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Discussion Starter · #1 ·
Hello,

Driving our Beetle back from Syracuse and the A/C went out.

Figuring it might be low on R134a I picked up some "Cool 'n a can" and connected it to the port. It pegged the dial, which isn't a surprise considering the compressor was not running. So it's pretty clear the system didn't loose a the charge. (if the compressor was running, we would have a clear difference between the high side and the low side. With no running of the compressor the pressures equalize)

The compressor clutch isn't engaging when the switch is kicked 'on'. The cooling fan(s) are kicking 'on' full boar and I did check the fuses and the under hood fuse panel.

We seem to be getting at all times a 9vdc reading at the compressors electrical plug. Seems a bit odd. It's the same no matter if the switch is on or off. This of course is out of circuit. I've no real way to check this as I lack a wiring diag.

The engine also has a very clear "Surge" at idle when the A/C is turned on. It is like the engine knows to kick the compressor on, and the surge happens like the compressor is 'on'. (It's not of course....we can see it sitting there)

The compressor isn't seized, it free spins normally.

Any ideas would be helpful. I attempted the old trick of bypassing the pressure safety switch, but as soon as I unplugged it? The surging stopped---so we aborted that test, as we can tell it's functional.

--again, the cooling fan(s) are both running at full power. And the problematic fuse is checked and it's fine.



S-
 

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sounds like the fcm

Could be your FCM module since the compressor clutch power go's through it. I don't understand the 9vdc issue though unless the relay is partially stuck inside the FCM. You'll still gonna have to remove some of that Freon back out since low on Freon was not the issue. for test purposes Can you jumper the compressor directly with battery voltage and see if the clutch engages? comes on. I believe the green wire is the plus and the black wire is your ground. Just don't leave it like that too long or with too much Freon, its just for test purposes. If that works normal then you'll have to find which switch is keeping the compressor clutch from not engaging, there are about 2-3 of them. low presser , high presser, ambient temperature, coolant temperature out of range.
 

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Discussion Starter · #3 ·
Pretty sure the system didn't get overcharged. It actually has an overpressure safety built into the gauge head. I gave it a couple of shots just to see if it would respond, and it kicked it back out the handle. (The system wasn't running, and sure had some pressure built up into it!) I figure get it running and the high side would go back to the high reading, and the low side would kick/cycle back around the 15-25lb mark. If the system is just sitting there not running, both sides will equalize. I'll be honest, I'm guessing at this point, because I'm not in front of it looking at the specs.


I'll be hitting the yards for a couple of fan control modules. The 9vdc at all times really makes me scratch my head. I did a 110 mile round trip with the car, and except for the lack of A/C? It did quite well. That voltage reading was under "no load". I couldn't backprobe the connector due to the really sad place they routed the radiator hose.

I'll play with it tomorrow more. Right now it's enough that both fans are still running fine.

S-
 

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Discussion Starter · #4 ·
Well..that was a whole lotta nothing...

Hit the yard, scored an extra 3rd brake light and the fuse box thingie that goes on top of the battery out of a rolled 1999 Beetle.

Found 1 Fan control box...it had green goobersnot on one of the terminals. Cracked it open to find heavy rust on the relay. Tossed it back...

Went to our local salvage yard--Talked them from $30 down to $15 for the part. (I can buy one from Euro Parts brand from Rock Auto for about $30.)

Installed, and still no compressor operation. Decided to do testing with the engine cold, as not to smoke my arm up on the radiator hoses. Still have that oddball 9vcd?!?! But I did use the "Scope on a Rope" (as one of the youtube channels calls it) and found we have a 12volt signal strong enough to kick the test light 'on' when the A/C is on. It matches with the engine doing it's "lug/Surge". So the computer is commanding the compressor to kick on, but the compressor clutch is dead.

Pulled the connector and did an ohm test. Open circuit. Gonna need to replace the clutch to get A/C back on again.

Wanted to keep everyone interested in the loop.

S-
 

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jumper

Well..that was a whole lotta nothing...

Hit the yard, scored an extra 3rd brake light and the fuse box thingie that goes on top of the battery out of a rolled 1999 Beetle.

Found 1 Fan control box...it had green goobersnot on one of the terminals. Cracked it open to find heavy rust on the relay. Tossed it back...

Went to our local salvage yard--Talked them from $30 down to $15 for the part. (I can buy one from Euro Parts brand from Rock Auto for about $30.)

Installed, and still no compressor operation. Decided to do testing with the engine cold, as not to smoke my arm up on the radiator hoses. Still have that oddball 9vcd?!?! But I did use the "Scope on a Rope" (as one of the youtube channels calls it) and found we have a 12volt signal strong enough to kick the test light 'on' when the A/C is on. It matches with the engine doing it's "lug/Surge". So the computer is commanding the compressor to kick on, but the compressor clutch is dead.

Pulled the connector and did an ohm test. Open circuit. Gonna need to replace the clutch to get A/C back on again.

Wanted to keep everyone interested in the loop.

S-
Glad you are making progress by going directly to the source of the problem it's always good to either jumper the clutch directly with power or ohm it out with a digital meter. Still don't explain why the 9vdc since you claim the coil clutch is open that means you should see the full source, 12 vdc when the clutch is engaged. Sounds to me like the clutch coil is gone bad and pulling it down to 9vdc when it's engaged. IMO
 

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Discussion Starter · #6 ·
That's the oddest part of this.

The harness was unplugged when I did the voltage test. One side had nothing (ground). The other side has 9vdc and it cycles to 12vdc when the computer commands the clutch to kick on. The same time we get a mild effect on the idle, just as I would expect. Compressor kicks 'on' and the engine surges a bit so it won't stall or bog down under the new load.

As for that 9vdc? Even 9 volts would be enough to trip the test light to a degree. So while I'm reading 9vdc at that connector to ground--it's not strong enough to light the test light. But when the computer tells it to supply the 12volt for the clutch? She kicks on full power at the test light.

Just one of those oddball things. Sense it happens with both the old fan module and the replacement. I'm not sure what to make out of it.

I'll be swapping the clutch coil tomorrow. No sense in swapping out the bearing or other spacers and such, as they are still in good shape. Just trying to plan out how to do this..space is limited.

S-
 

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space

You aren't kidding space is limited keep us posted how things turn out for ya. I think the reason you are seeing that 9 volts when the computer is not actuating the clutch is because that voltage is always there and then to turn and complete the circuit the computer sends a ground or negative to the black wire to actuate the clutch.imo
 

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Discussion Starter · #8 ·
If I don't have to do that again? I'll be a happy camper

Couldn't tip the compressor 'up' at all. Had to tilt it downwards and cheat with a screw driver through the upper compressor hose, through the oil dipstick resting against the front clip.

Managed to finish the job, but who in the he$% decided to make the space between the ears of the alternator and compressor razor thin???? Compressor finally wedged back into it's home. The alternator? Next time that's out I'll hit the ear on the bench grinder to shave off about 1/32 of an inch. Wound up getting the bottom kinda snaked in and the top didn't want to go in. Just as hard as it came out.. Did the "Tap and Twist" with the hammer on the ears to get them started and then twisted the alternator until it did a wedgie into position.

Pretty sure that alternator could have both bolts fly out--and it still wouldn't budge. On the lighter side? Love the belt adjuster setup. THAT they got very right!

A/C blows cold again. Starts up with noise--kinda expecting that considering the amount of scale and rust built up on the clutch assembly. That should clean itself up over time I would expect. No signs of any spacers? Just the washer on the shaft that got reused. (unless that is the spacer? In any event...it's installed)

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success

Good to hear you were successful, congrats you are now an A/C mechanic. :banana: oh btw you don't need to shave off anything of the alternator to make it fit next time you just need to use one of it's original long bolts and on a wooden workbench push the
round wedge nut (red arrow in picture) back with a small hammer, usually about 1/32 will do fine. good job man
 

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Discussion Starter · #10 ·
Shows how long I've been out of the industry. It didn't even occur to me to shove that little bas.... (insert your own letters) back a whisker.

As for now being an A/C tech? I used to be over 22 years ago LOL. I left the industry back about 22 years ago when the shop I worked out of brought in a manager nicknamed "Little Adolf". Changed fields after that bad time. Trying to remember my old training on these newer cars is a challenge indeed.

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little adolf

Little Adolf? LOL :D we had a guy in our shop we called that a few years back. well good luck and remember we are here to help each other out I usually just log on between Monday and Thursdays because i'm too busy on the weekend to even get on the computer.
 
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