Activate AC clutch

[CeaSaR]

Hi gang,

I have a '95 Dodge Intrepid that has developed a problem with the AC, it
quit working. I actually noticed this during the cooler months when I
smelled that awful stench of failed electronics. Yes, the fan still works,
heat, lights etc., but no engagement of the clutch. What I would like to do
is verify that the clutch still works by temporarily jumping the terminals to
see if it will engage. Unfortunately, not much is posted on the web on
testing an automotive AC clutch. Does anyone have any information on
this or ideas? I would hate to jump in and fry something. Any help would
be greatly appreciated.

CeaSaR

[gerty]

The A/C clutch is just a 12vdc solenoid, putting 12 volts to it will cause it to engage. When you energize it you can see/hear it move. On GM products one terminal is grounded right at the compressor, not sure about Dodge but should be the same. Some have a diode across the terminals for reverse emf, you might want to check to see that's ok. Had a friend who used a 555 circuit to cycle the clutch on/off, he smoked his controls but still used it by varying the duty cycle, crude but it worked..

edit: the engine doesn't have to be running to do this.

[CeaSaR]

Thanks Gerty,

Shouldn't the blades be polarized? As in one is larger than the other for
pos/neg? I'll see if I can figure that out, but not until the temp outside
drops a bit. 98+ degrees is to hot to work out in the sun for me.

If that works, does anyone have a 555 timer circuit that would run at 50%
duty cycle, 2 min on, 2 min off, driving a suitable relay, with a second
momentary switch on the reset to temporarily override the "off" cycle for
an extra boost, say, at the beginning when the car interior is hot and it
needs to run extra? I would wire into a switched fuse and have an ON/OFF
switch also. The last request is that the parts be available at Radio Shack,
as I need to put it together fairly quick.

Thanks again,

CeaSaR

[gerty]

There should be a 2 terminal plug on the compressor, one wire from that plug should go straight to ground , probably on the compressor bracket itself. The other wire (pos) should go to your temp control, that's the one that's switched. I'm not sure how much current it'll take to pull in the clutch, but I'll guess at least one amp. All that being said, that's the way GM does it and it's probably the same for most. As far as the 555 circuit goes , just Google "555 calculators" and I'm you'll come up with a suitable scheme.

[Externet]

Typically, if not by the compressor connector, there may be a diode somewhere in the harness that dictates the polarity to be applied. If reversed, the smoke will leak out of the diode and perhaps something else.
The diode absorbs the electrical spike at clutch turn-off.

The clutch is enabled to engage when the AC control is on AND one pressure sensor tell there is enough refrigerant in the circuit, AND when another pressure sensor tells the refrigerant pressure is low enough to start compressing but not too high to stop compressing.

So, all those conditions should be met for the clutch to be energized 'normally'

Get the schematic from your public library if in USA.

Miguel

[CeaSaR]

Thanks Gerty and Miguel,

I tested the clutch, 1 wire, and it engages/disengages just fine manually.
Still no cold, so there must be something more. Time to go find a
Chilton's.

CeaSaR

[Franklin97355]

Some garages will test your A/C for free hoping to sell you a recharge or "cleaning"

[Bob Scott]

I tested the clutch, 1 wire, and it engages/disengages just fine manually.
Still no cold, so there must be something more. Time to go find a
Chilton's.

Your AC system could be low on freon. The clutch will not engage if one of the pressure sensors detects low pressure. You can pick up a recharge kit with gauge at an Advance Auto parts near Phoenixville. The gauge should tell you if the freon is low.

But low freon would not account for the "essence of Ohmite" smell that you experienced.

[CeaSaR]

Actually, I'm rather sure that whatever caused the issuance of "odur"
is the real culprit. The system worked quite well before hand and was
only in dis-use for less than a month when it cooked. I immediately tried
the AC then, to no avail. As it was going into the fall/winter season, I
figured I'd wait. I'm adding it to my "list" of things to fix/get fixed.

Thanks for the help everyone.

CeaSaR