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freneticscribbler

Member

Registered: 2023-08-22

Posts: 3

2007 Dispatch Alternator Trouble

Hi all,

Recently become the owner of a 2007 1.6 Dispatch. Battery stopped charging a while back - showing 12V across alternator output to ground with the engine running. So I swapped the voltage regulator (/diode pack whatever you want to call it) out. Looks like the brushes were worn to nothing on what was probably the OEM part. Fair enough. Sorted - solid 14.4V in the system with the engine running.

Few weeks later, same issue - no output from the alternator, battery gradually dies. I replaced the voltage regulator again figuring it was a cheap part dud from the factory. Again. Sorted for a bit, until again a few weeks later when the same issue reappears.

I've no issues biting the bullet and replacing the whole alternator but I'm worried that will also only last a few weeks. I've a good auto electrician coming to take a look in a week, but I'd obviously rather get back on the road before then. Any ideas?

I've tried:
- different, known good battery
- removing and cleaning battery ground strap
- directly connecting battery ground to engine metalwork near alternator (trying to bypass any ground strap issues)
- to find out if there's a fuse for the charging circuit - I believe there isn't one?

Needless to say, I'm going to fit a voltage gauge whatever happens !

Last edited by freneticscribbler (2023-08-22 20:12:42)

OAT

Member

From: Borders/Dales

Registered: 2017-01-03

Posts: 1,013

Re: 2007 Dispatch Alternator Trouble

Far from an electrician here but my first though was the 12v "exciter" wire. 

But I don't think you have one.  I think the switching is done by the regulator you have already replaced.  Although, if the circuit was not being triped on when charging rpm is reached it would cause this problem.

Last edited by OAT (2023-08-23 14:39:44)

freneticscribbler

Member

Registered: 2023-08-22

Posts: 3

Re: 2007 Dispatch Alternator Trouble

Pretty good with electrics myself but more at home with 415V than 12!

Two connections to my alternator - big positive terminal I've been sticking my meter on and a sensor connection with a single wire - this could be the "exciter" you talk about?

My logic is thus - if there was a fault with the rotor/stator then the problem would, surely, not be temporarily fixed by replacing the regulator. It going bad after some time stinks to me of intermittent wiring faults (or a run of really bad luck with el cheapo replacement regulators...) ... this is why I jumped when the idea of a poor engine ground occurred to me earlier. Sadly that seems to have been a non starter. (ha ha. cry.)

With a 'good' regulator on it reads at 14.4V even at idle, it doesn't seem to need a throttle 'blip' to trigger like others talk about... may be a MK1 thing?

OAT

Member

From: Borders/Dales

Registered: 2017-01-03

Posts: 1,013

Re: 2007 Dispatch Alternator Trouble

As I understand it...

The exciter wire turns on the voltage regulator. When unpluged it, should have approx. 12.5 volts with the key on.

The exciter wire gets its power through the amp warning light. Key on, alt stopped, the bulb lights, once the alternator is turning it makes power and the amp light goes off. If the amp light bulb is NG the alt will not see power to energize the field windings, and it won't start charging.

https://turbobricks.com/index.php?threads/voltage-at-exciter-wire.336086/#:~:text=The%20exciter%20wire%20gets%20its,it%20won't%20start%20charging.

edit... I missed the point about you getting 14v plus on startup at tickover.

You havn't got a non original warning light bulb or an LED replacement by any chance?  Apparently the bulbs act as a resistor and LEDS don't work.

Last edited by OAT (2023-08-23 15:04:39)

freneticscribbler

Member

Registered: 2023-08-22

Posts: 3

Re: 2007 Dispatch Alternator Trouble

Appreciate that info - definitely got a working battery light but one I'll remember for future.

Took the voltage reg off and found a bigger issue... guess the armature is damaged and causing it to arc. Ordered a new alternator and reluctantly going to tackle fitting it myself tonight. Hopefully not a wiring loom fault that will kill the new part ... just crossing my fingers at this point in the name of having it back on the road quick!!!

Last edited by freneticscribbler (2023-08-23 14:46:22)