Alternator Not Charging

**daveystoat** · 6th January 2021, 11:55

Hi All, I am after some ideas. The alternator on my Signum 3.0 V6 CDTI isn't charging. It has been replaced, the garage tells me there is no difference with the new one, so it is very likely something else causing it.

Anyone have any ideas? Thanks in advance

**northpole** · 6th January 2021, 12:51

It's a garage they need to do some diagnostics... let me say it this way if i was to bring my car into a garage and they wrongly diagnose this resulting in me changing the alternator, just for them to tell me it's not that i would loose my ****... 9 out of 10 times it means the auxiliary belt tensioner needs replacing( plus the belt itself) and if the can't find that out by themselves that is one bad garage... i'm not even a mechanic and know that this is one of the problems with the belt tensioners on most cars... it is the first thing they should've looked at anyway plus they should've tested the output of the alternator before replacing it...

I would say find another garage...

**Jon1796** · 6th January 2021, 13:03

Plug a diagnostic’s in and look on engine to see if canbus is reading anything. Also check continuity of cables to from alternator to battery.

**Vwdub2000** · 6th January 2021, 13:25

Check the basics the wiring, ground wire, positive wire use multimeter, clean up and check contacts that run back forth between alternator and the battery. It's older car add British weather more issues. That is where I would start.

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**daveystoat** · 6th January 2021, 15:04

Ok, thanks for the replies. It was the AA who diagnosed the alternator as faulty, not the garage. They have put a new alternator on, and it hasn't fixed the problem, they don't think it is the tensioner (the tell me there is no play in it and the belt is fine, that is only about six months old anyway).

They are waiting on their auto electrician to have a look at it, I just thought I would see if anyone had any ideas/experience on it here.

**northpole** · 6th January 2021, 15:15

Will be wiring to and from the alternator that causes the problem than... like I said some simple checking and a multimeter would do the trick...

They don't need an electrical guru for that.

**soulman** · 6th January 2021, 20:05

Having similar problems with my 1.9cdti Astra twin Top . Battery keeps losing charge if left for 3 days .Now the heating has packed up , no blowers . Temp gauge showed minus 32.6 ,now just F .

**Jon1796** · 7th January 2021, 10:27

Originally Posted by soulman

Having similar problems with my 1.9cdti Astra twin Top . Battery keeps losing charge if left for 3 days .Now the heating has packed up , no blowers . Temp gauge showed minus 32.6 ,now just F .

on that I’d check uec and bcm. From what I’ve read damp or corrosion on pins on back of uec, or failure of bcm.
silver kept draining the battery since I got her then when I added rain sensor to blacky and turned on comfort close blacky had same thing so turned off on both now fine.

**daveystoat** · 13th January 2021, 16:15

This is, finally, sorted out. Turns out it was the ECU not telling the alternator to operate, apparently because damp got into it. The ECU has been repaired and all appears fine now.

**Vwdub2000** · 13th January 2021, 16:47

Originally Posted by daveystoat

This is, finally, sorted out. Turns out it was the ECU not telling the alternator to operate, apparently because damp got into it. The ECU has been repaired and all appears fine now.

That's great, happy you got it sorted. Good diagnostic is key.

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