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2006 630 D12 A/C Problems


txdslshop

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I was hoping someone who could point me in the right direction. WhenI bought this truck the compressor would not come on and it only blew hot air. Now that I have the bed going my way I have dug a bit deeper into the a/c issue. It was missing the high side schraeder valve and after an hour long vacuum it held and I decided to throw some 134A at it. Charged it with 3.75 lbs and the compressor kicked in and ran for maybe 20 seconds. The low side cam down to roughly 30 and high side was up to maybe 150. Then the compressor kicks out and then will only cycle on for roughly 4 or 5 seconds and off for maybe 20-30 seconds. The power to the clutch coincides and is apparently being commanded off or is losing power. I did make a pigtaile and powered the clutch directly and the compressor runs and presures stabilized at 25/150 with the fan clutch locked in constant. Any ideas? Or maybe someone who knows where power is fed to the clutch from? I spent some time in the fuse panel on the top of the dash and nothing jumped out at me. Didnt see anything labeled a/c compressor. I would sure appreciate and help or direction. Searching hasn't turned up much. Jeremy

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my guess is the low pressure switch is opening while getting to 30psi on the suction/low side of the system. 30psi equates to the refrigerant having a boiling point around 35 degrees F. around 25 psi the refrigerant is boiling at 29 degrees F.

 

problems with low suction have to do with low load, low air flow, dirty evaperator. These are all things that inhibit heat transfer on the low side of the system.

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I was planning on tearing into the dash evap tomorrow as I dont like the air flow coming out of the vents. I wasnt sure on jumping the low pressure switch as it appears to have 3 or 4 wires. Does anyone know how to jump it an what each wire is? Thanks for the help!!!

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The pressures indicate to me you don't have enough refrigerant in it yet. Do you have enough airflow over the condenser while you are servicing it? Did you add any oil? The r134 systems are sensitive to the amount of oil in the system. There are lots of things that could be causing it to trip the low pressure switch.

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Ok, spent a few hours on this thing today.... I disassembled and cleaned both evaps and verified correct amount of freon. No change. Compressor still only kicks in for a few seconds and cycles off for roughly 20 seconds. I did disconnect and checked a few plugs and managed to set a High pressure fault code. Once it was reconnected and I cycled the key on to clear it, it would not clear using the dash diagnostic display. I also noticed that the stepper motors do not move the blend doors when the unit is running. For example, you can have it set to defrost and switch to normal forward vents and nothing happens. Let it run for 10 minutes and nothing. But, as soon as you turn the key off, the doors move to the correct position. This thing is quite frustrating. I am wondering if the odd behavior could possibly be a bad module? Anyone have any ideas? Thanks. Jeremy By the way, I have awesome air flow and sparkly clean evaps now.

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Honestly, I am fairly certain that I have tried most every combination to try and make heads or tails of what is going on. But, I can not say for certain that I specifically pushed a/c off button and cycled fan on before deselecting a/c off button. I will certainly try it. And I certainly don't mind bypassing anything to troubleshoot. But, I have pretty much worked exclusively on Dodge Diesel for almost 20 years and my Behr A/C skills and knowledge are lacking. ;)

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If he has owned the truck, the operation ritual should not change overnight.

 

The good things that you do know with your trouble shooting so far.

 

The clutch is operational

The compressor makes pressure

The expansion valve is at least open

The evaporator is getting enough compressed refrigerant to operate.

 

Someone above wrote about the system being sensitive to oil quantity, that may be worth investigating.

 

The other thing that would be worth investigating, is the thermostat. Rather than throwing parts at it, you could verify all your voltage is present to the thermostat and from it, going to the clutch.

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I appreciate all of the input on this!!! I bought the truck the end of last year and knew that the a/c was not blowing cold then. So, unfortunately I have no clue as to how long it has been down or have any idea of things that have been done to it. Having said that, I haven't had any luck finding anyone to tell me specifically how that control system works on this or been able to find a decent diagram that I can decipher. I surely don't claim to be an electrical genius. But, I can usually get things figured out. I did notice a temp sensor by the front evap and of course the high pressure switch on the firewall. But, I am not sure how power is routed from the module and specifically what wires do what on each plug. I have a decent amount of knowledge on how most auto a/c operates. But, like I said earlier, I have limited all of my work to Dodge trucks as I own a specialty shop working on only Cummins trucks for a long time. If this was a fueling issue or a bad cylinder in a 5.9 or 6.7Cummins... I would be golden!!! LOL Please be patient as I am slightly Volvo challenged!!

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It's been a few years since I did HVAC/R, but from what I see you are still a bit low on refrigerant. You will want to see about 35psig (IF memory serves me correctly) on the suction side. You say you put in 3.75 lbs refrigerant. Was that from a sticker on the truck? If it was, did it account for the bunk A/C also? It sounds like the compressor is cycling on the low pressure switch.

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The truck sticker actually said a bit less. I have ran it at the truck listed amount and bumped it to 3.74 lbs and now it is at 4lbs and no change. The compressor only cycles on for a few seconds and cuts off before the pressure even stabiliizes. Low pressure never even gets below 40 before it cuts off. Thanks. Jeremy

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Check the pressure switch leads for changes in voltage while the compressor is cycling on and off.

 

The leads that change should be the contacts that are changing. Pull that lead that changes and apply voltage (if it gets voltage only when compressor runs)

 

Confusing?

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Just another thought. Previously you said the rear ac blew cold air. That's says the system is working on rear controls. If that is true then it is in the control part on the front.

I am no way a ac person, but is there any coldness on the suction line to the compressor. I think it should be getting cold near the end of the suction line. Not frosting at the compressor but getting close.

If not then there is not enough liquid in the lines.

 

Again I am not a a/c person. This may not help but something I have seen done.

 

Safe Travels, Vern

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The rear was blowing cold when I hot wired the compressor. Without hot wiring the compresor, the clutch only engages for a few seconds and then cycles off. Not sure on the Pressure switch. I am just saying I have only cound the one presure switch on the high pressure line running across the firewall. Jeremy

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Some times things come back from memory later than one would like it.

Call Volvo tech support. I did a year ago about the amount of freon needed on another truck. Then told me and were somewhat helpful on the subject.

But maybe they can send you the wiring schematic.

Do you have a local Volvo shop you could visit. It mite be good to get to know a parts person at the service desk that can help you with things like what you are dealing with.

 

Safe Travels, Vern

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