Another ac thread

[DosGatos]

compressor running, blower running, blend doors operating properly.
thermistors high pressure side 650ohms, low pressure 1.25k ohms, piping hot on high pressure side of expansion valve.
blows kind of cold for about 30 seconds then fades to ambient temp with piping on low side of expansion valve mildly warm
same output in cab and sleeper.
guessing thermistors should be replaced and replace expansion valve
yes\no?

[RTRUCKING48]

Replace thermistors,air dryer and expansion valve

[smorgan87]

Build u one them arduino boards rawze designed. Is the compressor running when it goes warm?

[DosGatos]

(07-14-2018 )smorgan87 Wrote:  Build u one them arduino boards rawze designed. Is the compressor running when it goes warm?

It's not a controller issue yet. Compressor keeps running. Big fan doesn't come on so thinking the system is just low for starters.
I'll put some gauges on tomorrow to read the high/low and go from there.

[smorgan87]

Knowing the pressures will tell a lot

[iceman]

Usually when the valve becomes plugged it will ice up around the valve and towards the coil (low side), because the refrigerant pressure is much lower on the outlet of the valve, thus making its temperature much lower. Fairly good starting point on the gauge pressures is 100 condensing temperature and 35 degrees evaporating. Converting the pressures to temperature with a PT chart or on the gauges will show this. Higher ambient temps acroos the coil at the radiator will drive the high side pressures up. Low air movement/plugged evaporator at the cab coil will drive the low pressures lower.

[smorgan87]

I disagree. If ur high side is only 100 psi in this heat (93 here) u have a problem.

[Nilao]

I dont think he's saying 100pai but 100 degrees...

[iceman]

(07-15-2018 )Nilao Wrote:  I dont think he's saying 100pai but 100 degrees...

Correct. Normal systems will run round 110 degrees Condensing temp, which with 134a converts to about 146 Psig on the gauge.