Wiring Help

[Paul Storrar]

1954 R -Type Radford Countryman B268WH

I am hoping the members will be able to help with my first 'fail to proceed'.

A week ago, I was returning home in the R-Type and went over a speed bump....the car cut out and smoke started coming from the top of the dashboard!
I switched off, grabbed the fire extinguisher.... but the smoking stopped fairly quickly fortunately.

No fuses had blown, and the smoke had come from a wire to the button for an electric windscreen washer pump fitted on the board between the windscreen surround and the dashboard.
This wire was attached to the regulator terminal A1.
I am presuming it may have shorted against the bodywork as it passed through a hole in the bulkhead with no grommet and so may have rubbed through the insulation - the speed bump being the last straw.
Having spent too long going cross eyed over the wiring diagram, I can't work out why there is no voltage getting to various circuits - the car won't start as there is nothing getting to the fuel pump or coil.

I have followed the wire from the regulator into the back of the switch box (which I have removed, checked and all appears ok).
It seems that the brown wire from the A1 terminal on the regulator, where the rogue burnt out wire connected, goes into the switch box via the ammeter.

What do you think the problem could be?

There is power to the main fuse, and the first two fuses in the distribution fuse box, but not the others (so no side/headlights, fuel pumps, coil, blower motors, wipers, etc). The starter motor works.

What would an overload from terminal A1 on the regulator to earth cause?

Would a damaged ammeter cause these symptoms?

Any help would be much appreciated.

Best wishes,
Paul

[John Robins]

Is there continuity across the ammeter? Since power for all the items that you mention as now dead are receiving their power by way of the ammeter, if I read the diagram correctly, it seems that component might be a good place to look. You say it doesn’t work, is this since the incident or for longer?

Cheers
John

[Christopher Carnley]

Have you checked if the actual main switch box is passing current?

Has the shorting welded the internal contacts together?

[John Robins]

Aided by Christopher’s thought, do the Parking lights work? If you look at the switch box diagram, they use different contacts.

Cheers
John

[Paul Storrar]

Thank you John & Christopher

The parking lights do work and the panel lights will come one too when the switch is in the PL position.

I took the switchbox out completely and cleaned/checked all the contacts and all appears to be working as it should (and passing current).

The ammeter was working fine before the 'speed bump smoking' incident - but now doesn't. The fuel gauge is also dead. I think I need to extract that from the dashboard too.

I will do some more testing, but from memory I was getting continuity between the chassis and all the terminals on the regulator - which seems odd. Also continuity with some of the terminals in the fuse board. (The car is negative earth).

[John Robins]

Ammeter working fine, everything else working.

Hit speed bump, burn out ammeter?

Ammeter duff, nothing works.

Were it me, I would check the ammeter for continuity before I did anything else.

Just a thought, why is it -ve earth?i
Cheers
John

[Paul Storrar]

Having just extracted myself from the yoga position we have to adopt under the dash, testing the ammeter, there doesn't appear to be continuity.
I haven't taken the gauge cluster out of the dash before - can I just detach the oil pressure and coolant temperature connections easily without causing any issues?

[John Robins]

Don’t do this without agreement from somebody else as well, but, my thought would be to bypass the ammeter by joining the two connections with a piece of cable containing an in-line fuse holder with a 10 amp fuse in it, and see which circuits come on. If you get the ignition and fuel pumps back, then you think about dismantling the dashboard. If the fuse blows with everything switched off then there is a short to earth somewhere.

I would try this on my own car, but only with the greatest caution. As an expedient measure, you could at least move the car if my theory is correct.

Cheers
John

[Stephen Blakey]

Just to say John's suggestion sounds good to me.

Bear in mind that 10A is only 120W, so headlamps plus sidelights may blow it. I suggest you test those last.

[John Robins]

Thanks Stephen.

The low value fuse idea was to protect from anything drastic happening if there was a short somewhere. There would be the option of upping the fuse capacity before trying the headlamps if the aux circuits were ok. The other trouble, of course, is ancient wiring that may have crumbling insulation although that in the picture looks passable.

It seems that the rogue wiring to the electric washer pump may have put the ammeter into the rôle of fuse.

Cheers
John

[Stephen Blakey]

Hi John. That sounds like a very plausible hypothesis. That must have been a pretty heavy duty cable to the windscreen washers, to kill the ammeter? Maybe the ammeter was already somewhat past its first flush of youth, and this was the final straw?

[John Robins]

Perhaps Paul may enlighten us after he enlightens his headlights!

Cheers
John

[Paul Storrar]

Thank you John and Stephen - very helpful.

I have bypassed the ammeter and...... the car came back to life! Fuel pump ticking, power to coil and headlights restored. It must indeed have blown the ammeter, depriving the connected circuits of any power.

A moment later the individual fuse to the circuit for the heater blower, demister blower and windscreen wiper blew, so I removed all the switches from the dash, cleaned the contacts, checked wiring, etc and replaced.

That done the fuse hasn't blown since (and a test of the heater motor switch showed the resistance on the slow speed setting was very high, so a squirt of contact cleaner and some vigorous back and forth rotations seems to have restored the correct resistance and I now have a two speed heater).

My remaining job is to extract the ammeter from the gauge cluster, which I hope to tackle later this week. It looks like I can disconnect the oil gauge at the back, but have to draw the coolant temp connection out through the bulkhead as it is a sealed tube.

Does anyone have any suggestions on a company that can repair the ammeter? I have found Speedograph Richfield Ltd recommended on the Australian RR forum.

Another question - where would be a good place the wire the previously rogue electric windscreen washer motor into? The 'country' horn (presumably a Radford fitting?) is wired into the main fuse circuit in the fuse box - which I think is incorrect, but it does mean the horn works with the main switch off. Perhaps a suitable windscreen washer motor connection would be the cigar lighter/radio circuit.

The wiring does seem in good condition, but it has been good to give the connections a thorough clean up. The only deterioration seems to be to the rubber protectors on the connection crimps.

[John Robins]

Thanks Paul.

Any circuit that is protected by a fuse, and under control of the main switch. The cigar lighter/radio circuit sounds good, or the pre-switch side of the wiper circuit. Make certain you are after the fuse!

Sorry I can’t help with a repairer for the ammeter, perhaps the small ads in a classic car mag might offer some ideas.

Cheers
John

[Stephen Blakey]

There's very little in an ammeter. From memory it's just a hefty coil and a magnet on the end of the needle. You may be able to fix it yourself.

It may have been that one of the connections to the coil had become corroded. That would then have been the location of a minor explosion when the short circuit occurred, much as a fuse would blow as John suggests. I suppose the difficulty of repair will depend on the extent of the damage.

I would go to the workshop and have a look at one for you, but the rain is hitting our windows faster than it can drain away so it's a bit like sitting in a submarine and the prospect of stepping outside is about as appealing as it would be in one of those.

[Nicholas Simons]

An decent ammeter is simply a voltmeter wired across a very low resistance shunt resistor. The voltmeter measures the volt drop across the resistor, which is proportional to the current flowing through it. The shunt resistor in the ammeter may have suffered a loose connection, resulting in all the current going through the meter winding and blowing it up. Have a look inside. If you are lucky, the fracture of the meter winding may be somewhere accessible and repairable. If so, don't forget to check the shunt connections.
Cheap ammeters are of the 'moving iron' type, as reported by Stephen above.

[John Robins]

https://www.cecbrighton.co.uk/Joseph%20Lucas-%20Ammeters,%20Battery%20Parts%20%20Etc%20Section%20%27B%27.pdf

[Christopher Carnley]

The best firm to send it to is Speedy Cables down in Swansea.
These moving iron types are quite straightforward to repair.

[Paul Storrar]

Thank you all for your very helpful input. I have extracted the ammeter and opened it up, and as you thought, the coil has burnt through.

I can't see any sign of a resistor - it looks as if all the current must flow through the coil.

I have ordered a replacement coil and will solder this in place and gradually reassemble the car.

It has certainly been a wiring adventure over the last few weekends - and fixable for £10!

[John Robins]

Thanks for this.

Cheers
John

[Nicholas Simons]

Thanks for the photos. That is a moving iron ammeter so won't have the shunt resistor. You can easily make a new coil with a piece of thick copper wire of the same gauge and just the single turn. Cost, less than 10p.

[Stephen Blakey]

I had the same thought. The resistance of the copper won't affect the magnetic field, so a close approximation would do.

It's surprising that was the weakest point of the circuit. I had expected it to go at a connection where there would be resistance.

I fitted a battery switch to my MKVI. It's a Lucas, with an old-school black knob which sticks up through the floor to the side of the drivers seat. This was suggested at one of the RREC seminars. The idea is that if the electrical smoke starts to escape from the wiring, the whole lot can be switched off quickly.

Thanks for keeping us updated, Paul.

[Christopher Carnley]

I took a complete one out of surplus roundel, but could not upload pictures.

It says "SMITHS" on the glass cover, but it is a basic "Lucas".