Car Won't Start

[shalmaneser 26]

So, just some confirmation that I'm on the right lines would be good...

 

Battery: 12.5 volts. Same when running. After a bit of a drive it's down to 12.3v. The instrument panel is acting a bit oddly too, tacho moving in time with indictators....

 

So....battery not charging.

 

I guess it must be the alternator or the cables from the alternator to the battery.

 

Using this highly technical diagram...

 

 

(with thanks to nickaliath's excellent thread! http://forum.205gtidrivers.com/index.php?showtopic=114881)

 

I've tested the resistance of the above +ve cable from alternator to starter to battery and there's not resistance whatsoever. Hence, the alternator's bust, amirite?

 

Anything I've missed? Are there any ways to actually test the alternator on or off the car? I've got a known good one winging it's way to me for £37.50... Earths all looks good as far as I can see, are there any 'standard' ways to test the earths other than poking your multimeter about?

 

I hate electronics.

 

Cheers boys!

 

Adam.

[S@m 156]

The +ve cable in that diagram is supposed to have no resistance (or as little as possible), its job is to transfer power from the alternator to charge the battery. as well as feeding the starter.

 

To test the alternator measure volts between the large connector on the alternator and earth. Should see 13.5-14v when running. If its 12v or less when running then try some revs to see if it improves but less than 13v and its likely the alternator is at fault.

 

If you suspect that your earths are dodgy try connecting a jump lead between the battery -ve terminal and the engine block/gearbox, if this improves matters then you know that the earths you have there already are insufficient.

 

Just a few ideas.

 

Sam

 

EDIT - Just to add, to rule out the cable connecting the batt-starter-alternator, test the voltage at the battery terminal and earth when running, it should be pretty much the same as the voltage at the alternator terminal and earth - if there is a notable difference then the cable is at fault.

Edited August 4, 2012 by Sam306

[shalmaneser 26]

wacked a new alternator on it and things seem much better although she's a bit hesitant starting...only seeing 12.8V although the battery was very discharged, I'm wondering if it's having trouble getting topped up as it were, might give it a go on a battery charger.

 

might give that jump lead earth idea a go to see if things can be improved...the stop light is glowing very very dimly (can only really see it at all at night!) so something might be up.