A/C's been out for several years - don't know why. About a year ago, I tried one of those R12 - R134 cheap conversion kits, thinking maybe the R12 was low or completely out. How ever many cans of R134 it came with, I dumped in. The compressor never kicked on and I gave up. If this happened to be a low pressure switch problem, should I try this again bypassing the switch? Any danger in freezing up the compressor by forcing it to come on this way? Any other ideas? I'd really like to get the A/C working again but not with spending a lot. Thanks.

 

There was no way that even the first can of 134 went in completely without the compressor "sucking" it in while the clutch was engaged ? You can jumper the cycle switch on the drier temporarily while recharging......you can also lay the can sideways to speed up the process if the suction port is at the drier.........when the can is empty it will feel warm all the way across the can

 

Thanks. I do not recall the compressor ever engaging as I was attaching each can of R134. Are you saying the cans of refrigerant never emptied? The low pressure switch is on the accumulator. I jumped it momentarily and the compressor clutch engaged. What's my next step? Jumper the switch and put in another can? To replace the switch, does it just screw off the accumulator without letting any refrigerant escape? A lot of questions. Thanks for your help.

 

Ok now you must have a gauge in order to continue.......hook up the gauge on the low side(drier).....if the pressure is above 70 while A/C off......start the engine .....turn A/C on to MAX and at least medium blower speed.......come back to the engine bay to see if the clutch has kicked in..........if the clutch did not respond....jumper the cycle switch.....it should start pulling the pressure down.........if the pressure drops below ..say...30 while idling and keeps dropping..........you need to add freon........you can spray soapy water on the A/C fittings and components in the mean time to see if you have a RAPID leak....take the jumper out if the pressure drops below 20 psi at any time.....if the pressure stays up above 20psi ...remove jumper and plug back into cycle switch.....the ideal pressure is around 35 psi idling (depending on outside temps) towards 25 psi while at fast idle and cruise RPM's (small screw between switch blades can be twisted to allow a lower cycle point..22 to 25 for R134) before the clutch cycles with R134....there are many variations too my suggestions....at least this will get cool air at the vents!

 

Thanks for your suggestions. I did hook up a gauge (one of the cheap ones that comes withn the conversion kit). Almost no pressure at all. When I jumper the switch (I do this for a split second), the clutch spins. Should I jumper the switch and try to get the compressor to suck a can of R134/oil in? My other fear is that the compressor has been out of service for so long that the seals are shot.

 

The reason for hardly no pressure is that there is a leak or leaks in the system......while the system is that low......you may want to reseal the easy stuff like the orings for the hoses at the compressor , the 2 hoses , the condensor,the orffice tube,the drier, etc......if you in fact do have a leaky evaporator...or a leaky compressor assy.....that's a whole 'nother job.........all in all.....if it takes 3 to 4 cans per season......you can either live with that cost......or bite the bullet to get it done completely

 

Thanks, Phillip. I appreciate your help. But will it hurt to do as I asked? That is, jumper the switch and feed in a can or two of R134 just to see if the pressure comes up and the air gets cold?

 

At this point I dont think it will hurt. You are looking for about 35-40 psi at idle, not "a couple cans" It takes 15% less 134A than R-12. It may not last long depending on the size of the leak. You also need to worry about the old mineral oil in the system from the R-12 mixing with the Pag/Ester 134A oil. It may work 15 minutes or 15 years. Try not to feed too much liquid to it (keep can pointing up) or you might kill the valves in the compressor.
When it does crater you need to do it right.

Good Luck,
Justin

 

No luck. Fed in a can of R134a Plus (includes oil, o-ring conditioner, stop leak, leak finder dye) while jumpering the switch. The pressure rose to 25 psi but then dropped to 0 almost immediately.

 

Must be a very fast leak......

 

Get a hand held black light and shine it around the hose connections, it there's a leak you'll SEE it.