HELP! - Electrickery problems!!

[Lloydy]

Ok... Im in the poo!

To cut a long story short my bongo seems to have lost its ability to regulate the amount of juice the alternator feeds to the battery. When you rev the engine you can see the fuse go from normal to glowing according to the revs... Then the fuse goes! DOH!

I have replaced the alternator after consultation with a mechanic but nothing has changed

The alternator aslo seemed to get very hot for such a short time working (30 seconds ish)

My only other thought is that there may be a separate voltage regulator somewhere? I cant see a bad earth and am not sure that would cause these simptoms anyway.

Any thoughts anyone? Elmo has been parked up for a week and a half now and getting to work is an issue. The wife has mentioned 'autotrader' allready!

Lloydy

[jaylee]

Tell me about it dude..
I was just under a quarter of a mile from home & the Mason alarm went mental.
I chanced it & just got back home, now i have steam coming out just under the drivers door & too dark to investigate...
& to cap it all were doing Woodlands on Friday.

[haydn callow]

As I understand it the alternator is self regulating. The regulator is built into the alternator these days.
The voltage from the alternator direct should be about 15 volts. Across the battery with the engine running around 14.5 volts.
You are blowing a hell of a big fuse. Got to be a serious short I would think. I would start at the alternator and trace every cable. Look for any damage, feel for any almost broken wires. A good auto electrician should be able to do resistance checks.
I could be way out as I am no electrician but I have wired up a few narrowboats from scratch and a half broken/frayed cable can be hard to find and cause havoc.
Best of luck. Wish I was nearer to try and help.

[haydn callow]

Steam under drivers door...top hose ??
Rear heater is further back.
Could be the hose over the starter.
My bet is top hose ...engine to metal pipe.
Hope to see you at Woodlands

[jaylee]

Steam under drivers door...top hose ??
Rear heater is further back.
Could be the hose over the starter.
My bet is top hose ...engine to metal pipe.
Hope to see you at Woodlands

Cheers Haydn, I know i'm not going to be able to drive it till it's fixed.
Just hoping the part can be sourced quickly & no other hoses have planned joining its condition..?
Will find out tomorrow & make a few calls.

I don't like the idea of sleeping in a Micra..

[haydn callow]

You o.k. to bleed it ??

[Lloydy]

Thanks for the replies guys...

Sorry to hear about your problem jaylee.

I tell you what... If i manage to get this sorted i will pop to woodlands and say hi... Was too late to book but could really do with a break!

Any more suggestions are more than welcome!

Lloydy

[Trouble at t'Mill]

Hi Lloydy.

My first thoughts were like yours - the regulator in the alternator (pretty sure there won't be a separate one...) is faulty allowing it to deliver an uncontrolled voltage. This, however, would also make your battery 'boil', and threaten to blow your lamps, etc. Do your headlamps glow alarmingly bright when you rev? If so, that would suggest the alternator itself is at fault.

Do you have a voltmeter to measure what's happening across the battery? As said above, this should be around 14-15ish volts after starting the car, falling to between 12-13V as the battery charges up. DON'T disconnect your alternator with the engine running to test it's output directly!! This WILL damage the regulator!

My second thoughts are different, tho'. Even if the alternator is over-outputting, I don't see how this would blow the fuse (I'm not sure which fuse you are referring to - is there one between the alternator and battery?) as for this amount of current to flow through it, there would have to be something on the other side of the fuse that's taking the current (like a 'short'). I can't think of what this could be other than the battery - but even then...

Is the battery ok? Does it fire up the car easily? I'm wondering if it has an internal partial short, that's essentially causing a 'short' across the alternator?

(You didn't run the can with the alternator, or the battery, disconnected for any time, did you?!)

Personally, I'd pay a visit to a local auto-electrician. I'm sure they could pin-point the problem in minutes - or at least dismiss the actual alternator or battery as being at fault.

[haydn callow]

The above all sounds like good sense to me.

[jaylee]

You o.k. to bleed it ??

Nope.. But my main concern at the moment is getting a replacement part!

[jaylee]

Thanks for the replies guys...

Sorry to hear about your problem jaylee.

I tell you what... If i manage to get this sorted i will pop to woodlands and say hi... Was too late to book but could really do with a break!

Any more suggestions are more than welcome!

Lloydy

Thanks Loydy, & i was just patting myself on the back for getting shot of a nasty trojan virus on me puter last night too!!

Sorry to buss in on yer thread..

Hopefully see you at Woodlands..

[rwill19050]

What about a short in the battery itself?

[Simon Jones]

When you rev the engine you can see the fuse go from normal to glowing according to the revs... Then the fuse goes! DOH!

Which fuse is it? High voltage wont blow a fuse, but high current will. I cant see it being the current from the alternator being too high either - its more likely to be a short somewhere. The fuse that blows will give an indication where the fault may lie.

[Trouble at t'Mill]

Electrickery is well named...

Yes, it's true that it's current (the actual 'stuff' flowing through the wire) that will cause the fuse to melt, but the current will rise in direct proportion to the voltage. So, if the alternator voltage is increasing out of order, the current flowing through each connected component will also increase.

Yes, I'd love to know what fuse the OP is talking about too!

[haydn callow]

I think the problem fuse is the main 100amp one under the bonnet.