need a little info 1993 explorer ac system

[daddynuz]

I'll try and give as much details as I can. My 1993 explorer was converted professionally to R134a ran fine for a year got low on refrigerant added roper amount of r134a with a stop leak additive included. ran good all last season then High side pressure hose blew. let it alone through the winter. replace entire manifold with new. pulled a vacuum and it seemed to hold 28-30 lbs. charged system to about 40lbs compressor short cycled for a short time as gas was entering system then it ran steady till I hit 40 lbs. ran car and system for about an hour. shut down car. a few hours later restarted car and system was still switched on a few seconds after starting I heard a hissing sound and saw some vapor cumming from under the car compressor started to short cycle and took reading and pressure gauge was bouncing from 25-60 on the scale. I also did (what I thought) was a through leak test with an electronic tester did not detect any leaks when I charged system after manifold install. I was told by an old ac guy ( mostly residential experience that he thinks it is a bad pressure relief valve some where on the high side of the system. visually searched for that valve but not sure where to look also tried to search parts lists and I can not find 1 listed. Any an all suggestions for trouble shooting this system would be appreciated

 

[ranger7ltr]

The hissing was from the high pressure relief valve...

When you "fixed" the system, did you replace the accumulator? If not that is problem #1...

If you did, how long did you vacuum the system down before charging it? And did you replace or at least remove and look at the orifice tube?

And finally, you really need to get a proper set of gauges to monitor the high side as well as the low side pressures...

Low side will tell you very little in the way of how the system is working...high side pressures are most important to see if the air has any air in it, if there are any clogs in the system, and whether or not the condensor colling is proper and to determine when to stop on a retrofit on charge level...

Personally I prefer to charge by weight but on a converted system that is not accurate so you have to start at 60-70 % of the R-12 charge level and go from there...

 

[BobWiersema]

Personally I prefer to charge by weight but on a converted system that is not accurate so you have to start at 60-70 % of the R-12 charge level and go from there...

Always charge by weight. I have the formulas someplace around my desk for the conversion to 134a. (Its not the same weight that the tag says for 12)
Post your R-12 weight and Ill do the math for you.

Sounds like you may have overcharged it and blew a relief valve somewhere. Im not sure where that is but I would think the back of the compressor. Once those things open they never reseat correctly. Try pulling a vacuum on it and see what you get.

Bob

 

[daddynuz]

ok thanks for the replies.. did not touch accumulator or orifice tube trust a replacement of both will be a good start ( not sure where to find orifice tube will have to search for a component location guide) did charge by weight was told to go 75%-80% of R-12 listing on system. pulled vacuum for about 20 mins. before charge. I see that there is a pressure relief valve on the back of the manifold from the rear of the compressor is there another as hood was closed when it blew I could not see where the gas was coming from also are these valves replaceable can't find them listed at my parts store website??? another input I got was if there is a clog on the high side system will cool down for a while but eventually will blow off on pressure?? now next question: do you feel a system flush would be in order I thinking that I could have a problem as I put some stop leak in with the last 2 charges.

 

[BobWiersema]

A/C Conversion

80% of the R-12 is correct. When you say that you converted it to R-134a what exactly did you do? Did you add some POE oil? Did you replace anything?
Your truck should have a FS-10 Compressor, that should have no problem with 134a but 134a will not carry the original mineral oil from R-12, it will stay in the compressor, and that's just fine. But you do need to add about 3oz of POE oil to lubricate the rest of the system. Any R-134a oil charge should work just fine.

And dont put any more of that stop leak crap in it. That can gunk things up.

 

[daddynuz]

well I think the right course of action at this point is to flush system, replace accumulator and orifice tube then reassemble ..pull vacuum for 20 mins. and then see if it holds if it does I will add 22.5 oz by weight of 134 also 2 oz pag oil is what I was told to use with R134 if the vacuum does not hold I guess it will br time for a freon nitogen mix to see if I can find a leak. but from my research and the replies I think there may be some type of blockage on the high side and thats why it will blow off after awhile

 

[BobWiersema]

well I think the right course of action at this point is to flush system, replace accumulator and orifice tube then reassemble ..pull vacuum for 20 mins. and then see if it holds if it does I will add 22.5 oz by weight of 134 also 2 oz pag oil is what I was told to use with R134 if the vacuum does not hold I guess it will br time for a freon nitogen mix to see if I can find a leak. but from my research and the replies I think there may be some type of blockage on the high side and thats why it will blow off after awhile

I never suggested flushing the system. Most of us dont have anything like a Robinair Charger with Flush. A 4 thousand dollar tool just for working on the a/c is a bit much.

Also I have never heard of mixing nitration with 143a, but what do I know, 25 years in the business you cant know it all.

Read your responses before posting.
Dont ask for help if you dont want it.


End of Thread............





Bob

 

[daddynuz]

fyi I was planning on a manual flush taking all parts off and doing them by hand with blow gun might use nitogen to help remove moisture as far as the leak if there is one the plan there was to use r22 & nitrogen to find it

thanks

 

[Anime]

"Professionally converted" means little. There are know-it-alls at A/C-specific shops who convert an R12 system by threading on R134a fittings, charging the system with R134a, and calling it good.

A good conversion would entail not only replacing the hoses with barrier type units, and the o-rings with green HNBR ones instead of black rubber, but also replacing the receiver/dryer with a newer one made for use with R134a. And that's at a minimum. Flushing the condenser and evaporator, and use of the correct oil goes a long way towards ensuring the long life and safety of a system. Even better is using Nylog on the o-rings and seals, and using a variable orifice tube.

There's other considerations, too. Lots of 1993 and earlier Explorers came with the FX-15 A/C compressor. It's not considered strong enough, including by Ford, to handle the pressures of R134a, so a switch to an FS-10 compressor is needed to avoid black death or destruction of the entire system. Use of a R134a low side pressure switch on the receiver/dryer should also result in proper compressor performance.


You can get A/C cleaning solvents at the parts store, no need to use nitrogen or anything. You can also follow up with some alcohol for an extra clean system. R22 can be used in the system to check for leaks, provided you have some method of recovery to remove it and put in the proper refrigerant.