Intermittent working AC

[alpac]

Hi, When I bought my 4.0l 1990 Ranger 4months ago it was in pretty good condition but I noticed that the AC did not work. When the weather started get warmer over here few weeks ago I recharged the AC and since then it has been working erratically. Sometime it works and sometime it doesn't. Within 15mns it would go from cold to no cold. The pressure seams OK and if there was a leak I would think that the AC would stop gradually to make any cold which does not seam to be the case here. I was thinking about may be an electrical problem as I noticed that when it stops making cold and if I repeatedly press the AC button it will eventually start getting cold again. Could that also be a failing compressor? Any suggestion what I should start trouble shouting? Thanks in advance and BTW great article from MAKG

 

[alpac]

Hi, When I bought my 4.0l 1990 Ranger 4months ago it was in pretty good condition but I noticed that the AC did not work. When the weather started get warmer over here few weeks ago I recharged the AC and since then it has been working erratically. Sometime it works and sometime it doesn't. Within 15mns it would go from cold to no cold. The pressure seams OK and if there was a leak I would think that the AC would stop gradually to make any cold which does not seam to be the case here. I was thinking about may be an electrical problem as I noticed that when it stops making cold and if I repeatedly press the AC button it will eventually start getting cold again. Could that also be a failing compressor? Any suggestion what I should start trouble shouting? Thanks in advance and BTW great article from MAKG

And I forgot to mention that this truck had been retrofitted by the previous owner

 

[alpac]

I also noticed that when the compressor clutch get powered it only does for 10s or 15sec and then the compressor stops and then will get powered again 40sec later.

 

[MAKG]

I'd put a pair of gauges on that. Otherwise, you're just guessing. In particular, what is the high side doing when it shuts off? Is it turning on based upon the low side pressure like it is supposed to? This would rule out an electrical problem.

And, are those cycle times at idle? Is it really hot out? Is the control set at max A/C on full cold?

 

[alpac]

I'd put a pair of gauges on that. Otherwise, you're just guessing. In particular, what is the high side doing when it shuts off? Is it turning on based upon the low side pressure like it is supposed to? This would rule out an electrical problem.

And, are those cycle times at idle? Is it really hot out? Is the control set at max A/C on full cold?

MAKG,
Thanks for your response. Control was set at max A/C and yes these cycle times are at idle.

 

[alpac]

I measured the pressure today at the low pressure side and it read 45 PSI. It went to 65 PSI after running the engine for 5mns. The Compressor engaged continuously first and then stop and then engaged every 20secs for about 5 secs. No more cold was coming from the vents. Could it be a clogged orifice tube? By the way where is the orifice tube located? Is it easily accessible?

 

[MAKG]

What is the HIGH side doing?

You can't diagnose a restriction based only on the low side.

 

[alpac]

What is the HIGH side doing?

You can't diagnose a restriction based only on the low side.

I need to find the right adapter for the high side as my gauge adapter works only for the smaller low side connector. Went to the nearest autozone and they did not have an adapter for it.

 

[MAKG]

Umm, STOP.

The pressure relief valve kicks in at 450 PSI. Normal operation won't go that high, but you don't know you're in normal operation. If you "adapt" a low side gauge onto that, you'll blow it up and send yourself to the hospital.

Take this into a shop if you aren't going to do it right. I guarantee it's cheaper than the emergency room.

 

[alpac]

Umm, STOP.

The pressure relief valve kicks in at 450 PSI. Normal operation won't go that high, but you don't know you're in normal operation. If you "adapt" a low side gauge onto that, you'll blow it up and send yourself to the hospital.

Take this into a shop if you aren't going to do it right. I guarantee it's cheaper than the emergency room.

Thanks for the warning. I will look for a gauge specifically for the high side. I have avoid emergency rooms for 49 years and I want to keep it that way as long as possible .

 

[Earl43P]

Harbor Freight sells an R134a gauge set for $39.

Good enough for limited usage by a backyard mechanic.