# jd 6715 ac compressor clutch not engageing



## seventyfourci (May 13, 2014)

The clutch is not kicking in has freon 70 psi on suction side. any ideas where to start with?


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## Tx Jim (Jun 30, 2014)

My guess system is low on charge of refrigerant. If it was my tractor I'd briefly hotwire the clutch wire & check high pressure psi.


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## seventyfourci (May 13, 2014)

Thanks Jim I will give that a shot. Do you have access to the high and low pressures and capacitiy?


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## Tx Jim (Jun 30, 2014)

AC high pressure is dependent on several factors such as cleanliness of exterior of cond/evap, AC filter, ambient temp & amount of refrigerant in system. If adding refrigerant to a system that's low I try to stay around 250- 275 psi on a 90+°F day


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## Gearclash (Nov 25, 2010)

Had a bad AC thermostat do that once. On a blue tractor so I can’t help where the thermostat might be. Probably in the cab near the cab blower.


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## Tx Jim (Jun 30, 2014)

Low pressure could cause low pressure switch to keep compressor clutch from engaging. Refrigerant pressures equalizes when compressor isn't operating. 70 psi X 2 = 140 psi combined which is low indicating low system charge pressure


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## Gearclash (Nov 25, 2010)

I would expect the AC to cycle on and off if the pressure was low. Since it isn’t coming on at all I suspect the thermostat. Seems to me 70 psi is about all I ever see on the low side with the pump not running.


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## Tx Jim (Jun 30, 2014)

My WAG is if one disconnects the switch in photo & briefly jumps connections on wiring harness that comp clutch will engage when AC blower is operating then if so high pressure can be briefly monitored. When I have gauges on my AC system & turn AC off gauges equalize at between 125 & 150 psi depending on refrigerant charge & ambient temperature.


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## dieselmike (Feb 24, 2018)

Disconnect low pressure switch and bypass with a paper clip.


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## seventyfourci (May 13, 2014)

Is the low pressure switch on the back of the cab by the drier on the 6715?


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## Tx Jim (Jun 30, 2014)

According to parts photo I posted earlier switch is very close to receiver/dryer


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## seventyfourci (May 13, 2014)

Probably high pressure switch being as it is located on the high pressure line. I jumped the clutch wire at the compressor the 6715 has a front mount battery one of my test leads has double alligator clips and more than long enough. Charged the system with 36 ounces 134a showing light frost at compressor. cleaned evaporator coils and dumped +/- 5 pounds of dirt out of cab filter and gave the filter a good cleaning and all is well. While working on AC found serious engine oil leak on the plug on top of the oil filter housing. Backed plug out o ring was split. I had a o ring kit in the truck so it was a quick fix. To those of you with 6715's or tractors powered with the same block this unit only has 2750 hours on it and appears to be easy hours by the looks of everything but the cab filter.


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## Tx Jim (Jun 30, 2014)

Congratulations on your repair
Notice switch is referred to as dual pressure which makes me think without access to a 6715 tech manual that this switch monitors both high & low pressures. Which makes sense because high pressure line becomes low pressure line when refrigerant charge gets low enough.


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## dvcochran (Oct 1, 2017)

seventyfourci said:


> The clutch is not kicking in has freon 70 psi on suction side. any ideas where to start with?


It is never turning on?
Does the compressor turn easily by hand?
Have you checked for voltage at the clutch connector? It should be intermittent but would be (mostly) continuous on a hot day when the tractor was first started. 
If there is voltage, check the clutch coil by looking for an open circuit with a DVM. If it is in spec (something 2-5 ohms resistance) then I would suspect the air gap is too wide. 
Just from setting, 70psi on the low side is not alarming but should be 25-30 (depending on ambient) when running and cycling. 
If all checks out, I would jump the connector to force the compressor to run. If the pressures and discharge air is all good, something is wrong on the temperature adjust/sensing or thermostatic side. There is almost always a low pressure switch, high pressure switch, and a switch of sorts in the cluster on new equipment.

In order, if the compressor turns freely by hand and there are no obvious issue with the controls, I typically check for voltage. Then put on a set of gauges and jump the connector and see if the compressor turns.


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## Tx Jim (Jun 30, 2014)

dvcochran
Evidently you didn't read post # 12 where 74ci stated he had AC producing light frost at compressor after cleaning/charging AC system.


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