A/C Clutch hub not spinning with its shaft, making it impossible to unscrew the nut - any ideas for removing it?

carshalljd

carshalljd

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I've got a 1996 Mitsubishi Delica L400 and was hearing some pretty terrible noises from the engine a couple days after my car was in the shop for a different issue. I determined it was the A/C compressor clutch hub plate doing some funky stuff and rubbing against the pulley or something.

I tried remove it to take a look inside, but noticed that it was spinning independently of the shaft, making it impossible for me to take the nut off of the end of the shaft. Instead of taking the nut off, it just rotates the shaft. Normally I see people holding the hub steady to hold the shaft in place while they unscrew the nut but I can't do that since they are spinning independantly.

VIDEO OF HUB

Any ideas what I could do / why this is even happening? I'm trying to learn how to take care of this car without constantly taking it to the shop so any help is super appreciated. Thanks!
 
It looks like you may need an impact wrench to shock the nut off....easier still if you can jam the shaft somehow to stop it spinning.
John
 
You could try putting 12V on to the wire that feeds the clutch. (Connect the battery negative to the body of the alternator). That will energise the electromagnetic clutch, which might allow you to hold the pulley. (I don't know if the clutch would be strong enough though. It might just slip). Failing that, the impact gun is the answer.
 
Avocet said:
You could try putting 12V on to the wire that feeds the clutch. (Connect the battery negative to the body of the alternator). That will energise the electromagnetic clutch, which might allow you to hold the pulley. (I don't know if the clutch would be strong enough though. It might just slip). Failing that, the impact gun is the answer.
Click to expand...
This. Plus a strap wrench or similar idea around the pulley for extra grip.
 
Hey all thanks again for the advice and hello from across the pond lol! It took quite a bit of janky solutions but I finally got the compressor into a position where I could fit my impact wrench in and was able to shock that nut off.

After taking a look at the hub I'm fairly certain the issue is that the teeth on it have been stripped off. Here are some photos:

Hub exterior face
Screenshot 2024-06-12 at 8.08.56 PM.png

Hub interior face
IMG_0876.PNG


As you can hopefully see the teeth do not extend all the way to the end of the interior face. I'm assuming this means they were stripped off, but I don't know if they are supposed to go all the way to the end.

The good news is that the compressor shaft itself seems to be in pretty good tact:
Screenshot 2024-06-12 at 8.17.50 PM.png

Although it does have quite a bit of dirt/debris (is that ok?).

The bad news is I'm not sure I'm going to be able to find a replacement hub. I found the exact part here: https://www.amayama.com/en/part/mitsubishi/mr308511 but after searching around I don't see anywhere that sells it. Do y'all think there's any chance I'm able to use a hub from a different assembly or is this a replace the whole compressor type of situation?

Thanks again :)
- Marshall D
 
Crikey That's had a hard life! It's not great engineering practice to have the male spline going all the way into the female spline, because you need a bit of clearance to be able to tighten the nut, without running out of thread, but that seems excessive. I'm also curious, (if the nut was tight), how it was able to fail like that? There shouldn't have been any movement between the male and female splines, is the nut was tight.

Is the compressor itself seized? Can you put (I think you call them "vise grips", in America?) on the end of the shaft and turn it reasonably easily by hand? Is the aircon system still holding gas? The shaft doesn't look "wet", which suggests that either it ran out of gas (and lubricating oil) long ago, or the shaft seal is still good. If there is any doubt at all, over the condition of the compressor, it might be better to cut your losses and just replace the whole thing. If you think it's still good, can you get the maker's name and model number off it, and maybe search for electromagnetic clutch assemblies for that make and model of compressor. You might find the outer pulley is wrong (i.e. it is the wrong diameter or has grooves for the wrong type of belt) but you MIGHT be able to make one good one out of the two?
 
Haha yea I don't know who owned this car before me but I think it's likely been through 25 years of chaos lol.

I'm also very confused how this spline assembly could have even been stripped assuming that is the issue. Some additional context may help:

This problem started occurring immediately after I had the car at a shop in a small town in the middle of nowhere (broke down on a road trip). I find that mechanics tend to have trouble with it since its a Japanese import and was never sold in America. The issue ended up requiring a starter motor replacement, which I believe sits underneath the AC compressor. Other Delica owners have told me its not uncommon for a mechanic to mistakenly think they need to remove the AC compressor in order to get to the starter. So it is possible the mechanic removed it, and then replaced it incorrectly.

After the mechanic visit I drove the car 7 hours home, and didn't notice any issues (AC worked fine). The next day when I started the car though I heard horrific sounds coming from the engine and immediately noticed that the two top bolts on the AC compressor had come completely loose and the whole compressor had shifted so much I couldn't even screw them back in without loosening the two on the bottom first. In addition, the clutch plate was completely wobbling like so:

https://imgur.com/a/qfwqviP

Even with this issue tho I was testing it and the AC still worked and blew cold air. If you look closely the shaft did still turn a bit, although perhaps just not at 100% speed:

https://imgur.com/a/U4dyp6r


To answer your questions:
- I can turn the shaft reasonably easy by hand yes
- I don't know how to check if the aircon system still holds gas but it was still able to blow cold air out
- Model number is MSC130CV, Part number is AKC200A601D, Mitsubishi. After searching for the model number I found some potentially viable clutch assemblies! Thanks for that idea. I was originally searching by part number for just the individual hub which was producing no results.

I'm thinking of ordering one of these and trying it. In the meantime I was considering maybe jamming some duct tape or something into the hub and seeing if I can get a last couple weeks of life out of it while I wait for the new part to come. Is that an obviously stupid idea or do you think I can maybe get away with that lol?

Thanks!!
- Marshall D
 
That sounds encouraging then! I am also surprised at the damage to the female splines. There is a process known as "fretting" (or at least, that's the UK English slang for it!) where two mating components move, very slightly, relative to one another, and start to wear. It's a vicious circle, because once the movement starts, any amount of wear increases the gap, so the parts can then "hammer" at each other. You can see that an AC compressor clutch has quite a hard life. It will cut in and out, continuously, every few minutes, as the aircon system demands. Each time that electromagnetic clutch energises, it puts a bit shock load into the spline - especially when driving at higher engine speeds. In effect, it goes from zero RPM to about engine speed in a fraction of a second each time it cuts in! But how that movement started in the first place, is a mystery. The workshop would have had no reason to try and undo the nut on the pulley assembly.

Anyway, I don't think duct tape will work. These are big shock loads. The compressor is likely to require a couple of horsepower to turn it, and, as mentioned, when you switch the AC on, the belt needs to accelerate the compressor up to engine speed in a fraction of a second. To be honest, I can't think of anything that would withstand that kind of loading, other than hardened steel. Maybe some off that "chemical metal" stuff (an epoxy with metal powder in it), might stand a chance, but it's messy and you'll have to then try to clean the remains of it off the spline when you come to fit the new assembly. Personally, I wouldn't bother.
 
Just an update if anybody is curious...

While I was waiting for the new hub to come I decided I might as well just try throwing some duct tape into there and seeing what happens. That didn't do anything and I ended up taking it on a long road trip right afterwards.

Then a few weeks later the hub came, and I went to go try installing it, and noticed the plate was no longer slipping. So I tried turning on the AC and it just worked all of the sudden! I've been using it about a month now and it has not failed once. I jammed a lot of duct tape in there so maybe it melted and turned into some form of monstrosity of a glue. I'm too afraid to try replacing it with the new hub because there's a chance the hub does not fit it correctly, and that I will undo whatever magic setup is allowing this thing to work right now, so I'm basically just seeing how long I can get away with this lol. Thanks again for all of y'alls help!
 
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