No power to AC clutch?

[miketyler 15]

For some reason, my clutch no longer engages on my AC. I checked the clutch itself and all is good there. I checked the binary pressure switch and it is made and should allow power to clutch.

 

I am not getting power to the green wire coming out of the firewall that supplys power to AC. In fact, it appears to be grounded. Not sure if this is normal. I checked fuse and am getting power there so I guess that only leaves the fan switch and the de-ice switch?

 

How likely is failure of either of these?

[Stevewr54 12]

Aftermarket or OE system? Steve

[miketyler 15]

Aftermarket Sanden pump. With the exception of the binary switch low pressure circuit I added, all the rest is OEM. However I am not getting power at the firewall.

[LindenBruce 27]

The green wire should NOT be grounded. If you are reading continuity to ground it is shorted somewhere under the dash. Begin tracing it out. B.

[miketyler 15]

Man, I hate taking things back apart once I have them put together but thats the fun of it eh? So with key on, it looks like power starts at the 30a fuse then goes to the fan switch and supplys power to the AC selector. From there, flows thru the de-ice switch to the green wire that runs thru the firewall and goes to the clutch.

 

The de-ice switch is low hanging fruit. On an AC car you can simply disconnect the glove box lanyard and let the glove box door hang. You can then reach up to pull wires from it. Of course I'm not getting power to either of those with key on, and fan switch and AC selector on. I guess the next thing is pulling the radio bezel to get behind the AC panel.

Edited April 11, 2014 by miketyler

[danno 128]

Don't bother pulling off the radio bezel yet, try some more things. Where is the low pressure switch you added? Is it between the de-ice and compressor?

 

The problem that used to happen was that the compressor clutch take a lot of power. That is why there is a 30 amp fuse, it is a lot of current going through the switches and wires. When you are checking for voltage, I will bet you disconnect the plug, and insert the voltmeter in the connection. You must make the voltage tests with the whole compressor connected.

 

You can often measure one voltage with a electrical load on the system ( the compressor) and a different voltage with no load on the system ( compressor disconnected). One way to do this is to use a voltmeter probe with a very small, very sharp, point on it. Then just stick it into the side of any wire so the probe tip hits the wires.

 

I will bet you have a high resistance in the fuse or fuse block. It measures 12 volts when the compressor is disconnected, and when you connect it and turn it on, the voltage drops to zero. I know about this because I have seen it myself.

[miketyler 15]

I dont think I am getting power on the engine side of the firewall. Will confirm tonight. Not looking forward to pulling bezel and radio :(

Edited April 12, 2014 by miketyler

[miketyler 15]

I am done helping with landscaping projects so I hope to look at this again today. I was not getting any voltage reading from the line coming out of the firewall so once I confirm that my next steps would be behind the radio bezel.

[miketyler 15]

I think I found the problem. Its the small micro-switch (Klixxon?)on the AC control lever. It was intermittent and I was able to probe the contacts and see the dropped contact on the outgoing terminal.

 

This looks like a common micro-switch I have seen in aircraft in my aviation days. Best to replace or can you use contact cleaner on these?

[Wycked69 20]

You can get those snap action switches in McMaster Carr pretty cheap

[danno 128]

I might even have one I can give you, let me check.

[miketyler 15]

Ok, I got it out and indeed its a Cherry Electric switch. Klixxon makes the aircraft circuit breakers I think? Regardless, the good old boys at Classic Auto Air always there ready to help and want $25 for a new one + $7 shipping. Love those guys. It wouldn't surprise me if you can buy 10 of them from Mouser or other electronics supply for that.

Edited April 15, 2014 by miketyler

[miketyler 15]

And the McMaster-Carr app for iPad rocks.

 

Just saying....

[danno 128]

Can you post a picture of it? I think I have one, but I am not sure what it looks like. My car is still in winter storage, and I cannot look at it now.

[miketyler 15]

Here it is. Its a Cherry Electric E34

Edited April 16, 2014 by miketyler

[miketyler 15]

I think this one should work. Its 15a and 125/250v AC rated. thoughts?

 

http://www.ebay.com/itm/NEW-E-SWITCH-ARCADE-MICROSWITCH-FOR-PUSHBUTTON-CHERRY-/400262597694?pt=LH_DefaultDomain_0&hash=item5d31828c3e

[miketyler 15]

I changed my mind and figured these were cheap knock-offs of the original. I ordered a couple of Cherry Electric E34 series this morning from Mouser. They are in my neighborhood only a few miles away. $13 shipped

Edited April 16, 2014 by miketyler

[danno 128]

The Mouser parts should work perfect. I order things from them all the time. I have a switch that could have worked for you, but it sounds like you already have it taken care of. $13 is reasonable, beats the price from the Classic Auto Air people. You probably do not need the AC now, but soon you will. Goodl luck with it!