Hello, I'm at a loss and I'm looking for some help with the AC clutch on my 308. I moved the clutch to a new Rotolock York Style compressor as part of overhauling the AC system. The clutch worked on the old compressor, prior to removal. Once I installed it on the new compressor, I bench tested the clutch with a spare car battery and could spin the compressor with the pulley and hear the clutch click. It's all now back in the car. I pulled a vacuum, started to charge the system and no clutch engagement. I measure the voltage at the clutch and it's 11.8 Volts. I have a good ground but began to question everything so I decided to use that spare battery and go directly to the clutch wires - NOTHING. I don't get it? Why will the clutch not engage? I measured the resistance of the clutch coil at 3.1 Ohms, which tells me it should be ok. I'm baffled. What am I missing? Thanks in advance.
The clutch is engaged with a simple electromagnet. If it engaged on the bench, it must be something simple related to the 12v supply or ground.
Thanks for the response, The one variable I keep questioning is the spacing between the coil and the pulley/clutch pack. If the assembly on the new compressor results in a larger gap, the electromagnet will have less effect. Maybe it's on the "edge"? Is there a spec I should measure upon assembly? The difference between the compressor body and the shaft length define the gap. Only now I'm thinking I should have compared the dimensions of the original and new compressors. Any experience here? cheers,
I am not an expert but have disassembled a couple of 308 York compressor/clutch assemblies. As you know, the clutch is installed onto the keyed tapered shaft of the compressor with a single nut. The clutch itself is a stand-alone assembly. If the assembled clutch engaged on the bench when 12v was applied, I struggle to visualize situations when it ceases to engage just through the straightforward reassembly onto the compressor shaft.
There is a ground wire that attaches to the upper dipstick tube mount. Is it present, tight and all that?
In the past I made the mistake of having a poor ground connection to the compressor thus my fear here and applying a secondary battery directly to the clutch. As I know I’m overthinking things, I’m afraid I’m in for the pain of draining the coolant and removing the compressor yet again. I’m thinking the spacing is off and on the bench gravity helped as it was at a slight incline.
Why are you removing the compressor? I don't understand the issue I guess... The clutch will operate regardless of its orientation since, as pointed out, it's just an electromagnetic device. You mentioned 11.8 VDC at the wire to the clutch. Although I think that should be sufficient to activate the clutch, that's pretty low since a fully charged batt would be around 12.6+ and the voltage with the engine running would be higher. Low voltage might be the problem.
Depending on the difference, this may be a factor. I've replaced a ton of AC clutches, and setting the proper gap was standard procedure. Not going to try and speculate why it worked on the bench with power, and now it does not - even with power directly applied. If you've 100% verified the clutch has proper power and ground in the car, then it's not a power situation. I'd pull the unit and diag further.
Place an amp meter in line with the clutch. See how many amps the clutch is drawing. It should be something like 12/3.1 amps. That will let you know if the connection is good.
Thanks all, I think I’ve got a “semi-good” clutch. When the car cooled down and wasn’t running I went out and battery tested the clutch again and click click it worked. So I started the car and tried again. It clearly is slipping. Cold it would hold, then slip a bit, hold, slip hold and so forth. As it heated up it slipped more. In my previous attempt I had everything good and hot as I was bleeding the engine coolant before charging the ac. I think my future is clear - new clutch.
When the engine was running did you operate the clutch using a separate battery as you did when not running? If not, try that before condemning the clutch. Insufficient power could cause the problem - enough to barely engage, not enough to keep it engaged consistently under load.
Thanks Mike, I did exactly this, using a spare car battery. I could see the clutch catch and slip, bit by bit. I may not have a bad clutch, just a greater gap on the new compressor. cheers,
They slip if the pressure is too high and also if voltage at the clutch is too low. What do the pressures read and what is the present voltage read at the clutch measured through the supply wire and the ground wire feeding the clutch.
Please remember that the clutch is really controlled by the Hi/Low Pressure switch. To charge it you may need to install a jumper wire temporarily.
With motori off measure resistance from mounted plate clutch magnets housing and the neg battery termnal off battery. if more than 0.5 ohms you found problem The two suggestions above are about the ground; is easy 12V system, either power or ground is not there
Thanks all for the input. Looking at everything on the bench, it looks like the coil is not pulling in the clutch with enough force. The pully and clutch look very good. Is there an off the shelf coil for these? Anyone know where one can get a replacement coil or the part number to search on to fit the York style compressor? I looked at old threads and didn't see anything specific to just the coil. cheers
You get into a Rabbit Hole when you realize that the clutch even for the common York unit was a Ferrari Only Part. Single groove pulley plus the unique profile of the Polyflex bets.... Perhaps the coil itself is more common.
FWIW, when an allegedly competent AC shop worked on my 328, they overfilled it it with refrigerant which locked up the compressor, the clutch did not slip, the (properly tensioned) belt squealed/filled the room with rubber smoke/broke! IOW, the clutch should be able to engage/stay engaged regardless of the load on the compressor ASSUMING there is sufficient voltage being provided. If it won't then it sounds like the clutch assembly is faulty.
