DRASH Unit AC issue

Maybe this is in the right location but anyway.

I have a 2008 DRASH unit, generator works perfectly but my issue lies with AC unit itself. Specifically getting the AC compressor to start and pump. If the soft starter starts the compressor, you can hear it run but it will not pump the refrigerant (verified by gauges).

However, I can manually press the contactor in on the soft starter with a screw driver and the compressor will start and pump.

anyone had this issue? I’m leaning towards a bad soft starter but not sure if something else would be tripping the thermal overload on the compressor. The soft starter itself is not tripping or throwing a fault code. Picture is of the soft starter I’m dealing with. Timers seem to be working as they should as it does delay when the call for cooling is on before it tries to start.

I think there is a schematic on one of the doors. What gives the contactor the impulse to close the contactor?

Guyfang said:

I think there is a schematic on one of the doors. What gives the contactor the impulse to close the contactor?

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I have the schematic for it, the 24v runs through all the pressure switches and given all you those safeties are closed, the 24v goes to a relay and then into the contactor. The starter pulls in like it’s supposed to and stays pulled in but the compressor is tripping out on something. Unless I just hold the contactor in, it runs fine. I’ve even tried doing the 100% initial torque and 0sec ramp time to simulate just mashing the contactor in and it won’t start it and pump. The compressor runs but won’t pump. Never heard of that but there is a sticker on the compressor that says it will do that if tripped on thermal overload. System is not overcharged either

And you have tried to jump all the pressure switch? I would jump the whole pressure/safety circuit and see if it kicks in. If it kicks in, then you at least know where to start. One switch at a time.

Guyfang said:

And you have tried to jump all the pressure switch? I would jump the whole pressure/safety circuit and see if it kicks in. If it kicks in, then you at least know where to start. One switch at a time.

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Yes, on these, in order for the soft starter to actually engage with the 24v. The 24v has to flow through all of the safeties in order for it to pull in and I have traced where the 24v comes out of the last switch and I have 24v which then runs into a timer and a relay which then tells the soft starter to pull in and start the compressor.

However the soft starter pulls in like it should but the compressor unloads and wont pump. Only unloads when the soft starter starts the compressor. Manually started by just pushing the contactor in at the soft starter with a screwdriver, compressor starts, pump and cools like it should, condenser fan follows in correctly etc. it’s just getting the soft starter to start the compressor. I just don’t know if there’s something else I’m missing that’s causing the compressor to unload. I don’t know is somethings up with the lower half of the soft starter and somethings not closing or what’s up with it.

Is the contactor getting any voltage at X1/X2, (The coil on the contactor?)

Guyfang said:

Is the contactor getting any voltage at X1/X2, (The coil on the contactor?)

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Contractor has 24v to it and once the 24v has run through all the safeties and switches it completes the circuit and closes the soft starter.

I’ve been told that timers are an issue on these as well. And that it could be something between the hot gas valve and the “cool” switch causing the compressor to unload. So it may not be the soft starter, not sure yet.

I keep the switch on “vent” when I hold down the contactor manually as I don’t want it trying to pull in while I’m holding it. So right now I’m looking into the timers and relays in between that valve and the switch

Good Day. I'm Dave. This is gonna sound funny, any way to find out what model your working with? I'll bet I have the info your looking for but everyone called a gen trailer with an ECU on it a DRASH and there are about 30 different models and they do not all have the same things in them. I have seen the motor starter in the PICs on about 12 different ECU units from different manufacturers. Before I open my mouth and mention something about a bypass valve and several open in different stages it would be great to know what model. Compressors are almost all vain type and some are variable vain type. So far you seem to have a motor starter with pitted or bad contacts. Try removal, clean or burnish the contacts and try again. I probably have factory settings if you did not write them down.

LuckeyD said:

Good Day. I'm Dave. This is gonna sound funny, any way to find out what model your working with? I'll bet I have the info your looking for but everyone called a gen trailer with an ECU on it a DRASH and there are about 30 different models and they do not all have the same things in them. I have seen the motor starter in the PICs on about 12 different ECU units from different manufacturers. Before I open my mouth and mention something about a bypass valve and several open in different stages it would be great to know what model. Compressors are almost all vain type and some are variable vain type. So far you seem to have a motor starter with pitted or bad contacts. Try removal, clean or burnish the contacts and try again. I probably have factory settings if you did not write them down.

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This is it. 35KW generator, 8 ton AC.
I think these were set at 16% initial torque at 10 second ramp time (if that’s right). Once the refrigerant equalizes the soft starter will start it and the compressor will pump but the compressor will overload after about 5 seconds of running and stop pumping. When checking power through the soft starter, correct voltage on all legs is coming out of the top when it’s pulled in. It’s a 2008 Powersystems international. Model on the plate is 2003850. I have sprayed the starter with contact cleaner. Can those be taken apart and reassembled easily for cleaning ?