Finally got a set of gauges on my AC, 1990 F150 factory air. R12 system
Ambient 80 deg RH 86% Engine rpm 1300
On start up clutch cycles very quickly.
Low side 30-35 High side 200- 220. Ice on Tube right after orifice. Vent temp 60deg Max air fan on high.
After serveral minutes it seems to stablize and clutch stays engaged most of the time.
Low side 25 High side 280-300. vent temp still 60

Does this indicate the system is low on freon?

History: Got the truck last fall. Late spring realized AC was marginal for cooling the cab. Not knowing the history of the truck, previous owner died, I assumed it might have never been charged. Too many other issues to worry about it. First week in July it was the biggest issue. Cluth was cycling on and off constantly. Guy I know, who seemed to have some decent knowledge of AC system, charged it with ES 12a. I think he had it at about 45psi on the low side. he didn't have an adaptor for the Ford Hi side fitting. Vent temps were unbelievably cold. After few blocks of driving, it would be blowing 50 degree air and after a few miles, down to low 30's. Usually had to use blend door to avoid frost bite. In one month, back to being marginal. Two days ago had it on hiway for 45 minutes. AC running max. Sunny day 95 deg 85 RH lowest vent temp around 62.
Can't really afford to take it to an AC shop. Need help with a plan to find and fix leak. Then convert it to R134a. I can borrow a good vacuum pump.
Don't really have a lot of time to work on this.
Considering putting can of leak detector in and perhaps another can of ES 12a for now. Hoping that will get it thru the rest of the summer and show where the leak is. next spring when I have much more time, trying to do part or all of the proper conversion. I assume that means new drier, and orrifice, and flush entire system. Maybe have a AC shop do part of it.
If I pull a vacuum on it, does that leave the oil in the system?
Suggestions or advice? The only AC system knowledge I have is from reading this forum. No experience working on them.
Do the pressure readings I an getting indicate anything other than low on charge? Like a restriction in orrifice?

Thanks Frank

 

I dont think you want to mix ES-12a (hydrocarbon refrigerant) with R12. I've heard some horror stories about acid formation. You could add another can of ES12a, but it would be illegal and IMO dangerous. You have a leaky system and you're adding a flammable refrigerant to it. Not good. On top of that, you have the remaining R12 in the system, which when it burns, gives you phosgene gas. Also not good.

Anyway, now you have a system that no shop will want to touch it, since it has hydrocarbon refrigerant in it, and even worse, mixed hydrocarbon and R12. Technically, using hydrocarbon refrigerants on a public roadway is illegal, and mixing refrigerants is illegal, regardless of wether it works or not.

What I would do here, is take it to a shop and tell 'em exactly what's been done to the system, and that you need for them to dispose of the remaining refrigerant in the system, and dispose of it properly. Be prepared to pay a hefty hazardous materials disposal fee. The illegal (cheap) way would be to vent it, an activity which I do not condone.

Then, I would look over the system and visually try to find the leak. Usually it will be obvious if it leaks out that fast. Look for a dirty greasy spot on the hoses or compressor. There's your leak.

Here are the things you need from the parts store:
1. a set of R134a compatible o-rings
2. a 8oz bottle of Ester 100 refrigerant oil (not the kind in the charge can, just in a pour bottle)
3. a new accumulator / receiver / drier with R134a compatible dessicant
4. a red orifice tube
5. the snap spring / quick disconnect disassembly tool (I like Napa's metal one)
6. whatever other parts need to be replaced due to the leak

When I fixed the system on my '92 Explorer, I had to replace the low pressure line going to the compressor.

Take it all apart, flush out the things that you're not going to be replacing. I like to use brake parts cleaner, since it dries with no residue. Use your new parts and R134a compatible o-rings, the new orifice tube, pour oil into the system at various locations (IIRC 8oz. is the correct amount) and put it all back together. I like to use this as an opportunity to clean off the condensor since it's out anyway. Charge up with the appropriate amount of R134a or ES-12a (still illegal to use ES-12a but much safer than before) and you're good to go. The way I determine the appropriate amount is to find a pressure / temperature chart and charge by that.

Good luck.

 

Thanks for the advice. Once I get the problems resolved I plan to do a real conversion to R134a. Is the red orrifice tube optimun for 134a? Do the pressures I now have indicate a low charge only?
Frank

 

I believe so, yes. I have the red orifice tube in my converted 1992 Explorer system, and it works quite well. Depending on the compressor and size of the system, you may need a bigger one. But from what I hear, on most Ford R12 to R134a conversions, the red one works best.

This part really depends on ambient temperature and refrigerant used. As yours is an unknown mixture of R12 and ES-12a, I dont think you'll find a pressure / temperature chart for that. But since the compressor is cycling, and it has a leak, that probably means it's too low. I honestly wouldn't run it any more with this mixture of refrigerants, due to acid formation, which can and will eat lines, seals, and your compressor.