STRAIT A/C TROUBLESHOOTING HELP WANTED

I have been working on a strait a/c system for a friend , they ask me to look at it since I have been in the field for a couple of years now. here is what I found. T he unit has not run in several years according to my friends. WHEN i STOP BY THE FIRST TIME ( 1-WEEK AGO)I turned the unit t- stat to fan on the blower started up so I knew the transformer was good ,I then turn the a/c on the compressor started up I put on my gauges , no pressure I cut the unit off and depressed the high side schader , very , very little pressure release. SO i get my jug of r-22 and charged system to 12 deg superheat and a s.p of 65 psi and a head pressure of around 200 psi outdoor temp around 86 or so. all ran good all week they complained the house was now to cold. 1 week later they call me and tell me its blowing hot air. im thinking loss of charge i had no way to leak search privously, when i return there i turn the tstat on copressor fires up i put my gauges on it reads 85 psi sp 182 head psi 30 deg super heat 7 deg subcooling 10.9 amps on compressor after 20 min. it cuts off. i figure the stat was satisfied for they had been running a window unit. SO I OPEN THE DOORS TO HEAT UP THE ROOM AFTER ROOM TEMP AROSE TO 78 I TURN STAT ALL THE WAY DOWN . this is a 95 unit and a very old t-stat (mannual not digital). compressor still will not start. I check low voltage across contactor coil, it was not pulled in and no power. i then checked wiring between yellow and common it read 26 volts . it has some kind of relay or it looks like a small control board with 2 diodes and 2 resistors on it an the leads from the contactor hook there, i checke voltage across it i had 26 volts. i could put a jumper on it across one leg of power from the contactor and common it would start up. i then removed the jumper it kept running, but my sp was still way high and my head psi was still a little low even after running 15 minutes low sub cooling and high super heat it acts like a valve in the compressor going

hvac tech12 in Concord, North Carolina said: I ran out of space, it acts like compressor vaves going bad but my amp draw is still normal what are your thoughts anyone

hvac tech12 in Concord, North Carolina said:

Call someone who knows what they are doing. HAHA

It sounds like you gotta look in the book. If I knew anything about this stuff I'd help but sry.

there is alot of stuff that could be wrong. Zero is supposed to be read across red and yellow. Did you check the Low pressure, High pressure switch Its on the cooling line (yellow wire on the t-stat). you should read zero cause its a switch. It could be that you just undercharged thats the reason why you have low SC and high SH. The TXV is trying to maintain a constant super heat. I would take out the charge and recharge it by weight.( its on the nameplate). if it was the comp. valves your gauges would read high on the low side and low on the highside.
PS you could get fined up to $30,000 for the release of refrigerant into the air.

hvac tech12 in Concord, North Carolina said: I have been working on a strait a/c system for a friend , they ask me to look at it since I have been in the field for a couple of years now. here is what I found. T he unit has not run in several years according to my friends. WHEN i STOP BY THE FIRST TIME ( 1-WEEK AGO)I turned the unit t- stat to fan on the blower started up so I knew the transformer was good ,I then turn the a/c on the compressor started up I put on my gauges , no pressure I cut the unit off and depressed the high side schader , very , very little pressure release. SO i get my jug of r-22 and charged system to 12 deg superheat and a s.p of 65 psi and a head pressure of around 200 psi outdoor temp around 86 or so. all ran good all week they complained the house was now to cold. 1 week later they call me and tell me its blowing hot air. im thinking loss of charge i had no way to leak search privously, when i return there i turn the tstat on copressor fires up i put my gauges on it reads 85 psi sp 182 head psi 30 deg super heat 7 deg subcooling 10.9 amps on compressor after 20 min. it cuts off. i figure the stat was satisfied for they had been running a window unit. SO I OPEN THE DOORS TO HEAT UP THE ROOM AFTER ROOM TEMP AROSE TO 78 I TURN STAT ALL THE WAY DOWN . this is a 95 unit and a very old t-stat (mannual not digital). compressor still will not start. I check low voltage across contactor coil, it was not pulled in and no power. i then checked wiring between yellow and common it read 26 volts . it has some kind of relay or it looks like a small control board with 2 diodes and 2 resistors on it an the leads from the contactor hook there, i checke voltage across it i had 26 volts. i could put a jumper on it across one leg of power from the contactor and common it would start up. i then removed the jumper it kept running, but my sp was still way high and my head psi was still a little low even after running 15 minutes low sub cooling and high sup

First off have you checked if the filter is cloged. If the unit hasn't run for a while and was empty of refer there could have been corrosion or moisture in the lines that now has circulated and traped in the filter. When ever I encounter the same situaiton I like to replace the filter and pull a new vacume to make sure the lines are clean and DRY. Moisture in the system would explain the slight drop in pressure after refrigerant has cycled. Also like andy pointed out, make sure the TXV is working properly. Is the evap coil icing up at all? Excessive condensate is a tell tale after the unit has run for a while. As far as the power, determine if you have a 2 speed compressor. I've run accrossed units where the second speed won't come on but not the other way but not to say it can't happen, in that case you have a bad relay some where. Next time check for a leak beforehand by carging with nitrogen and I can't empasize this enough, pull a new vacume on units that are in ANY question of neglect or are empty of refer. Good Luck!

im in charlotte nc seeing how it has set for a few years i would pull all refrigerant out of the system then pump it up to about 350 psi of nitrogen get some bubbles and look for leaks if you cant find any visually then let it set for about 1/2 day if you lose pressure then find the leak but what im thinking is that you do have a leak and the system has gotten alot of moisture in it so let it pull a good vacuum maybe 2 days or so you may have to change your oil in your pump after the first day but see if you can get it down to at least 400 microns if it hold and doesnt lose at least 500 microns in 20 minutes then charge the unit by your superheat and you should be good to go i have about 14 yrs experience in res. and comm. hvac and comm. refrigeration so if anyone has any questions i would be glad to help out my email is uwantsumdis@hotmail.com

Check your high voltage tap on your transformer and set it for the proper voltage. Replace the old t-stat,it's probubly causeing low voltage. Pull one wire off the contactor and test for volage between it and the terminal it came off of.
It sounds like you have a time delay relay for the compressor.You can bypass it and get rid of it but I suggest getting a stat that has one built into itself. What type of unit and compressor. is it a split system, Pack, or what.

[Sounds like the thing with the diodes is a time delay relay that either is timing out or faulty) This willl prevent short cycling of the compressor especially with a non digital thermostat.

All of the suggestions are partially correct. You have multiple problems most definetly a leak in sys. With high back pressure a week after charge and high s.h. low s.c. I would check your ducts especially return to make sure its not pulling hot air from attic directly into evap. Most important reclaim charge. Nitro flush system fix leak. change filter drier add drier to suction side also put on long vacuum.

Collin in Spring Hill, Florida said: All of the suggestions are partially correct. You have multiple problems most definetly a leak in sys. With high back pressure a week after charge and high s.h. low s.c. I would check your ducts especially return to make sure its not pulling hot air from attic directly into evap. Most important reclaim charge. Nitro flush system fix leak. change filter drier add drier to suction side also put on long vacuum.

wanna work for a great company? chance in a lifr time?

Here's my approach.

FIX THE LEAK , first.

of course r/r the filter driers or add them.

then Vacuum at least 45 minutes minimum with a micron gauge.

then weigh in the charge, and top it off if needed.

Next, take a delta -t and monitor your gauges , they will tell you everything that is going on.
learn how to read them and what they mean.
;) nine times out of ten there will be a combination of problems, usually a chain reaction....

hvac tech12 in Concord, North Carolina said: I have been working on a strait a/c system for a friend , they ask me to look at it since I have been in the field for a couple of years now. here is what I found. T he unit has not run in several years according to my friends. WHEN i STOP BY THE FIRST TIME ( 1-WEEK AGO)I turned the unit t- stat to fan on the blower started up so I knew the transformer was good ,I then turn the a/c on the compressor started up I put on my gauges , no pressure I cut the unit off and depressed the high side schader , very , very little pressure release. SO i get my jug of r-22 and charged system to 12 deg superheat and a s.p of 65 psi and a head pressure of around 200 psi outdoor temp around 86 or so. all ran good all week they complained the house was now to cold. 1 week later they call me and tell me its blowing hot air. im thinking loss of charge i had no way to leak search privously, when i return there i turn the tstat on copressor fires up i put my gauges on it reads 85 psi sp 182 head psi 30 deg super heat 7 deg subcooling 10.9 amps on compressor after 20 min. it cuts off. i figure the stat was satisfied for they had been running a window unit. SO I OPEN THE DOORS TO HEAT UP THE ROOM AFTER ROOM TEMP AROSE TO 78 I TURN STAT ALL THE WAY DOWN . this is a 95 unit and a very old t-stat (mannual not digital). compressor still will not start. I check low voltage across contactor coil, it was not pulled in and no power. i then checked wiring between yellow and common it read 26 volts . it has some kind of relay or it looks like a small control board with 2 diodes and 2 resistors on it an the leads from the contactor hook there, i checke voltage across it i had 26 volts. i could put a jumper on it across one leg of power from the contactor and common it would start up. i then removed the jumper it kept running, but my sp was still way high and my head psi was still a little low even after running 15 minutes low sub cooling and high sup

hi have you checked the inside filter its sounds like dirty outdoore unit or stoped up evap coil in thr inside

air flow problems if the outside is restreted it cause high suc and low head

this thread is like stepping in a bag of dung on fire. lol