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Discussion Starter #1
hi my sons Dakota's a/c clutch has stopped working, first he noticed an increase in fuel economy then noticed that he couldn't here the clutch engauge anymore, I did a few simple checks, the fuses are all fine, I swapped the clutch relay with the same one used in the horn, but no difference, there are two connections going to the a/c compressor, I unplugged and checked them both and they seemed fine although one had been repaired before in the wire just before the connector with an electrical butt connector but it seemed fine, the compressor pulley spins fine with no growling noises but the clutch wont engauge in either a/c mode or defrost as it did before, any ideas or common problems or maybe some one knows what wires going to the compressor should have voltage, I have a Haynes manual but havn't gotton that far yet as I have a couple other projects I am still deep in, Thanks
 

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Take the connector apart that powers the clutch. Take a voltmeter and see if there is 12v present when the clutch is supposed to engage. If yes, do a resistance test on the wires going to the clutch. If no ohms, an open circuit your clutch is defective. If you have no voltage going to the clutch plug, check the A/C relay by plugging another relay known to be good. This should isolate the fault.
 

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Probably enough freon has leaked out that the low-pressure cutoff switch will not allow the compressor to engage. To check this, unplug this switch where the A/C lines go into the firewall (hooded 2-wire plug on the side of the switch) and jumper the plug with a paper clip, and then start the engine and BRIEFLY engage the A/C. If the clutch engages, either you are low on freon (very likely) or the switch is bad. Don't run it this way more than about 20 seconds or so, so as not to damage the compressor.
 

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Discussion Starter #4
ok thanks guys, those are both good places to start, Dak4x4, the resistance test on the wires you mentioned is that between the two wires or each wire to ground at the clutch?, as for the relay that was one of the first things I tried, Bob, I thought when the system was low on freon,(because I did think about that), that the clutch would engauge madly back and forth?
 

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There's only a very narrow threshold where the clutch cycles that rapidly. Below that, it won't even turn on.

For dak4x4's test, measure resistance across the contacts at the compressor clutch's electrical plug, between the two wires that go to the clutch from that connector. If it's either zero or infinity, the clutch winding is bad. A value somewhere between, say, 3 ohms and 10 ohms or so would be good.
 

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Discussion Starter #6
well it seems there is no voltage at the connector, I swapped the relay with the horn one and no power still, Bob, I cant find the connector at the firewall although there is a wire or two that goes in a loom to somewhere in behind the washer bottle on the firewall, could that be it?
 

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When you find there is no voltage, are you measuring the plug to the compressor (unplugged, of course, there is no voltage there) or the other half, leading back to the relay? Did you measure resistance across the clutch winding?

If the low pressure cutoff switch does not allow the A/C to turn on, then of course the clutch relay won't close and there will be no voltage to the compressor. You should still check into whether there is a freon leak. You can buy a gauge at most auto parts stores. It will be an R134a gauge, which has a quick-connect fitting, and not the old Schrader screw-on fitting from the R12 days.
 

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Discussion Starter #8
I of course measured the voltage on the half going back in the harness, not the pigtail on the clutch, and yes I measured for resistance across the pigtail going to the clutch, nothing, all zero
 

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Discussion Starter #9
ok according to my manual it says to jumper the harness at the accumulator where the pressure switch is, I did this and still no clutch, it then mentions testing voltage at the relay box at terminal 30 and 86 I have not done this yet, its getting dark and my garage is full of projects so back at it later this week, any more ideas?
 

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You should not get zero ohms on the clutch winding. It should be something like several ohms. I'll measure the clutches in my car and truck as soon as weather allows (big snowstorm right now).
 

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Discussion Starter #12
hey Bob the whether up here is getting warm, how about where you are? did yo get a chance to check that ohms reading yet or are you still shoveling?, lol, thanks
 

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I'll check it tomorrow, got caught up in repairs of my own.
 

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Discussion Starter #14
yep I know what thats like I am still finishing the trans swap on my sons truck in the garage with parts delays this thing has been apart since January, some times its hard to find time to squeek the small jobs in, take your time but I appreciate the help.
 

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Came down with a bad cold Wed night, still have congestion, cough and fever.

The compressor on my Dakota 3.9L V-6 measures 3.0 ohms across the winding. It starts at 4.3 ohms, within a few seconds it drops and stabilizes to 3.0. On my Daytona, it starts at 4.3 ohms and stabilizes at 2.6 ohms. I'm guessing that the meter is charging up the winding.
 

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Discussion Starter #16
ok thanks that gives me a base line I will check it against my sons tonight after he gets home from work or tomorrow
 
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