CAT 299D2 HPX AC problems

[PlowBoy_TX]

This has been driving me nuts. I have a CAT 299D2 HXP that the AC was working, then just stopped.
The compressor clutch kicks in for less than 2 seconds and kicks out.
Here is what i have replaced.

*Wiring harness from compressor/relay/pressure stitches to under cab.
*All controls on the operator panel. Thermostat / Switch / Fan speed selector.
*New relay.
They all had some type of damage so i just replaced them.
I tested the pressure switches and they tested fine.
I checked freon level and its perfect.
If i jump across the relay plug, the compressor runs and cools so i swapped the new relay out for another new one and nothing. What am i overlooking?

 

[Nige]

Have you replaced the accumulator.? If I'm not mistaken it also contains an non-serviceable orifice which tends to block, so if it does you have to replace the whole assembly.

 

[ahart]

What do the pressure gauges read when the compressor kicks out? I would have to assume it’s only doing what it’s told to do.

 

[PlowBoy_TX]

With a jumper on the relay plug and compressor running im getting 147 high and 31 on low side.
without the jumper, the compressor is only on for a spilt second and the gauges cant respond that fast.

 

[PlowBoy_TX]

Have you replaced the accumulator.? If I'm not mistaken it also contains an non-serviceable orifice which tends to block, so if it does you have to replace the whole assembly.

View attachment 311298

No we have not changed the accumulator. Wouldn't i get funky readings on the gauges if it was blocked?

 

[ahart]

Have you tried a jumper wire in place of the pressure switch?

 

[PlowBoy_TX]

Have you tried a jumper wire in place of the pressure switch?

Yes i tried jumping them one at a time then both at the same time

 

[heymccall]

Have you jumpered the thermostat switch?

 

[PlowBoy_TX]

I have not tried it but that's the next thing on my list to check. Been out of commission for a few weeks

 

[LN Pipeline]

So is the thermostat new? Pull the thermostat probe out of the evaporator and see if the compressor stays running.

 

[Arny L]

If system operates, when relay jumped, it sounds like you are missing the ground side of relay, or a 12v input to that relay, Depending on how its wired, most are ground switched, ECM controlled. But it could have continuous ground, ECM switched 12v.