Automotive Air Conditioning Information Forum (Archives)

marinermcv on Fri October 01, 2010 7:23 PM

Year: 2000
Make: Dodge
Model: Ram
Engine Size: Cummins
Refrigerant Type: R-134A
Country of Origin: United States

Have a Dodge with a 2-wire pigtail on the compressor/clutch what wire to I need to put 12 volt + to get it to kick in.

TRB on Fri October 01, 2010 9:45 PM

This vehicle is not one you really want to be bypassing or jumping to power the clutch. Clutch relay pressure sensors all send power to the clutch.

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GM Tech on Fri October 01, 2010 9:54 PM

Easiest to just jumper the relay in the relay center...

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

iceman2555 on Fri October 01, 2010 10:02 PM

This compressor also has a 'built in' diode in the clutch. Be very careful.....wiring must be specific. Agreement....with not 'jumping' the clutch....have seen some serious problems arising from this procedure.
Why not diagnosis the problem and make the repairs. A diagnostic flow chart and a good DVM and one should be able to located and repair (properly) the fault.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

ice-n-tropics on Sat October 02, 2010 1:43 PM

iceman is spot on.
A microsecond of reverse polarity will blow the 1000 volt diode imbedded in the clutch wiring harness a few inches from the clutch. The diode is used on RAMs to prevent negative voltage spikes from the clutch coil collapsing magnetic field from damaging vehicle electronics. The faster a clutch disengagement mechanism (relay or thermostat) breaks the current, the greater the negative voltage spike which enters the vehicle wiring. Over 500 volts negative is possible when reading a oscilloscope.
Hint: Whenever doing welding on a vehicle, be sure the battery is totally disconnected to prevent blowing diodes.
hotrodac

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

bohica2xo on Sat October 02, 2010 2:12 PM

"Jumper wires. Selling replacement compressors and added labor since 1955"

Every time I see someone post "I jumpered xyz to get it to 'pull in' refrigerant" I just smile. I used to try to discourage that, but like 134a conversions people will do it anyway. So now I just grin, and think of the compressor running in vacuum with no oil, and no mass flow of refrigerant to carry away the heat. For an hour or more while they work out the real issue with not getting refrigerant in to the system. Mmmmm Tasty. fried / ground compressor.

A jumper wire is just fine in a two terminal pressure switch connector for a few seconds to see if the switch is bad - but a DVM would still be a better choice.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Chick on Sun October 03, 2010 12:05 AM

I "believe" that is an O tube system, so "if" you jump anything jump the cycling switch, this way you get 12 volts to the compressor and it's going thru the right wire.. But we don't know why you are jumping anything, and that would be good to know, as we may have a better way for you...just sayin....

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose