AC Issues

[RobbieD]

That is a good thought, but I wouldn't think that would keep the compressor off almost entirely at higher RPM's. I could be wrong

Good point; the system would probably short cycle instead. MAKG's thoughts make sense, and I hope that you get it squared away with the least amount of hassle. Good luck!

 

[skippy]

it is hard to diagnose with out seeing the gages hooked up and being there to look at the behavior of your system but the info you have supplied us with suggest a system low on refrigerant,enough left to bring on the comressor but not enough to sustain the pressure above the low pressure cut-out setting of the lp switch or as whats-his-name said a high side restiction starving the low side and tripping the lp switch.in any case you mentioned access to a shop and proper equipment,put the gages on it,run it and see if low press drops out of sight,high side climbs out of sight just before it cycles off.if you have a halogen leak detector run a leak check at all connections and along the hoses,if you find a place that the leak detector acts up back up the detector with soap bubbles.pm me if you want,if your close to douglaville i can help you with it.good luck.

 

[jv982]

I am going to throw the guages on and see what I can see. I have access to an a/c machine, a refrigerant "sniffer". Unfortunately I do not have access to a machine that flushes out the a/c system.

Thanks for the offer... If I need assistance I will let you know.

 

[skippy]

i don,t have a machine to clean out either,we use dry nitrogen in residential/comercial systems for pressurizing systems for leak checks and flushing out systems.just a thought,pressure swiches go bad and i looked at mine,its out of the truck and it has a slotted screw between the wire terminals.if the system cuts out around 30 psi its probably best left alone.

 

[Boomer]

First of all go back to his first statement..."high pressure line doesn't get cold"...high pressure lines don't get cold when they are charged right...system is low

Next...at the end of last year a little frost formed on the high line...the only way that happens is when the freon boils off comming out of the condenser due to LOW SYSTEM PRESSURE. You have to maintain high pressure to keep that stuff from boiling off to soon (like outside the evap tubing). Think of it this way. Water boils at 212 degrees at sea level. Put a glass of water in a bell vacuum jar and drop the atmospheric pressure and the water will boil at room temp. Bottom line and most importantly as stated by MAKG...if system pressures are low you need a shop...in the very least you need what a shop has to do the job right.

 

[jv982]

First of all go back to his first statement..."high pressure line doesn't get cold"...high pressure lines don't get cold when they are charged right...system is low

Next...at the end of last year a little frost formed on the high line...the only way that happens is when the freon boils off comming out of the condenser due to LOW SYSTEM PRESSURE. You have to maintain high pressure to keep that stuff from boiling off to soon (like outside the evap tubing). Think of it this way. Water boils at 212 degrees at sea level. Put a glass of water in a bell vacuum jar and drop the atmospheric pressure and the water will boil at room temp. Bottom line and most importantly as stated by MAKG...if system pressures are low you need a shop...in the very least you need what a shop has to do the job right.

Please excuse my typo.... I am surprised you caught it as no one else did, or maybe they just knew what I was trying to say. I will edit it in the orginal post as well..... I meant the low pressure line after the accumulator.

 

[skippy]

i understood what he was saying.

 

[envious8420]

pressures above 300psi-500psi(edu guess)
sounds like it may also involve a pressure switch

 

[MAKG]

The pressure relief valve is supposed to pop at 450 PSI. Other high side leaks are unfortunately likely to show up well below that.

I doubt this involves the pressure switch, but it can be jumpered if needed.

 

[skippy]

when i get around to the a/c phase of my resto i will have a high side safety swich w/manual reset set below the relief valve setting.

 

[MAKG]

Bad pressure switches are MUCH more likely to be always on or always off, then just cutting out during operation. Or else they can get leaky. Note that these are tunable, so if they always cut out at 30 PSI, you can tune them to cut out at the proper 24 PSI. Or even a bit lower for R-134a (too low forms ice in the evaporator core and makes the airflow bad).

 

[skippy]

i know,im talking about adding a hp cutout as added protection.i have my accumulator and hoses off right now,i looked at the lp switch last night and was supprised to see the adjustment screw.don,t see that in my field unless its a bulky metal box with cap tube in various lenths ending with a 1/4" flare nut and a 1/2" conduit knock-out. our encapsilated switches come in various cut in/out settings some with 24"leads and some without but none i,ve seen with that adjustment screw,thats just plain cool.now that i know i,ll bench test mine w/dry nitrogen before i put it in.when i add the high pressure safety i will have the manual reset variety so i have to check it if it ever toggles.im in no hurry to get the air going,not my dd.need to make it more road worthy first.24 psi seems a little low but ok.