Altinator ISSUE, wrong car, but in general any car

Unread post by **citroenxm** » 26 Jul 2011, 15:15

Not much happens on the Renault side, so Ill try here as I need to know ASAP before anything else happens... however, it covers majority of cars...

Problem: Flat battery...

Battery state indicator showing green, an apparently ok battery.

Another known good battery fitted, car back to life, engine running a nice 14.2v into the battery, however, with ALL electrics on thats Lights and full beam, heater blower on full, rear heated screen on, rear fogs on.. engine idleing the Volts are now ALL over the plave, from 0 to 15v, 10v 12v 11v 15v 8v 0v etc etc....

Looks like altinator to me?? Correct??

Paul

Clogzz · Unread post by **Clogzz** » 26 Jul 2011, 15:54

Probably nothing wrong, I had that once when measuring with an el cheapo digital multimeter.
At idle with everything switched on, most of the current from the alternator goes into the load and the battery can’t smooth the pulsating alternator voltage.
Say that it’s a metering fault, not a measuring fault and an analogue or upmarket digital meter wouldn’t show that.

wotwot · Unread post by **wotwot** » 26 Jul 2011, 15:56

Sorry to state the obvious but have you checked the feed cable from the alternator, as in the connectors both ends.
If these are ok then the diodes are on there way out in the alternator.

AndersDK · Unread post by **AndersDK** » 26 Jul 2011, 19:52

Another wellknown issue is a bad earth on the alternator.

Sounds duff, but the problem is light alloy parts mixed with steel mounting bolts & nuts, which inherently calls for white-corrosion on the alloy parts.
The result is a high ohmic earth path.

The solution is to run a separate earth cable from any generator housing bolt to the battey minus pole - or a tested/serviced good earth point on the gearbox earth cable bolt.
This separate earth cable must of course be the same gauge as the charge cable from the alternator.

Unread post by **citroenxm** » 27 Jul 2011, 10:16

Thanks guys...

I was gussing diodes too... I didn;t beleve for ONE moment a varying voltage was normal! Thats Not a job of an altinator!

Paul

Unread post by **Peter.N.** » 27 Jul 2011, 11:12

You can get replacement regulator/brush units for most alternators from ebay for not a lot of money, about £12.00 for some. So unless the bearings have gone, well worth considering I would think.

Peter