Auto Electical Expert - Mirez?

[dbc]

Need some one with a bit of expertise in auto electrics. From looking at Mirez's website that could be you.... :o

 

In process or sorting the Air Con on my MKII 2.3 and concluded that the compressor was knackered. Tried appliing 12V directly to it but the clutch wouldn't engage and the compressor itself is plastered in dye as if its failed internally and leaked.

 

After taking advice from a mechanic mate i've gone to the expense of replacing the compressor which I did last night along with the receiver drier and expansion valve.

 

Now I still need to get it regassed but just as a trial last night I thought I'll make sure the clutch engages on this one for piece of mind and nothing. Wired direct from the battery to the compressor and can't hear the usual clunck....

 

So my question is, what should I be doing to check if the clutch engages ok? On my old Mondeo when it had a leak elsewhere I was able to simply run a wire from the battery to the compressor and it would fire up OK ruling that out.

 

As the compressor is new I can't believe its duff before its even been used.......

 

Any tips on checking this out?

 

Many Thanks

[chrispb123456]

Hi there

There is a pressure switch located in the area behind O/S/F foglamp, one of it's functions is to disable clutch if there's no pressure in the system therefore protecting the compressor.

[Mirez]

Well thanks for the compliment!

 

Are you taking it out of circuit to test? You need to be doing that else you could damage the ATC controller as its linked. The clutch is dioded for some strange reason so it'll only work if you get the polarity right and thats 12V in on the Green/Black and ground on the brown. Since you are going direct then the pressure switch won't have any effect and it should just work - the only other possibility is a pressure switch internally but I'm not aware of the galaxy compressor having one fitted.

[dbc]

Well thanks for the compliment!

 

Are you taking it out of circuit to test? You need to be doing that else you could damage the ATC controller as its linked. The clutch is dioded for some strange reason so it'll only work if you get the polarity right and thats 12V in on the Green/Black and ground on the brown. Since you are going direct then the pressure switch won't have any effect and it should just work - the only other possibility is a pressure switch internally but I'm not aware of the galaxy compressor having one fitted.

 

Hi, yes testing off line so to speak, remove connector and wired straight from battery. Clutch does not engage. Took old compressor apart to see if there is anything that may stop the clutch operating but there is no obvious pressure internally.

 

There is continuity between the two pins on the compressor which I would have expected??

 

Found this online for the Sanden compressors and it says there should be about 3 ohms resistance but I am only getting 1 ohm - http://www.sanden.com/images/On-vehicle_test_procedure.pdf

 

What I'm getting at is that I don't really know what having continuity and lower resistance means as I don't fully understand how these clutches operate....any idea?

 

Thanks guys

[Mirez]

Continuity simply means a circuit exists, be it complete or shorted - electricity could flow from point A to point B.

To test the resistance properly you need to measure the resistance of your meter by simply puttng both probes together, you then subtract that reading from the actual reading to get the proper resistance, which I'm guessing will be even lower then 1ohm. Electroclutches are nothing more then a big coil of wire, when electricity is passed through it, it creates a magnetic field which pulls the plate against it (and thus engages drive). Typically, the more load the clutch has passing through it the larger the winding. On a 12V system resistance will be lower but still anything less then 1ohm would suggest the circuit is probably short circuited if not partially shorted. With such a low reading I highly doubt you'll be energising the whole coil, more likely just a very small part of it and therefore not enough to generate the electro-field needed to move the clutch.

[dbc]

Thanks - seems the clutch is duff then....very annoying on a brand new compressor!! s it possible to get these things refurbished?? Can't find anywhere online thats obvious.

 

Taking into account what you said about checking the resitance in my meter first I end up with 0.1 Ohm's....so no chance of it working......

 

Hopefully the online shop I got it from will be happy to exchange! Just relieved I didn't get it regassed first. Its only because the clutch was what failed on the original that I though I'd just check it out.

 

Thanks again.

[mk2vr6]

when you say you stuck it straight across the battery! you did stick a fuse in the loop? if not dont tell them what you did to test it :(