A weird one - 100amp fuse keeps going?

[Lloydy]

Hi all,

My 100amp fuse keeps going for some reason???

All was well until my coolant alarm went off having suffered a burst hose. The alarm went off and the main fuse went?

Today i changed a few hoses and replaced the fuse only for the same thing to happen. Despite the cooland being at max the alarm went off and the fuse went.

I have had the alarm fitted for a while now with no problems at all and if i do say so myself it is fitted properly and well.

This may not be linked to the alarm of course but i am left scratching my head (and wallet) to diagnose this.

Does anyone have a wiring diagram or something for me to see what this fuse (the 100am one on the battery) goes to???

Lloydy.

[Peg leg Pete]

Have you tried disconnecting the coolant alarm to see if the fuse blows again

[missfixit70]

I don't really understand how a correctly installed coolant alarm could blow the 100amp fuse, isn't that the main engine fuse? Is that the only fuse that's blowing? No other symptoms? Is it still going off after the fuse blows, or is it only before?
As Pete says, try disconnecting it & see what happens

[Lloydy]

Hi guys,

Thanks for the quick replies!

Im not convinced it is the coolant alarm either.

This is what happens:

-I turn the ignition on (not started yet) and everything works as it should. Including the coolant alarm which gives me a beep and a flash as it should.
-On starting the engine the alarm sounds (in a broken fasion) and the interior lights flicker. By this time the fuse has blown and when i turn the engine off all is dead with the 100 fuse blown.

I have checked the obvios shorts and cant find anything untoward??

Wiring diagrams for that fuse would help as i dont know what it protects.

[missfixit70]

Can't help with the wiring diagram, but it sounds like you have a big short somewhere, glow plug rail maybe touching somewhere? Anything else you've done recently that might've moved or disturbed something?

[Lloydy]

Hi Kirsty,

Since you asked i did make a boo boo recently whilst replacing my alternator belts.... I shorted out the alternator causing the same fuse to blow. I managed to slip with my spanner to do this!

Nothing else comes to mind though.... I really am perplexed!!

A friend of mine (mechanic with an interest in autoelectrics) is coming tomorrow to have a look so i will see what that turns up. I just know he will want the wiring diagram!

Any other thoughts are most welcome!!!

Cheers,

Lloydy

[rwill19050]

You have blown the diodes in the alternator causing a low resistance path to earth.
The alarm is sounding because it is 'seeing' a low voltage prior to the fuse rupturing.
Electronics does that sort of thing.

[Lloydy]

Thanks for the advice people...

I will get this mate of mine to check both when he gets here.

If the alternator diods were gone could the van have driven for a couple of weeks before showing any symptoms? We went on a road trip after the 'shorting incident'!

Please keep visiting this thread.... Need Elmo back on the road today for work next week!!!

Thanks

[missfixit70]

Check the output voltage of the alternator to see if it's giving full beans. Should be high 13 to low 14volts when charging.
depending on the number of starts & amount of electrickery used, you could get a few weeks, are the charge & sediment lights on at all with the engine running? This is an indicator of the alternator being fubar.

[Lloydy]

Hi Kirsty,

The alternator was replaced just before i bought it.... No no lights showing at all.

Will check the output though!! The road trip we went on used quite a bit of electric though and it still went on for weeks?

Do you know if the diods can be replaced or is it another new alternator??

Cheers,

Lloydy.

[missfixit70]

I'm pretty sure someone on here has replaced the diode pack, try a search.

[Manny]

To establish if it is the alternator that's cuasing the fuse to blow you could disconnect the plug from the alternator and then start the engine. I think you should be able to start and run without the alternator being connected. Running the engine without charging the battery for a few minutes should not do any harm and if the fuse does not blow you have the answer.

Manny

[teenmal]

Hi Lloydy,have a look at the cable going to the starter from the battery.Make sure its does not have a bare patch,and not touching the body.

Best of luck Mal..

Ps Did you get water in the starter motor or alternator when the hose burst?

[haydn callow]

Lloydy...have you sorted anything yet ? I would be very interested in the outcome as the alarm has been mentioned. Are you saying the alarm now sounds even though the coolant is up to Full?? If I remember correctly we wired it into the blinds. If the fault was there then the blind fuse would blow.
100 amp fuse sounds like a major short .

[Lloydy]

Hi all and thanks for looking...

Having spent all day with my 'man in the know' we have established that the alternator (new 3 months ago) has never worked properly. I have had to charge my batteries A LOT and not being an electrickery person couldnt figure it out why!!

The fuse was blowing under a series of conditions that had to be correct (or wrong!) for it to do so.

AS SUSPECTED... NOTHING TO DO WITH THE COOLANT ALARM OR MY FITTING OF IT!! The alarm was just sensing a voltage drop (or somehting like that) and so went off. Lets not forget, this all started when one of my hoses went (i know, i know Haydn) blew and if it werent for this device things would have been a lot more serious!!

Off to the alternator supplier for me and back on the road in a couple of days with any luck.

Cheerz all,

Lloydy