Electrical gremlins

[MilesA]

Having garaged the car 2 weeks ago and switched of the battery cut off switch, it was dead as a dodo this morning. Battery seemed OK but system dead, deceased, etc.

 

Traced to the 35 amp fuse which once replaced enabled everything to fire up. Any thoughts on what caused the fuse to blow presumably after I had switched of the ignition but before activating the cut off switch?

 

I noticed that the live clamp n to the battery is very close to the battery bar so packed the bar to move it away from the clamp and applied a rubber strip to the top of the bar. Unrelated?

 

Once I had the car going the red light on the centre instrument panel seemed to be glowing from time to time. Imagination, coincidence or something to examine and if so what? I also seemed to experience some poor fuel delivery problems (electric pump) but as I had just emptied the tank of unleaded at my local BP station (it literally ran put of unleaded whilst I was filling up - never heard of that before) perhaps I had picked up some crud as the problem cleared after about 5 minutes of spluttering. Could it have been part of the electrical gremlins though?

 

Any thoughts appreciated as I don't really 'get' electrical things.

 

Thanks - Miles

[vivdownunder]

Miles, the problem could be with the contacts inside the control box on the firewall. They can be cleaned with something non abrasive, but when the thing plays up it's often on its last legs.

 

Trouble is the repro's have been bad news, so perhaps best to try and save the original. It's not a thing to play with unless you feel confident, so maybe get an auto elec to have a look.

 

Viv.

[sidescreen]

Miles,

 

If there's something wrong with your control box why not contact http://www.coxautomotive.co.uk/supports.html for an eventual overhaul of your original control box.

 

Regards - Raymond

[RogerH]

Hi Miles,

if you have little eclectrical experience then you need to do things methodically an one step at a time.

 

Have you got the circuit diagram - get it enlaged to A3 (or 2 x A4) and encapsulated if possible.

Attack one thing at a time.

The fuse - clean the contacts to all the fuse holders and the cable connections. (it could have been an old fuse or a surge that caused it to pop)

Fuel pump - using a reasonable multimeter check the volts at the pump with with the engine off and on - the only difference should be the charging volts from the dynamo.

Are you using an old loom. These deteriate over time (40/50 years). You could run a seperate cable to the pump to eliminate the loom.

Ignition Light - could be the dynamo (probably not though), Dynamo brushes (possibly), Control box(usually) or you have a short somewhere draining the volts.

 

With the aid of the circuit diagram try to eliminate certain areas.

 

Roger

[AlanT]

Wonderful original Lucas electrical fault-diagnosis manual avaliable and other Lucas stuff from:

http://www.vitessesteve.co.uk/Other-manuals.htm

 

Red light flickering on when at idle is normal. You cant blow a fuse with a short at the battery end.

 

The fuse was probably blown when you turned the ignition key to start. The starter-solenoid draws a heavy surge current. Fuses do actually age and can just "give-up" under a strain.

 

Most likely the new fuse will fix it. Carry a few spares in case it goes again. If it does my money is on the starter-solenoid.

 

Al.

[MilesA]

Thanks for all the prompt guidance and pointing out the potential culprits!

 

I do have a wiring diagram and so step by step it will be and a chance to play with the multimeter I bought recently.

 

The loom was new when car was rebuilt about 2 years ago so think that is probably OK. The fuse probably went in at the same time.

 

The red light seemed to be glowing when motoring rather than idling which is why it caught my attention.

 

Raymond thanks for the link to Cox - great new photo of your car too.

 

Al thanks for the reference to the manuals - amazing what is online.

 

I have been thinking for a while that I need to establish a base line of understand about how car electrics work and what components like the control box, starter solenoid, etc., actually do and how it all interacts. If anyone has any ideas on that just let me know. My initial knowledge of car mechanics came from a Ladybird book when was a boy (seriously!) - I wonder if they did one on electrics as a starting point...

 

Miles

[littlejim]

From out of the left side of the field.

Had a friend with a periodically/intermittent glowing ignition light in a Datsun after a posting to Darwin.

The first Auto electrician gave him a list of all the items in the charging circuit that needed replacing and told him he was booked out for a month.

The second auto electrician walked off halfway through the explanation of the symptoms.

He came back with a new light bulb for the ignition light and replaced the old one, patted the friend on the back and went back to work.

The light worked normally after that.

Edited September 23, 2012 by littlejim

[MilesA]

littlejim - that could be the first of my step by step analysis!

 

Miles

[Mike Graham]

Recently saw these posted on another forum. They might be helpful to you and others.

 

http://www.sabra.be/GB/Tecnics/RB106.htm

 

http://www.worldphaco.net/uploads/REPAIRING_THE_STANDARD_RB106.pdf

 

Cheers, Mike

[AlanT]

What does the ammeter say when the red light is glowing? Should be a bit negative when at idle and go positive when running.

What does the ammeter do when you are running and then put the lights on?

 

Dynamo/regulator/ammeter is NOTHING LIKE a modern alternator/voltmeter set-up.

 

The red light is fed direct fro a contact WL on the regulator which closes when the dynamo is not generating enough current. A slippling belt might be one reason.

 

You will find full description of the regulator principle on Steves website somewhere.

 

Al.

[MilesA]

Mike - thanks for those links.

 

Al - Once everything had settled down (but I thought there was still a bit of glow in the red light) I checked the ammeter and it was on the right of centre ie positive. When I put the lights on it moved further right ie more positive and dropped back when I switched them off.

 

The car has an alternator and the belt should be quite tight as I did tighten it earlier in the year - no electrical reason for doing so, it was squealing at the time as it was a bit too loose. I will add checking this to my step by analysis.

 

First thing will be to see if the problem replicates itself. Unfortunately, I only get to the car every couple of weeks for a few hours so may be a while before I report back but I appreciate all the further thoughts.

 

Anyway, plenty of reading in the meantime from Steve's site and Mike's links!

 

Miles

Edited September 24, 2012 by MilesA

[AlanT]

If you really do have a altenator fitted instead of the original dynamo I should just ignore the red-light. These were fitted because dynamos dont genearte much at slow speed. So you need a warning that your battery is going flat.

 

Alterators were introduced to overcome this problem.

 

Al.

[MilesA]

Al - Thanks, it is a constant learning curve as an owner of one of these cars!

 

Miles

[Richardtr3a]

The only answer to the cut out problem is to send it away to Cox automotive who will overhaul, clean and adjust, so that all you have to do is connect up. I suffered a number of rubbish new ones until they overhauled mine. Since then there has been no problem and I have a stock of overhauled units in my garage in case the specialist at Cox retires. The first one was installed and I have never looked back.

 

Good luck