Electrical Irritation...

[lear]

I know this needle in haystack stuff trying to source electrical failures but just wondered if these symptoms chime with anybody. So:
1 car sitting for ages, battery not holding charge so replaced
2 car runs fine when jumped - ammeter gauge indicating high positive
3 when I turn the key off and take it out, the parking brake light and oil pressure lights etc stay on (I have a separate kill switch as well)
4 finally, brake lights stopped working - all others fine

I haven't checked anything at all yet except the brake bulbs. Any ideas greatly welcomed if these symptoms suggest anywhere to start. Thank you

[mrzigazaga]

Hi Mate...Not 100% as regards to the 350 but have you checked the output of the alternator when the car is running?..I wouldnt rely on amp/voltage gauges in car..A good indication is if the battery light/Ignition light is staying on when running the car..This will suggest a poor charge from the alternator..When my brake lights stopped working it was the brake light switch which is normally situated at the top of the brake pedal..They sometimes stick and need a clean and a small amount of electrical lube..But should be cheap enough to replace if need be..Hope this helps...Cheers...Ziga

PS:As regards to lights staying on..maybe a fault/short somewhere and thats whats draining the battery?..Faulty ignition switch?...Relays?..Not very electrically blessed im affraid...

Edited by mrzigazaga on Sunday 31st March 12:03

[Danny Hoffman]

lear said:

3 when I turn the key off and take it out, the parking brake light and oil pressure lights etc stay on (I have a separate kill switch as well)

Do you have a radiator fan override switch fitted with a warning lamp? When I fitted mine, very occasionally I had these 2 lights stay on. I'd flick the switch on and off and they would extinguish.

I lived with it for years and then finally decided to sort it, a diode in the warning lamp feed cured all.

Danny

[superwedge]

check all the earths on car,

[ElvisWedgely]

The best way to fix an electrical problem is by using elimination and some trial and error. You probably have a combination of several electrical faults. The brake lights not working for instance is probably the brake light switch at the top of pedal. Check to see that the switch is working etc. The parking lights could be to do with the switch on the steering column or the light clusters themselves. You have to check these and eliminate. Check the earths as you go along. Now that you have replaced the battery, check that the alternator is charging properly. To do this the car has to be running and by using a multimeter between the battery terminals you should have a reading of around 14.5v. Lastly, check there is nothing draining the battery overnight. Check all devices and if necessary fit a battery isolator. It's no good having a good battery and a good charging system if something is draining it overnight..Boot light, stereo, alarm system etc.

Tony. TCB.

[Rockettvr]

To check for battery drain disconnect + terminal of battery and connect an ammeter in line ie; between + side of battery and + battery lead - this should read 0 or very close to it with everything turned off. If not then start pulling fuses until the current reads O. This will tell you which circuit is pulling the power.Its then a case of working your way through that particular circuit until the problem is identified. AS Mr Wedgely says just be methodical and all should become clear.. I agree with Tony too as it sounds like several small issues not one big one. Good luck

[adam quantrill]

If you get stumped then it could be the diodes in the alternator. When one goes it can give a big battery drain and funny symptoms. Disconnect battery -ve, then try disconnecting the big alternator + wire (and insulate it with tape) and see if the symptoms go away when you reconnect the battery.

[RCK974X]

Can be hard to trace these kind of faults - I think the alternator diodes are a good suggestion.

My suggestion to add to the list is to make sure all your earth points are all sound - 'floating' earth wires can also cause all sorts of weird symptoms. Clean and check them, especially from the engine block. It could even be a faulty ignition/key switch, but not very likely I reckon.

RocketTVr's suggestion is a good one I reckon, tracing current flows is a good way to find faults, but you have to be methodical and check everything logically.

I tend to disconnect my battery when leaving the car sat for a while - it's 30 seconds well spent IMHO.

[lear]

Thank you very much for all your suggestions - really appreciate it. Good to see all the evidently great experience of wedge electrics! Will try to trace it tomorrow and see if I can persuade my wife that we don't really need to go out for lunch...

[Jack Valiant]

As mentioned already this is symptomatic of alternator diodes in the regulator pack on the alternator being toast fella. You can repair but to be honest just trade in for another alternator fella job done!

Chris

[ElvisWedgely]

If you suspect the alternator, these people are very good. They are in Elstree just to the North of London. If you take your alternator there, they will test it for you, usually while you wait, and if it's not good they recondition or exchange at reasonable prices.http://www.unit-exchange.co.uk/
I have used them before on several occasions and have been very pleased.

Tony. TCB.

[adam quantrill]

If you can use a soldering iron at all, then you can replace the diode pack yourself fairly easily. I got a Lucas equivalent one off the flea for a tenner and it took me about an hour - most of the work is fiddling with nuts and washers, hardly any electical stuff to do...

Edited by adam quantrill on Monday 1st April 12:38

[lear]

Thanks all - Zig first out of the blocks with the brake light switch - that is definitely the cause of the brake lights not working. Not quite sure how a spring with a bit of metal tacked on to it fails but there we go... Thanks also for alternator suggestions; looks like that also needs doing as I still have charging issues.

[jeff m2]

Set your voltmeter to 20V AC test between a ground and alt output, if the needle moves the AC is not being rectified to DC.
Diodes toast.