I have recently replaced these items with dodge parts.
Compressor, drier (with brand new low pressure switch), liquid line, condenser.

I pull the system into -28 vacuum with a robinair 5cfm pump for 45 minutes with the pump running. Another 45 minutes with all the valves shut making sure it holds pressure and it does so I do not have a leak.

Then I go to add my first can of refrigerant to the low side. The can gets about half - 3/4 empty and my gauges read 70psi on both sides. I go to start the engine and then turn the a/c on max a/c but the compressor will not turn.

All the fuses check good.
I swapped the relay out.
I shorted out the low pressure switch/harness to fool the circuit but the compressor still does not engage.

Im stumped what can I do?

 

Check for power and ground at the compressor with the engine running and controls on. May have too large of an air gap on the new compressor. At least narrow it down to power or ground issue.

 

I have ground on the black/yellow wire
I have a switched +12v on the solid black wire. (+12 volts is there when you turn the a/c switch inside the cab)

I guess the new compressor is bad? or at least the clutch?

 

Sure sounds like it! Did you use a multimeter or a test light? A test light can help show a degraded connection or a poor ground. I made a huge test light out of a headlamp ( old H6054? glass style) to make sure that the wiring will handle a load. A multimeter will give good voltage readings because there isn't a load on it. But again.....sounds like a bad clutch or improper air gap setting.

 

I used a fluke meter....14.01 volts was the reading.
I need to build one of those test lights soon.

I dont understand what you mean by air gap setting?
I havent touched anything on the compressor. i just took the bolt and the cover that covers the two ports on the back, bolted it to the truck and then hooked the lines up. Was I suppose to adjust something ?

 

No.....the air gap gets adjusted when it is put together. Check the compressor itself and see if there is resistance thru the clutch coil. Either way, they should warranty it.

 

Did you put any oil in the system? Is the clutch trying to engage at all? You may just havea bad clutch and that can be removed off of the front of the compressor without discharging the system.

If the compressor gets exchanged, ask for 3 cans of freon to replace what your going to have to dump. Heck, ask the dealer if they'd recover the freon for you on thier dime to keep from venting it. It'll only take about 5 minutes. Tell them it will be the Green thing to do.

 

If you have power and ground at the compressor then inspect VERY closely the power wire going into the clutch coil. I have seen many that get damaged internally, if you find a flat spot on the wire that is probably it. Otherwise its a bad clutch coil but 9 times out of 10 its the wire...... good luck.

You can confirm the break by sticking a test lamp on either side of the damage.

 

Well I replaced the compressor today with a brand new one from dodge.

The compressor still will not come on. I have 14 volts on the connector right before the compressor. What would the next step be to figuring out this headache? Do I need to build a test light like you were saying? Is there anything else that would cause this other then the wire not being able to carry the amperage?

Can someone explain where the wires are going so I know where to trace if thats the next step. This is very flustering, and thanks for helping again.

 

I found out that the connector from the truck was bad. When you would plug in the compressor harness it would push the terminals out of the connector. Problem fixed...but now.......

NOW IM BLOWING FUSES!!!!!!!!
Its fine until I turn on the compressor and thats when the 10amp fuse pops.

If I put the fuse in with the truck off I get 12v on both sides of the fuse.
If I turn on the truck with cab a/c selector on OFF then the fuse is still good.
The second I turn on the compressor...the fuse pops.

Any ideas on where to check? Its obvious I have to follow the solid black wire (+12 volts) but where does it go and how far should I trace it?

 

I would unplug compressor clutch and see if fuse still pops. If it does you have short to ground on that wire. If not could be bad clutch coil or short at the clutch wire.

 

No way I got two bad compressors in a row from dodge. They even have different part numbers (they said it was a revision). My old pump ends with A05 the first new pump ended in A08 and this new pump I got today ends in A07

I unplugged the compressor like you said. started the truck, turned the a/c on and the fuse was still good.

I took some alligator clips and hooked up my old pump (just laying on the ground) the clutch locked up like it is suppose to. (but this is with no belt load on the pump remember it was just laying on the ground)

Then I took the new compressor and hooked it up, started the truck and turned it on and the fuse blew immediately.

I havent done anything to the pump except bolt it up, hook the lines up and plug in the harness. Do I have to prime or turn it a few times to get it to work? Maybe the load is too much since it is new and thats why its popping fuses?

 

Are you sure the wires are in the correct side of the connector? Test the wires coming out of the compressor. One should have continuity to ground. Make sure that it is not getting connected to the power side of the truck connector. IIRC, the compressors from Dodge have to have the original wiring re installed........could have been hooked up backwards!

 

what happens if i switch the wires around?
Im matching the solid on the pump to solid on the wiring harness. (i also match the stripe on the pump to stripe from the harness)

any damage if i reverse polarity on the pump?


edit: i remember there was talk about a diode on this pump. its possible that it is keeping it from getting any power because the polarity is switched. Anything negative might come from reversing the wires?

 

Have you pulled a vacuum on the ac system and installed the proper amount of freon and oil ?