.

Good Luck, with the AC and the Fire/Smoke. Don't let the flames sneak up on you.

 

Isrx101.
Thanks for the compressor info, but my question was whether I had to remove the condenser to properly flush it.
Mike

 

Sorry Mike. Everybody usually asks about the compressor (nearly every single time). I wasn't paying close attention.

Ideally yes, You would remove the condenser to "slosh" the solvent around. Since you didn't have a catastrophic compressor failure, flushing it in place should be fine though. Just flush it in both directions and use lots of compressed air to dry it up inside. Same for the evaporator.
Creative use of heater hose and clamps will keep the mess to a minimum.

What are you using for solvent? Have you got a good air supply?

It's awful hot and smoky where you are. Here... . They're on me.

 

I have a small compressor for my nail guns. I haven't bought any flushing solution yet.
Mike