[Cloud9...68]

Wow, some serious A/C knowledge here. I'll know where to turn if I ever have problems with mine...

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[rl968]

OK, here's an update...and of course more questions.



Using my MM, I tested the black/red wire coming off the switch by putting one probe on the contact and the other on the engine (I used the front hoist point). The fuse immediately blew, fans went off and AC dash switch light went off, but not sure why that happened. I set my MM to DC10a to test...is this the correct setting? I put a pic of my meter below so if I should set it somewhere else, please let me know. Definite novice with a MM. I replaced the fuse and all was working again. Positively, I guess this means I do have power at that point.on the switch, which eliminates a few things, including the AC relay and control unit, and I think narrows it down to a break in the black wire from the switch to the compressor, the compressor/clutch is bad, or the pressure switch is bad.



To test the compressor clutch, can I run a line from the positive terminal on the battery to the terminal on the compressor where the black line is connected and then start the car to see if the clutch engages? Any risks here? I don't have automotive wire, so can I use 14g household wire (the kind you would find in your outlets and switches?) Again, have some sympathy if this is a stupid question.



Thanks for all the help, I feel just a little closer to getting to the problem.







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[Paul W]

You are getting close....but no cigar....few pointers.



Change the red lead on the multimeter to the other terminal on right hand side of the meter as you look at it....leave it there 99.9% of the time. With it plugged into the DC 10 Amp port, it is set up to measure current, not voltage or resistance. What happened was that you provided a direct short to ground with the meter set up that way, it has a small "shunt" inside the meter that is used to measure current by measuring the voltage drop across the shunt, which is a very, very low voltage drop.



Anyway, to test the black/red wire, which would be 12 VDC to the compressor, do the following:



Move the multimeter lead to the right hand side.



Set the multimeter to DCV (DC volts), on the "20" scale, which is 20 VDC total scale, you are measuring 12 VDC, so this is perfect. This is the 11 o'clock position on the dial. Start the car with the AC on (replace your fuse) and then put the red multimeter lead on the red/black connector wire, and the black on the engine, and you will read 12 VDC.



You have basically verified that the voltage was present by causing a direct short to ground which tripped the fuse. So you know it's somewhere from the low pressure switch, the wiring from there, the compressor clutch, or the compressor ground. It doesn't matter which lead on the multimeter goes to ground or the connection, it will just read +12 VDC or - 12 VDC, switch them around and you'll see that on the readout.



So the next step would be to:



With the car off, measure RESISTANCE or the clutch wiring/coil.

• Leave the leads in the same configuration, red lead on the right hand side of the meter when looking at it
  
  
• This is a DEENERGIZED test, never test resistance on an energized circuit (with the connector pulled off, the black wire half is deenergized, with the car off, the whole circuit is deenergized downstream of the compressor relay.)
  
  
• Set the multimeter to the 200 Ohm scale (7 o'clock position)
  
  
• Test the multimeter by touching the two leads together, the meter should read 1 ohm or less. This verifies that the meter is good.
  
  
• Put one lead on the black wire (pin 1 of the connector) and the other on the engine block. You are seeing if there is continuity (no open wires), if everything is good, you will find a resistance of a few ohms to maybe 15 ohms.
  
  
• If you find that you have an open circuit (meter will read the same as when it's connected to nothing), then the problem is in the wiring going from the connector to the compressor, the compressor clutch or the ground of the compressor.
  
  
• If you have a good resistance reading, then read the resistance across Pin 1-4 of the low pressure switch, it should be closed if the system is charged. If it's open, the compressor clutch will never energize.
  
  

The other test as you mention above, is to take a piece of wire and connect it to Pin 1 of the connector (black wire) and then touch it to the + battery post. It should pick up the compressor clutch. However, if you have an open circuit, it WILL NOT pick up the compressor clutch because no current can flow. There should only be a small spark when you touch it, and then it would pick up. If a HUGE spark, just lift the wire off, as there is no fused protection in this case.





14 gage single conductor home wire will work just fine.



Do a couple more tests and report back.

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[rl968]

Thanks Paul. I had my meter set up different when I tested for continuity the other day so it is confirmed that the circuit between the black wire on the connector to the compressor is not getting power and I need to find the break.



Can I run a line from the + terminal on the battery to where the black wire connects on the compressor itself and then start the car to see if the clutch engages? Id also want to verify the system had a charge so would i need to plug the pressure switch back in and then just operate the dash controls To see if cold air comes in.



I notice that the black wire coming off the compressor has a taped connection in one section and has a connector connection a few inches away. I wonder if one or both of those connections might be the issue??

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[Paul W]

Most electrical issues are with a connection. The taped connection would be suspect to me.



No need to turn the car on to jump the battery wire to the black wire, it's unswitched power, you will hear the clutch "click" (pick up) if the circuit is good (which you said it was open in a previous post), and if there is no spark, no current.



If that was the case, and you verify it is open with a continuity check with the multimeter, then untape the taped section, see what you find and perform a continuity test from there. If you have continuity, then do the 12 VDC jumper test to that point, if you hear the clutch pick up, you found your problem. If that connection is bad, then all you have to do is to make up a new connection between the two and you'll be in business.

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[DaveN]

You will probably have to replace the fuse in your MM as well, probably open now <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />

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[rl968]

MM is fine.



I have this connector below and it is not the issue as I got continuity from the switch connector (Black wire) down through both sides of this connector. I now need to get under the car, remove the bat wing and check the compressor connection and the compressor itself. I feel like I've narrowed it down pretty good. The compressor is a denso reman unit that I just got so I assume it's good, but maybe not..more testing this weekend when I have time to get under the car.



I also tested the pressure switch for continuity through pins 1 and 4 on the switch, the ones that would connect to the black and black/red wire, and did NOT get continuity so I think this tells me that the switch is bad.







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[MB968]

As Paul (great info/advice) mentions above, I'd check the clutch/coil for proper resistance of the coil. As described, it will also check the grounding of the coil. I'd do these next since it is easy to do them from the plug you show in the pic (at least I assume that is the one that the compressor wire plugs into). If you get good numbers here then you can move onto getting underneath.

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[Paul W]

If you did not get continuity through the switch Pins 1-4, the next thing I would do is just jump 12 VDC to Pin 1 (black wire) and see if the clutch picks up. If you do not have continuity, then you either have a bad switch, or no or inadequate R-134A charge in the system.



You are almost there!

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[rl968]

I still need to make sure I have continuity all the way to the terminal on the compressor where the black wire connects. Havent done that yet. Then I can jumper from battery through pin 1 and hope the clutch engages.



Can I remove the switch and test continuity? Or will the fact that there is no pressure behind it keep the switch open? Wish I had some AC equipment to test system pressure.

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[Paul W]

There is no need to remove the switch if you can get your multimeter leads on the pins.

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[Paul W]

I just ran across this page for a rebuilt compressor clutch while searching for something else, it appears that there is both a power supply and ground wire coming out of it.



http://www.klaindust...h/ac-clutch.htm



So when you get under the car, see where the clutch wire grounds out and make sure it has a good ground. The clutch coil is the black thing in the picture, and it is many turns of fine wire inside.

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[rl968]

I just tried to jumper from the switch to the battery and got nothing. Not good. Perhaps I need to ground the compressor with a line from the negative battery terminal to the compressor and then try again?



I'm going to have to get under there and check the connections better. It's pretty tight fit.

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[Paul W]

So you know where your problem is....downstream of the low pressure switch (even though you said it was open circuited, maybe you just didn't test it right).



Next step is to get under the car and inspect the wiring. Considering this all happened after replacing the compressor, I would not be surprised at all if you have a loose or wire that is not connected.

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[rl968]

im concerned compressor is bad. We'll see.

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[rl968]

Got under the car today, and not the best news.



First, access to the wires is not possible without removing the compressor, pretty crappy design.



Second, the compressor is grounded to itself as there is a wire on the compressor where one end goes to a lug on the top of the compressor and the other goes on another lug over where the hot wire is connected (they are not touching as there is a hot lug and ground lug). I get continuity when I put one probe on the ground screw lug and the other on the front of the compressor. Don't get continuity if I touch it anywhere else...not sure if this is an issue .



Third, it looks like there is some kind of connector on the power wire just before the connector on the compressor and it looks a little burnt (see pic), but it's very hard to see. There is not enough access to remove the wires with the compressor connected so I am going to have to have it removed and that I can't really do myself. There is a good AC repair shop near me so I'll see what they have to say. Very depressing I can't fix this, but at least I appear to have isolated the problem all the way to the compressor.







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[Paul W]

If it's the connector that's bad....at least it's good news that the clutch isn't bad......too bad that you had this repaired and it never worked. Hopefully performing a proper repair to the wire will get it working again!



And think what you learned about troubleshooting it!

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[tamathumper]

Is that a crappy crimp-on connector?!

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[rl968]

Yeah, I learned a lot from this, including how to read a wiring diagram and use my MM better, thanks for all the help. Just don't like having to fix things twice.



Can't tell what kind of connector it is, or even if its a connector, very hard to see it, but it does look different from the black wire. Its possible i could pull it apart, but id never get it back together without pulling the compressor. I took that shot blind as its on the top of the compressor.



Anyone ever take their compressor off? Is there enough slack in the lines to manipulate it and drop it down a bit? Seems you just loosen the tensioner, slide belt off and remove the mounting bolts. But howmuch slack will that get me?

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[MB968]

[quote name='rl968' timestamp='1376760162' post='147458']

Anyone ever take their compressor off? Is there enough slack in the lines to manipulate it and drop it down a bit? Seems you just loosen the tensioner, slide belt off and remove the mounting bolts. But howmuch slack will that get me?

[/quote]

Don't quote me on this, but when I pulled the engine (out the bottom), I don't recall having any issue with just moving the A/C compressor out of the way. So, I believe you'd end up with more room to work on it.

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