AC Clutch Issues

[thinger2]

I believe 94 was the first year to use R134
Check the air gap.
Aftermarket clutches are never flat and true and the slightest adjustment can make a difference
Its a pain and worth swearing about

 

[thinger2]

I believe 94 was the first year to use R134
Check the air gap.
Aftermarket clutches are never flat and true and the slightest adjustment can make a difference
Its a pain and worth swearing about

 

[scott2093]

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.

Guess I'll hijack this. I've been starting to try to figure out why I'm only getting 11.3v at my ac clutch on my 93 k1500 Yukon... Sometimes it'll drop lower and I think it's causing my clutch to turn off . It was happening a lot before I found a loose connection at my alternator but it still happens every now and then and 11.3v seems it's teetering too low??

For some reason I have a .5v drop just from the ac pressure cycling switch to the compressor clutch. 11.8v at cycling switch...11.3 at clutch.

At the ecm, I'm getting 11.3v before it goes to the clutch and cycling switch which is making my head hurt thinking about it. Why would voltage be 11.7 at cycling switch and and 11.3 at clutch when the ecm has 11.3v. ?

I did see that the dk grn connection is direct from clutch to ecm with continuity check iirc.

I've got 13.4v coming into ac control unit and low blower relay. 12v at ac clutch relay...

Not sure what to look for next.... or if something is staring me in the face....
not looking forward to getting back to deciphering my ac circuit since it's different than what's in the manual...but I guess it's time again...

I saw a mention of using relays off the headlights? or something for the clutch but can't find the thread ? Maybe that's what I need?

 

[scott2093]

"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.

I've got 2.6V drop?
Reads14.4V until clutch cycles... Then 2.6V when it's on...

 

[Schurkey]

14.4 - 2.6 = 11.8 You have 11.8 volts of Voltage Drop (VD) not 2.6. 2.6 would be bad enough to indicate the wiring is insufficient.

Everyone knows VD is not good.

That wiring system has failed. Do you have voltage on the negative side?

 

[scott2093]

maybe my leads are wrong?
I mean, I get 11.3 to 11.7v when + of multimeter is at clutch +

and - of multimeter at battery - which seems like the 2.6v diiference from battery voltage?

But I'm following your lead so yeah, there's 14.2 v with meter + at battery+ and meter - at clutch+ when truck is running with ac on but clutch off,
and 2.6v when clutch is active....

no voltage from negative test....
I'll be home in a bit and will double check I'm not doing something wrong...
ac works afaik but maybe there is something really wrong
thanks

 

[scott2093]

yeah, there's 14.2 v with meter + at battery+ and meter - at clutch+ when truck is running with ac on but clutch off,
and 2.6v when clutch is active....
and...

Voltmeter - on battery -. Voltmeter + lead at the ground terminal of the clutch
.095 v

Checked pink/black to pcm and it gets 14v voltage....and stays even with ac on... why am I only getting 11.3v at PCM circuit 59 dk green to the cycling switch?

brown (50)wire to ac control unit gets battery voltage but drops to 12.6v when clutch cycles....

 

[scott2093]

So I just checked out of curiosity and, when the ac clutch is disconnected and I turn ac on, there's battery voltage, 14.2v at the clutch connector..
When the clutch is connected and getting the ac on signal, it's 11.4v??

Clutch resistance is fine.....

Why so much drop? Alternator "voltage" output stays rock steady regardless..

 

[Schurkey]

So I just checked out of curiosity and, when the ac clutch is disconnected and I turn ac on, there's battery voltage, 14.2v at the clutch connector..
When the clutch is connected and getting the ac on signal, it's 11.4v??

Clutch resistance is fine.....

Why so much drop? Alternator "voltage" output stays rock steady regardless..

Common as dirt.

You're seeing the result of undersized or deteriorated wire, and/or corroded connections.

When there's no current flow, you see system voltage even though the wire harness has problems.

When there's current flow, the resistance in the harness drops the voltage.

This is why voltage-drop testing of various electrical components--including starter, alternator, fuel pump, HVAC motor, headlights, your A/C compressor clutch, etc. have to be done with the components connected and WORKING. You need the appropriate current flow (amperage) in order to assess the resistance in the circuit.

You have some options: You can trace the wire harness back to the battery, and replace/repair whatever sections are providing excess voltage drop; or you can use the existing harness to trigger a relay connected to a power source (battery, alternator, some other junction block) using fresh wire of appropriate gauge, so that the A/C clutch gets proper voltage and current (amperage).

 

[scott2093]

Thanks!
Makes complete sense now.

I know for certain all the terminal voltages from ecm check out except for the a/c request circuit. DK Grn 59... It is only 11v and change.
It's been a little since I had the ac controller out to check circuit 59 there.....need to do that.

Any chance I could take a , like idk, 500mA dc wall wart and inject the disconnected line to see if there's a drop along it?...
I saw this mentioned a few days ago but I'm guessing it may not be good for wiring that's intact?

ECT3000B

shop.powerprobe.com

I just feel like I get lost in my thought process when trying to narrow this down... Slowly but surely....
Just found some creamy transmission fluid when disconnecting my wife's lines from her 4runner's radiator getting ready to do the water pump/timing belt dance....... so it'll be that much more slow it's looking like....


ok...
Checked circuit 59 at ac controller.... strange....
11.2v with key on..... turn ac on it's 12.3....put blower on high, 12.7
turn off key, it drops to 11.2v then slowly goes up to 11.5v, drops down to 1.5v then slowly starts bleeding down....
Resistor in controller bleeding off voltage?
Why the jump in voltage when ac on.....still doesn't explain drop at pcm and to clutch..... I'll look more...weird.....there any caps in that thing that could be funky and causing some stuff? or does this sound normal?

Power to ac controller red is 14.2 with truck running....so good there.....