Diagnose my alternator problems?!

-Mike-

-Mike-

-Mike-

Soldato
Joined
22 Dec 2002
Posts
10,165
Location
Minehead
Hi all,

Was sat out in the car the other day (I do various small trips at the minute) demisting my front and rear windscreens whilst playing a bit of music. Once it was clear I moved off the driveway, realised I'd forgotten something and came back.

On coming out to start the car again it was dead. I had a friend jump start me and then hooked up a multimeter to my head unit circuit. I've driven it for a few days now and observed the following voltage readings

Engine off - 12.4/12.5
Engine running - 12.4/12.5 initial voltage. Revving the engine mildly brings this to approx 13 but will drop back to battery voltage.

If I drive the car for a mile or so the voltage will go up to a nice 14v and stay there. However, if I put the lights on it will drop to around 13.6/7.

I'm guessing the reason the battery went flat is that when you put all the electrics on it drops to 11.6 which indicates to me that the alternator isn't doing its job and the electrics are robbing battery power?

Am I correct in the above assumptions and is there anything I can do with this alternator? Or is it new expensiveness time? :(
 
Mine does something similar... the voltage is all over the shop.

It's down to the voltage regulator on mine, I guess it's just a bit tired... been getting worse since I've been using my headlights/heater, as you'd expect.

It shouldn't be that expensive for a recon alternator, or you can whip a voltage regulator off an alternator in the scrappy.
 
Its a (SCREW MODZ) 306 Dturbo on a N plate. A new alternator from Mills is £105 exchange and the current one that it has is a scrap yard donor one (£35).


Where is this regulator situated AGW? We used to have an auto electrician but he's closed now. It'd be beautiful if it was just the regulator though :)
 
Here you go Mike. These are pictures of an alty I bought from eBay for the grand total of £5 :D

47877_Dscf0001_122_564lo.jpg


Under the black cover hides the resistor pack (large block which covers most of the alty) and the voltage regulator which holds the brushes.

Like so...

dscf0002ly3.jpg


Few bolts and the regulator should release...

dscf0003bi6.jpg


I did this one off the car and it was pretty easy. There's a 7mm bolt in the tightest of spaces which a normal socket won't fit into. Luckily, some pliers did the trick.

I tried switching it on the car and can't get the pliers at the right angle with the radiator and exhaust manifold in the way. Could get all the other bolts off fine though :mad:

edit... Err, that's an old Tandy bag btw... honest
 
Hi AGW,

Thanks very much for your picture guide! Much appreciated mate. So did the new regulator fix your alternator charging problems? If this is my problem then I'm happy to get a new regulator and shall refer back to this page at fitting time :)

Thanks again.
 
A wee update to this, in the hope of some more help.

I spent a hour cleaning the Skip that is my car out listening to music! I came to start it and it very nearly didn't go :( Went to my friends house to borrow a battery charger to pop her on charge.

So all connected up the red light is on - says 40% or less charge. I plug the charger in and it says that the battery is fully charged :confused: The sight glass thats supposed to tell you how charged the battery is just stays on black however. It USED to sit on green and was fine then.

So I'm now wondering, is the alternator not charging properly due to a duff battery? Its a flamm 600CCA jobbie, was quite expensive but I can't find the receipt to take it back :(
 
If you have been getting erratic voltage readings whilst the engine has been running then the alternator is at fault regardless of the condition of the battery.

The battery now certainly sounds damaged, maybe sulfated where it has been run down so often.
 
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