A/C clutch not engaging. And mystery part.

mustang_gt_350

Veteran Member
Joined
May 18, 2010
Location
BFE
TDI
98 jetta
Ok, i have been trouble shooting my A/C issue this afternoon. I noticed last year it would work intermittently. If i remember correctly if i would push the a/c button a few times when it wasn't working it would start to work again, then i think it just went to randomly work.
So far i have shorted the low pressure sensor down by the drier and nothing, and the same with the temp sensor on the upper radiator hose, nothing.
I have not hear my fans running in a long time but then again it has been winter and if it was running i wouldn't be able to hear them while driving. But the same goes with the shorting of the temp sensor, no fan and no clutch engagement.
All of the fuses under the dash are good, and the relay does work. However i noticed that if i start the car and push the A/C button i can feel the relay click, and unclick. but after 2 or so pushes it no longer does it. So the ECU must be shutting it out? I'm not sure where to go from here other than the fan controller (under the coolant bottle?) and possible the high side switch and try to short it?
Anyway while looking around i noticed a dark spot on the cover of the clearish plastic lid on this thing mounted on the firewall near the coolant bottle. I opened it and its obvuiosly burnt.. but what is it?
https://ibb.co/m4bRYy
 

mustang_gt_350

Veteran Member
Joined
May 18, 2010
Location
BFE
TDI
98 jetta
I Also noticed my FCM only has 1 fuse installed in it. the main bar is there, and the left fuse spot has a 20amp but the right side is blank. Not sure if this is a problem as it has worked fine before but maybe its for low speed or high speed and i only had one speed since the fuse was gone?
 

lisab4

Veteran Member
Joined
Oct 20, 2013
Location
Belgium
TDI
1996 Passat B4 1.9 TDI
That thing in the picture looks aftermarket? Doesn't look like OEM VW to me.
 

mustang_gt_350

Veteran Member
Joined
May 18, 2010
Location
BFE
TDI
98 jetta
Nope, no gauges. Maybe i will have to pick up a set.

And thanks for the ID I had no idea what it was for. I will check into why it burnt.
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
Maybe, unless it's being shut down by more than one sensor, which it could.

Have you tried to turn the compressor by hand (with socket wrench)? If you can't turn it you might have a situation where the compressor is locked up.

Might be a situation where you want to have a shop check it out.

Steve
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
If all you’re looking to do is energize the clutch, put 12v to the coil. It’ll at least rule it out.

-Todd
 

mustang_gt_350

Veteran Member
Joined
May 18, 2010
Location
BFE
TDI
98 jetta
I need to spend a little more time with it. It won't be for a few days. I tried to unplug the connector at the compressor but the whole damn thing moves. I need to try to unplug it again and hit it with 12v. But I did check it before I made the post it isn't locked up. I can spin the clutch over by hand. It's just engaging for some reason. Will a bad fan relay cause it to not engage even with the low sensor jumped? Looks like it will be a DAM and chasing game on this one. I will probably just grab a set of gauges too if I can't find it with just the DMM. My snap on meter took a swim last summer and ever since has been giving me issues and it gave me the last onebyestersay so I tossed it into file 13. Now I can't did my freebie from harbor freight lol
 

iluvmydiesels

Veteran Member
Joined
Nov 21, 2015
Location
phila area
TDI
AHU
thats not the clutch your spinning, the pulley will spin freely anyway. its the same as if you had the belt on and ran motor, whatever. the trick(would be) getting the clutch to engage and then turning it.
 

mustang_gt_350

Veteran Member
Joined
May 18, 2010
Location
BFE
TDI
98 jetta
Is the clutch also spinning when you activate the AC?

Clutch (http://www.waltinpa.com/images/VW Jetta - AC Clutch.jpg)
No, the clutch is not engaging when i turn the switch on, no fans, nothing. The only thing that is working is the light on the A/C button and the relay. The relay will engage and dissengage every time i push the button on and off when the key is on but the engine is off. Howevre, when the engine is running and i push the a/c button the relay activates, i push the button again to turn it off and the relay releases as normal, but on the 2nd push the relay does nothing. So whatever it is i beleive the ECU is seeing something it doesnt like and is not sending power to the clutch. I still need to get time to probe the harness and see if its actually sending anything to the clutch. The car is running, and thats all i really need. I have a few other projects that are higher priority the last week so i haven't had any time to do any more trouble shooting than the 10 min i spent on it the day i made this post. The damn Vanes on my librty crd turbo are siezed and i'm working on that currently lol. If I need A/C i just take my focus. lol
 
Top