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[iansoutham]

Has anyone had issues with X20XEV aux belt tensioners losing their tension?

Reason for asking is that I have randomly seen the battery light on full at night intermittently but yesterday drove to Wales and back from Kent and the return journey was in the dark. The light kept changing in luminescence depending on load, wipers, indicators, etc and when the light wa a brighter I thought that maybe I could smell something but at 70mph you won’t hear a belt squealing.

I tried a few things and when I reduced the load by turning the aircon off, the light went out completely after about 5 seconds and stayed out until you turned the aircon back on. This would bring the battery light on about half brightness and then drop down, I suspect as the belt slipped and caught back up with the load.

I am going to check the belt today and probably change it during the week, but was also thinking about the actual tensioner and if it could be the main reason?

[iansoutham]

Quick update, have been out to the car and all pulleys spin freely, alternator, aircon (and actual pump part, but just free-wheeling pulley). Aux tension set pulley sounds like the bearing is a little dry but no free-play. The belt has been slipping, there is no dust but the rib teeth are “shiny”.

Is there a minimum force setting for the tensioner?

[Doctor Gollum]

Your barking up the wrong tree.

Start with the alternator/battery. Run through Kevin Woods' starting and charging tests and fix whatever is actually broken. 

[iansoutham]

Your barking up the wrong tree.

Start with the alternator/battery. Run through Kevin Woods' starting and charging tests and fix whatever is actually broken. 

Should have said (as I knew the at would be the 1st thing someone would say), did that the other month when initially looking for the problem. All good.

[Raeturbo]

Try a new belt first just could be stretched /worn out maybe. Put everything on and listen for squealing under the bonnet.  Check Earth.  Could be brushes in the alternator?

[Andy B]

The charge light on my Omega used to glow faintly, and got slightly brighter when rev'd. I crimped the positive battery cable clamp a nudges tighter and it sorted it.

[Doctor Gollum]

A worn or stretched belt would soon get thrown and it would squeal and slap like a stuck pig in the meantime.

The belt is a service item, so should be changed if history is unknown, but it isn't the issue.

[iansoutham]

A worn or stretched belt would soon get thrown and it would squeal and slap like a stuck pig in the meantime.

The belt is a service item, so should be changed if history is unknown, but it isn't the issue.

On that I do completely agree, it may be a victim of another problem but there was still tension on the belt. Been out for a drive and when hot, the tensioner pulley bearing is not in a good way and feels a little bit rough so definitely needs changing anyway. I will try to find one of my digital torque wrenches and see what torque figure it takes to make it move for reference.

I used to build alternators and starter motors at a previous job and have a “jig” for testing so I know alternator is okay from previous test when looking for the fault prior.

Out of due diligence, I will double-check wiring losses though…

[Doctor Gollum]

Kevin's test covers the battery terminals, but most simply do the engine on/off voltages.

New pulley is about a tenner, even for a GM one.

The bearings can usually be repacked, but the plastic pulley will deteriorate quickly if it gets hot.

If it has a separate idler, I can't honestly recall on the four pots, then belts and braces would swap that too

[iansoutham]

Latest details:

Aux tensioner pulley was bone dry so removed the seal and regreased properly.

Battery figures are below

Resting charge 12.62V
Resting charge with Lights on 12.2V, returning to 12.6V after turning off

Idle charge 14.2V, electrics off
Fast idle charge 14.3V electrics off

Idle charge heating on, no a/c 14.15V
Idle charge heating on, a/c on 14.0V

Idle charge heater, lights, rear window 13.45V
Fast idle charge heater, lights, rear window
13.5V

Idle charge all electrics (everything you could possibly switch on) 12.4V
Fast idle charge all electrics 13.3V

Wiring check battery to alternator
14.05V at alternator
13.6V at battery

16.71 lbft torque to lift tensioner arm

[Doctor Gollum]

Fast idle voltages are low and your dropping half a volt to the battery. The cable is only two feet long, so that's going somewhere.

[iansoutham]

Only update today is that the light came on dimly 1st thing this morning and then went out after a couple of minutes, not to return all the way to work.

Will check again the evening on way home.

Too soon to say really…

[cam.in.head]

as mentioned above somewhere,a voltage drop of that amount on a short cable ( of possibly 6 or 10 mm/2 )would suggest a bad or failing lug crimp joint so id be recrimping them first and making sure their connections in the fuse box on the battery terminal is all good.you could also prove it by hooking up another cable too to see if the volt drop virtually dissapears.
otherwise an occasional charge light can come from low brushes ( this would progressively get worse)or a bad diode or diode joint.i think they are just crimped rather than joined properly ?
my moneys on the cable crimping thou .( main starter cable worth checking too as those can work loose over time.)

[iansoutham]

as mentioned above somewhere,a voltage drop of that amount on a short cable ( of possibly 6 or 10 mm/2 )would suggest a bad or failing lug crimp joint so id be recrimping them first and making sure their connections in the fuse box on the battery terminal is all good.you could also prove it by hooking up another cable too to see if the volt drop virtually dissapears.
otherwise an occasional charge light can come from low brushes ( this would progressively get worse)or a bad diode or diode joint.i think they are just crimped rather than joined properly ?
my moneys on the cable crimping thou .( main starter cable worth checking too as those can work loose over time.)

Most likely suspect for me, probably at battery end as those joints are normally alloy connectors.

I do have a way of testing the cables, but it is a 2 person job really using the “jig” I have for alternator testing.

When doing the tests, the cable and connections all stayed cool, even under load so may be internal wiring corrosion somewhere, or something completely different..

[Doctor Gollum]

Bench testing any single component doesn't give a full picture... A weak bench pass won't   it in situ if there's a combination of things going on.