AC Clutch Issues

[deve05]

So now that I've gotten the top end of the 5.7 tbi redone and it no longer has a blown head gasket or a cooling system full of gunk, and now that it has a new radiator with fresh dex cool in it, I can move on to tackling some other issues the truck has since I bought it.

Next up on my list is to fix the AC, since Florida summers at 90+ with no AC is a no-no lol

I'm having a bit of an issue with the compressor clutch that I cant figure out. At some point I was damn near 100% sure it was the clutch. Here is what it does.

If I start the truck and turn on the AC, the clutch WILL NOT engage. I go under the hood and give the clutch an ever so light tap and it immediately engages. This made me think the clutch coil had gone weak. Now, once I tapped on the clutch it would stay engaged so long as the truck was on idle, the second I put it in gear and drove off it would disengage and would not come on unless I reved the engine a couple of times.

So I changed the clutch AND the pressure switch as a precaution and had the system evac and recharged by Firestone. The system blows cold and works great when the clutch is engaged, but even after replacing the clutch, its still doing the same thing. Anyone have any pointers as to what could be going on here? I will say the compressor does have a poorly done pigtail going to it with wires just meshed together and electrical tape around them instead of a but connector like its supposed to, could the coil be getting low voltage due to this and therefore not have enough power to keep the clutch engaged??

Thanks in advance for any help!

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[PlayingWithTBI]

could the coil be getting low voltage due to this and therefore not have enough power to keep the clutch engaged

Good question, check the voltage at that connector with the A/C on. Then run a hot wire directly from the battery to the compressor and see if it works better.

 

[deve05]

Good question, check the voltage at that connector with the A/C on. Then run a hot wire directly from the battery to the compressor and see if it works better.

Any idea what the voltage should be there and if a multimeter from one wire to the other would measure it or if I have to test with one lead on the multi meter to ground?

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[PlayingWithTBI]

I'd check to ground, then check across the pins, you may have a poor connection from the compressor to ground too. It should all be a minimum of 12vdc. Who knows, you may have a bad connection at the A/C relay.

 

[deve05]

I'd check to ground, then check across the pins, you may have a poor connection from the compressor to ground too. It should all be 12vdc. Who knows, you may have a bad connection at the A/C relay.

The compressor acts as its own ground by being bolted to the engine correct?

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[CorvairGeek]

The compressor acts as its own ground by being bolted to the engine correct?

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No, the clutch coil is isolated from the chassis. There is also (supposed to be) a diode between the two leads at the clutch. A missing diode can cause odd electrical issues when the clutch cycles off.

 

[deve05]

No, the clutch coil is isolated from the chassis. There is also (supposed to be) a diode between the two leads at the clutch. A missing diode can cause odd electrical issues when the clutch cycles off.

The diode is present, i verified this by pulling back the insulation on the pig tail. So if the coil is isolated then all thats left to do is check for proper 12 volts at the terminal, if voltage is correct. What would I be looking for next? Firestone recommended an AC compressor.... But i dont understand how the compressor can be bad if it freaking cools while the clutch is actually engaged.

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[PlayingWithTBI]

The diode is present

It may or may not be good though - disconnect the plug from the compressor and check with your ohm meter one way it should read 0 and with the leads reversed it should read OL

 

[deve05]

It may or may not be good though - disconnect the plug from the compressor and check with your ohm meter one way it should read 0 and with the leads reversed it should read OL

Okay, thanks for all the great pointers. Im hoping it's not the compressor after I sunk the money into the clutch. I guess i can always take it off and return since im within 30 days and the box is still at home.

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[Schurkey]

"I" would be testing VOLTAGE DROP, not voltage specifically.

This will require testing voltage drop on the + side, and also testing voltage drop on the - side.

Voltmeter + lead on battery +. Voltmeter - lead at the + side of the clutch coil. Turn on the A/C so the clutch is powered and (hopefully) engaged. Read the voltmeter: Should be UNDER half-a-volt. I'd really prefer 0.25 volts. Less is better.

Voltmeter - on battery -. Voltmeter + lead at the ground terminal of the clutch. Again, with the clutch powered, check the voltmeter. Should be under half-a-volt, less is better.