Three Steps Forward Two Steps Back

[ianbin2012]

Back to the cluster, put in a cluster from a petrol model with one red plug on the back all seems to be in order now apart from the airbag light on, hopefully an easy fix.

Alternator/battery light dimly glows all the time so i checked battery voltages:-

battery:-12.70v

Battery engine running:- slowly climbs to 13.80v

Battery engine running all electical`s turned on:- drops to 11.08v revving the engine only changes it by 00.20v

Is my alternator going bad.

[ianbin2012]

Also is the alternator model specific or will any alternator from either petrol/diesel fit?

[alan_131]

When you say the battery/charge warning light glows dimly all the time, is this all the time including when the engine is stopped? Engine running you should see about 14.6 v on pin 16 on the connector to the instrument panel. Did you have the airbag warning light on when the old panel was in?

 

Does vcds see airbag faults?

 

I think your charging was working ok before? You had 14.6v or thereabouts on the fuel level sensor engine running iirc. My impression is that your alternator probably isn't putting out proper output because it's not "activated" somehow, possibly due to a bad connection. When I was young this "activation voltage" (which drove the field coils because the residual magnetism wasn't enough to kick the thing into life) arrived via the instrument panel warning light. I expect it's smarter now.

 

I'd pull the small connection off the alternator (engine off, of course) and see what voltages you have there ignition off/on, and maybe retest with your old panel in. Of course, your alternator may be stuffed, but a bit of a coincidence. Maybe still some residual earth/feed issues?

 

vagcat.com might be helpful for part info.

Edited August 4, 2012 by alan_131

[ianbin2012]

When the old panel was in the battery light/airbag light/glow plug glowed dimly all the time with this panel in the airbag light is lit brightly and the battery light glows dimly all the time.

I connected a voltmeter direct to the main feed from the back of the alternator it was only putting out 13.40v which dropped when all electrics turned on.

[ianbin2012]

Took off the small plug to the back of the alternator red/blue wire measured voltages with ignition off and on:-

 

ignition off red to ground no voltage

" " blue to ground no voltage

 

ignition on red to ground 11.80 volts

" " blue to ground 10.40 volts

 

Ive also noticed when the engine is running the belt tensioner is jumping around.

Forgot to mention it is a 120 amp alternator.

[alan_131]

Hummn. My 99(which is here) only has the light blue wire and I've just checked - 10.5 ish volts connector to ground, with the connector off the alternator. Haynes shows both the wires you have, with the "extra" one connected to the ecu. I don't know if this is ecu voltage sense or management.

 

Disconnecting the instrument panel -

Battery volts, engine off,ignition on, about 12.6, engine running about 12.4.

Reconnecting the panel brings the alternator online and battery volts up to 14.7

 

I suppose it's just possible that when the alternator is connected to the small connector the voltage drops (due to a high resistance somewhere in the feed) so much that it's not enough to fire the alternator but this seems a bit of a long shot.

 

I don't think I can do it today, but I will check on the other car.

[alan_131]

Sorry but re-reading your updates -

Was the info about lights on your old instrument panel based on plugging it in today or from how it used to be?

If it was today, did you try battery voltages with engine stopped/running?

[ianbin2012]

The old instrument panel has been like that since i bought the car a couple of months ago, the old chap i got the car off said it was working fine until the was a big downpour of rain and the roads were saturated.

[alan_131]

Sorry but re-reading your updates -

Was the info about lights on your old instrument panel based on plugging it in today or from how it used to be?

If it was today, did you try battery voltages with engine stopped/running?

 

I have seen 14.6v on the instrument cluster connector pin for charge light with the engine running, but I may have started the engine before I disconnected the panel - don't remember I'm afraid.

 

Haynes says instrument lights earth thru e1, lh engine compartment. Does either turning on your lights or dimming the instrument lights make any difference....

 

Hopefully someone else may have something more definite....

[chrispb123456]

Have you checked the bunch of smaller wires attached to the battery + and earthing points and engine to body earth.