EverydayDiesel

Of course I pulled a vacuum on the system with a robinair 5cfm pump for 45 minutes and it held the same pressure for an additional 45 minutes. I cant get any more r134 in until the compressor comes on. The OEM pump comes with all the pag20 oil needed.




Im thinking the wires at the pump harness are crossed. (All though I have checked and checked again, the solid black goes to solid black, and the stripe goes to stripe) What happens if I switch them, the diode will stop it if theres voltage going the wrong direction right? I dont see any harm in reversing the wires to see? Anyone see anything wrong with that?

I will be checking the continuity as soon as I get a new battery for my fluke.

vzdude

Can you follow the wires to see which one is grounded on the compressor? MANY times the aftermarket clutches arent color coded to the factory wiring. Heck......I would just swap the wires with an aliigator clip for a second or two! What's another fuse!?!?!?

bent valves

I am holding a clutch coil in my hand and read a resistance of 3.2 ohms on the coil. Neither of the two coil wires should measure low resistance to ground with the connector disconnected. Since the coil is floating from ground it should not matter which wire sees 12 volts. Connecting it either way should create the magnetic field needed to engage the clutch. Start your troubleshooting by measuring the resistance with your meter.

EverydayDiesel

I swapped them and saw no difference. The fuse blew the same way.

The coil on the new pump reads 0.3 ohms of resistance.
The old coil reads 3.6 ohms.

Continuity in my mind is 0 ohms of resistance...anything else (or O.L. on my fluke) isnt. Neither of the leads coming off the compressor (with the harness disconnected of course) read zero ohms. Neither of them read 0 against ground on the battery or directly on the bare metal side of the pump.

Is it more likely that im breaking the coils? or is it more likely that I got two in a row that are bad? Should I make them give me another one and test it out over the counter this time?

vzdude

.3 ohms is about as close to a direct short as you can get. Do either of the wires have resistance to the body of the compressor? Will the compressor turn by hand? 3.6 ohms is pretty small as well, though. It sounds like a bad clutch coil for some reason......I can't imagine having 2 in a row, but the previous one wouldn't engage at all right? Oh yeah.....you had the whole terminal issue.....take this one back to the dealer, or maybe ask them over the phone if they can read the clutch coil resistance on the one that they warrantied for you. If it is o.k. then maybe you can get them to swap them. The first replacement may have been fine. I'll see if I can get the spec on the clutch coil for ya.

vzdude

DIAGNOSIS AND TESTING - A/C COMPRESSOR CLUTCH COIL
For circuit descriptions and diagrams, (Refer to Appropriate Wiring Information). The battery must be fully-charged before performing the following tests. Refer to Battery for more information.

Connect an ammeter (0 to 10 ampere scale) in series with the clutch coil terminal. Use a voltmeter (0 to 20 volt scale) with clip-type leads for measuring the voltage across the battery and the compressor clutch coil.
With the a/c heater mode control switch in any A/C mode, and the blower motor switch in the lowest speed position, start the engine and run it at normal idle.
The compressor clutch coil voltage should read within 0.2 volts of the battery voltage. If there is voltage at the clutch coil, but the reading is not within 0.2 volts of the battery voltage, test the clutch coil feed circuit for excessive voltage drop and repair as required. If there is no voltage reading at the clutch coil, use a DRB III® scan tool and (Refer to Appropriate Diagnostic Information) for testing of the compressor clutch circuit. The following components must be checked and repaired as required before you can complete testing of the clutch coil:
Fuses in the junction block and the Power Distribution Center (PDC)
A/C Heater mode control switch
Compressor clutch relay
A/C High Pressure Switch
A/C Low Pressure Switch
Powertrain Control Module (PCM).
The compressor clutch coil is acceptable if the current draw measured at the clutch coil is 2.0 to 3.9 amperes with the electrical system voltage at 11.5 to 12.5 volts. This should only be checked with the work area temperature at 21° C (70° F). If system voltage is more than 12.5 volts, add electrical loads by turning on electrical accessories until the system voltage drops below 12.5 volts.
If the clutch coil current reading is four amperes or more, the coil is shorted and should be replaced.
If the clutch coil current reading is zero, the coil is open and should be replaced.

Busboy

As the compressors are heavy installing them in hard to reach areas is difficult. I would sometimes see installers squish the wires between an edge of the compressor mount (which is sharp) and part of the engine block. This is enough to cut the wire but not the insulation, it just flattens the insulation so it gives the appearance of still being OK. It's hard to think you did it but take a look. Out of around 800 compressors installs a season in the shop we might see one sometimes two with a bad coil the rest were pinched wires by the installer.

Not to say that yours weren't bad coils or the wire was shorted at the factory and not tested, the diesel compressor is very type specific and maybe a new assembler at the factory.

EverydayDiesel

I just checked again. This is not the case, the way they route the wire over the top of the compressor, and how tight it is, its impossible to short the wire between the bracket and the pump. The wire is untouched and out in the open.

EverydayDiesel

The meter shows O.L. when I put either pump terminal on one end and the metal body to the other end. So that means that the pump is not shorted out to the outer casing at least.

I am able to turn the center of the pump by hand either way. I could also do that with the old pump.

I remember measuring the old pump right before I took it back and it read 0.3 ohms across the terminal just like this one does. 0.3 might as well be no resistance as you said earlier, a dead short, which explains why Im popping fuses only when i hook the pump up .

duner

3.6 ohms resistance at 14 vdc would draw 3.88 amps. .3 ohms resistance at 14 vdc would draw 46.66 amps.

bandit408

First off which fuse are you blowing? The one in the juction block in the cab or the one on the power distibution center under the hood?

bandit408

That single fuse in the junction block in the cab controls not only the ac clutch but also the fuel heater, the central timer module, the overhead console, and the auto day/night rearview mirror.

vzdude

Re read the posts.....the fuse will only blow when the compressor is plugged in.

EverydayDiesel

its the a/c clutch relay switch outside next to the battery.
its the 10amp fuse on the left second one from the bottom

vzdude is right, it only blows when the compressor is plugged in.
It blew with the first new pump, it blew with the second new pump but it works just fine when you hook up my old pump. At this point im going to ask for a 3rd tomorrow.

I mean what other choice do I have. The answer is obvious right? or is it just me that thinks so?

vzdude

Sure sounds like the issue to me.......hate to say it, but take a DVOM with you when you get the new one this time. The above resistances should be pretty close.