Cool/Heat: A/c clutch problems.

[Aussie Hawk]

I've been trying to get the air conditioning on Bill Pressler's old '64 Daytona up and running. I initially thought the clutch electromagnet had burnt out, and had it checked by an A/c workshop - all OK. I stripped the clutch mechanism right down and cleaned it, all looked OK inside, reassembled and put back on the car, still no go. The a/c guy did mention if there was too much clearence between the magnet and the clutch it wouldn't pull in, which makes sense. I'm going to shim out the magnet mounting tags on the compressor body to see it that helps. In the mean time does anyone have any experience with these York compressors? At present it's not engaging at all, even with seperate test wires.

[hausdok]

Hi Matt,

Is the system fully charged? Automotive AC systems are often equipped with a low pressure switch that will turn off the compressor when the system loses pressure. It's been a loooonnnnnng time, but I seem to recall that the low pressure cut off will shut the compressor off somewhere around 20 psi and it won't come back on until pressure is above 40 psi (?).

[Aussie Hawk]

Hi Matt,

Is the system fully charged? Automotive AC systems are often equipped with a low pressure switch that will turn off the compressor when the system loses pressure. It's been a loooonnnnnng time, but I seem to recall that the low pressure cut off will shut the compressor off somewhere around 20 psi and it won't come back on until pressure is above 40 psi (?).

Hey Mike,

I've actually connected power directly to the magnet with no engagement, so this would bypass any cutout switches.

[tbirdtbird]

the magnet ohms out OK?
did this just suddenly quit or has it been sitting around a long time

[SN-60]

Yes that is strange. Installed on the engine would give it proper ground, and with Your test wire it really should bang right in (esp. after all Your good clean-up work). Could there be an open inside electro mag. itself? Say Hi to Brian G for Me.

[hausdok]

I've never experienced this, so I don't know the answer; but what happens when polarity somehow gets reversed on one of these - do they still function?

[whacker]

It's just a magnet, polarity shouldn't matter. I vote for a bad connection or a broken wire inside the magnet. Power up the magnet, then see if it attracts a magnetic compass needle. Is there some reason you want to continue to use the York compressor? You should be able to replace the entire compressor and clutch with a Sanden 508 for about the same cost as a new clutch for the York, and it is a better compressor.

[Aussie Hawk]

the magnet ohms out OK?
did this just suddenly quit or has it been sitting around a long time

I haven't done an Ohmns test yet, what reading should I look for ? I only got the car just before Christmas, it wasn't working then. When I emailed Bill for some history, he said it hadn't worked while he had the car, I don't know how long Bill had owned it.

I'll try the compass needle test as well.

Thanks all for the input.

[WCP]

Wiggle the wire into the magnet coil with 12 volts applied. The wire may be broken due to flexing over the years - a common problem. If that's the problem, I don't believe the coil is repairable.

[tbirdtbird]

just put an ohmeter across the magnet leads to measure the resistance of the coil, you should get maybe 5 ohms or less, but certainly nothing over 50; this is an easy way to tell if the magnet coil is burned out, which would give a very high reading

[Aussie Hawk]

just put an ohmeter across the magnet leads to measure the resistance of the coil, you should get maybe 5 ohms or less, but certainly nothing over 50; this is an easy way to tell if the magnet coil is burned out, which would give a very high reading

4.5 Ohms across the coil - what am I missing here ????? I energised the coil with a seperate battery, nothing. I pushed the clutch plate closer (manually) towards the coil through the access holes in the front plate, to test the A/c mechanic's statement that 'if there's too much clearence between the coil the the clutch it won't pull in'. It still didn't activate. What the Fruit is going on ??????? Any help greatly appreciated - remember it's high summer here now > 100 degrees, and >80% humidity.

[Chucks Stude]

Activate the coil, and hold a wrench toward the side of the magnet. It should pull the wrench toward the magnet. Are you sure the engine is well-grounded to the frame? If someone tried to wedge the clutch onto the shaft, and broke it over the key, that would probably mess the whole thing up. They are available on Ebay etc. Does the compressor turn, when you turn the center section of the clutch? Should be able to do it with your hand. Just a few things to check.

[Aussie Hawk]

Activate the coil, and hold a wrench toward the side of the magnet. It should pull the wrench toward the magnet. Are you sure the engine is well-grounded to the frame? If someone tried to wedge the clutch onto the shaft, and broke it over the key, that would probably mess the whole thing up. They are available on Ebay etc. Does the compressor turn, when you turn the center section of the clutch? Should be able to do it with your hand. Just a few things to check.

Hey Chuck,
There's no sign of 'magnatism' at all. I even put some small pieces of metal swarf on the top of the coil to see if they would react when I energised it - nothing. I've been using a seperate power wire directly from the battery, I'll try a seperate ground wire as well and see what happens. The clutch is fitted to the tappered shaft and keyway correctly. The compressor does turn by hand. I'm beginning to think the A/c guy was full of it when he told me it had tested OK. If the seperate ground and power wires don't work I'll pull it off again and get it tested by another shop.

Thanks for your input guys.

[jnormanh]

If you put power to the compressor clutch, you should hear a definite click or clunk when it engages. Sounds like an open circuit in the coil. If you get really lucky, maybe you can find and repair it. If not, maybe an electric motor repair shop can rewind it.

[tbirdtbird]

if there is insufficient refrigerant in the system, usually less than 30 psi, there is a low-pressure cutoff switch which will stop the compressor magnet circuit from being activated.