chassis AC AGAIN

[cannon man]

OK, HAD A CHANCE TO RUN IT TODAY. ABOUT 75* OUTSIDE. AIR DOORS SEEM TO BE WORKING PROPERLY. NO HEAT THROUGH HEATER VALVE.
AC ON MAX. FAN ON MAX. LOW SIDE PREASURE ABOUT 30#. COMPRESSOR IS CYCLING EVERY 10 SECONDS. NO COOLING AT ALL. NO FROSTY HOSES. HEADING BACK TO AZ SOON.
ANY IDEAS????
THANKS, DAVE

[cannon man]

still lookin for help. the low side presure stays at 30# when the compressor is cycling. should'nt the presure go up some before it cuts out. i'm thinkin the cycling switch is bad. ?????????????

[angelman]

You can try to temporarily override the switch with a jumper and see if the pressure comes up. Could be the low or high cut off switch.

[M&EM]

Check high side if you can. My guess is low freon. At 30# on low side, low pressure switch should cut off compressor. Caution---If you over ride low switch, compressor may not get enough oil lubrication if freon is low.

Marty

[cannon man]

thanks for that. what should low side pressure be at?

[mfire1339]

If it were low on freon it would go to a vacuum.

Mike

[M&EM]

Dave, I can't remember the numbers and don't have my gauges with me to look at. I 'd guess at 35 to 40s. Depends on air temp going thru the evaporator. I wont be back in phx til Tuesday. If no one else chimes in I'll give you a better answer then.

Marty

[M&EM]

Quote:

Originally Posted by mfire1339 If it were low on freon it would go to a vacuum. Mike

Mike, maybe. I think the lowest pressure would be what ever the low limit switch shuts down at. The system is designed to operate with freon and oil mist. If allowed to go to zero(vacuum)no oil mist present no lubrication and no more compressor. Low freon or very low ambient are two possible conditions I know of to cause low limit switch compressor shut down.


Marty

[speed racer]

You need a set of gauges to get the readings on both sides. If it has too much freon the high side will be high and cycle the compresor with the high pressure limit switch on the other hand if it is low on freon it will cycle the compresor on the low pressure limit switch. In both cases it will not cool.

[cannon man]

thanks for all the info.
how do i know if the high is high or the low is low if i don't have the specs? where can i find them? dave

[DriVer]

Quote:

Originally Posted by cannon man thanks for all the info. how do i know if the high is high or the low is low if i don't have the specs? where can i find them?

Dave, I'm just watching this dialog and the question has come to my mind as to whether or not you are up to speed with working on the air conditioning system. It just seems to me like you thrashing ... perhaps I'm mis-reading what you're putting down.

[DancinCampers]

My experience has been that a short cycling compressor usually indicates low freon level. Jumpering the low pressure switch should confirm.

Another possibility is the metering device. Not sure which kind is involved, but if it is not opening properly, or is plugged, the system will short cycle because the freon cannot pass thru fast enough to satisfy the compressor, and the low pressure switch will open. I would not think this the cause on a system as new as yours, but it is possible.