Alternator Nightmare

[MAZABON]

hi all

over the last week or so i have noticed the starter motor has sounded a little weak, ( put it down to me being paranoid ) but then yesterday it happened, very slow turning over and just about got it going, anyway i gave the battery about 15 hours bench charge and went about some testing and it was grim! no increase in voltage when engine running !, in fact the voltage was droping:( , what is a bit of a concern is that in about 5 minutes of running the alternator was pumping out more heat than the turbo !! ????? , i have ordered a new alternator but anyone got any ideas about all the heat????, belt tension feels about normal.

gutted, i prefer being on techie to help others with issues not posting them

[g8dhe]

The alternator generates AC internally this is then rectified using diodes to create the DC voltage for charging, the most common electrical problem is that one (or more) of the diodes will fail short circuit and then the alternator spends its time heating its windings up!
In the Bongo diagram below, the Alternator is on the right with 6 diodes (Arrows with flat heads), these are what often fail;

[MAZABON]

thanks for that Geoff (g8dhe), i do like to know reasons for things for future reference

i can hardly believe the heat that it was generating

although i have been driving it around ok for the past week with suspicions of an issue, now i know about the amount of heat being generated the bongo is staying put untill the new alternator arrives and i can get it fitted.

dont want my beast bursting in to flames !!!

Thanks again

Mark

[MAZABON]

update

info for anyone who needs a new alternator ( a bongo alternator change is probably the most simple i have ever done on any vehicle )

i thought perhaps a couple of hours job so ill give the battery another quick bench charge whilst i am doing it, what a waste of time and effort that was!

20 minutes later new alternator fitted and i was carrying the battery back out to the bongo to refit it, sorted in all probably about 30 minutes including a retest on charging voltages to both batt's & belt tension check.