Electrical problems

[kch]

Very typical, one week before holiday the problems starts.
The electrical power comes on-and off, it seems like it is the electrical main switch (the one by the battery). Maybe bad connections inside the switch. I have checked all the terminals, and they seems ok. Should I just replace the switch, or is it an idea to dismantle it. Could not find the switch in A-H spares parts catalouge.

 

[john_j]

Are the cables long enough to bypass the switch? Undo the cables off both sides of the switch and put them both on the same side(or join them together with a nut and bolt and insulate them well.
If the problem goes away, then it's the switch (or one of the connections was loose).
Does the power go off for long enough that you can put a multimeter on both side of it and see if the power is getting through?
If you don't have a meter you can use a lightbulb and some wire.

Another thing to check is earth leads - they tend to corrode on their fixings, looking at them and saying 'that looks OK' isn't enough - you need to check them electrically, or undo them, clean them up and put them back on.

 

[AndrewMawson]

When my switch failed, it was initially slightly temperature sensitive - it would work fine first time or two, then after a run it was open circuit.

When I opened it up, the two stud contacts had worn down to just below the surface of the moulding. They could have been recovered by cleaning up with a file, and putting a thin washer behind them to bring them back up slightly proud of the moulding.

As a new replacement was to hand (good old eBay!!) I infact replaced it.

 

[Dave Russell]

IMO, the basic problem with the switch is that the spiral spring which maintains contact tension does not have enough tension & is vulnerable to losing tension with heat. A very poor design.

If the moving contact bar ever gets hot due to high contact resistance caused by dirt or corrosion, the resultant heating when it is carrying current causes the tension spring to anneal & lose tension. Less tension causes MORE resistance - heating - spring annealing - contach burning, until the switch fails. Cleaning the contacts and/or setting the terminals higher will only help for a little while unless the spiral spring is replaced with a new one. I believe that even a new switch is questionable & only a matter of time before it fails. I have tried stretching the spring & retempering it, which works for a while, but I wouldn't trust it.

A related problem is that when the spring gets weak, the switch no longer holds exact detent index position & the small terminal that is supposed to ground the points side of the coil when the switch is turned off, intermittantly grounds the coil when not intended. This means that 'if" you put both large wires on one terminal to bypass the switch, they should be put on the large battery terminal, not on the ground terminal. Since there are two large terminals & one small terminal it would be easy to get the two reversed. Make sure that the doubled up connection is on the original battery side terminal of the switch.

Mysterious cases of ignition cutout can be cured by also disconnecting the ignition ground wire at the switch & securely insulating the end.

This all being said, if you absolutely have to have a battery cutoff switch, there are several aftermarket switches, intended for race cars & boats, that are of much higher quality & cost less than the original failure prone device. A marine supply store can supply a good switch.
D

 

[tahoe healey]

In an emergency I used some baqttery jumper cables to go from the battery to the "other" post on the switch thus by passing the switch. Try that and see if you still loose power as you did before. There is an Ebay seller who sells a nice looking replacement for about $35.00 US. The knob looked great but not exact (a little taller). I pulled the C clip on the back and replaced the knob with the old one (exact fit).

 

[vette]

Karl, I decided that the small ground wire that runs from the ground side of the cut-off switch up to the distributor just wasn't necessary, so before it caused me trouble I just cut it off at both ends. Of course I'm not concerned with winning any concours shows. Without this wire, you can use any of the aftermarket switches as was said before.
Dave, /ubbthreads/images/graemlins/cheers.gif

 

[Michael Oritt]

[ QUOTE ]
Karl, I decided that the small ground wire that runs from the ground side of the cut-off switch up to the distributor just wasn't necessary, so before it caused me trouble I just cut it off at both ends. Of course I'm not concerned with winning any concours shows. Without this wire, you can use any of the aftermarket switches as was said before.
Dave, /ubbthreads/images/graemlins/cheers.gif

[/ QUOTE ]

Just today at Conclave one of our Capital Area AHC members was towed back to the hotel--his car had mysteriously died while out for a ride. After an investigation revealed there was a spark at the points and none at the plugs the suggestion was made that he cut the white/black wire at the coil--Problem solved.

IMHO having this wire in combination with the always-suspect kill switch is an invitation to sudden failure.

 

[Keoke]

HI Mike hope you are having a good time.I do not understand how they could have a spark at the points but none at the plugs because a ground fault on the black and white wire shorts the points to ground.??Separating the Black/White wire at the coil and placing it back on with a separate connector allows testing this circuit or rendering it inoperative without cutting wires.But it does seem to be a bit of a nuisance.---Keoke

 

[anthony7777]

oh that wonderfull master battery switch,and so close to were we put our fuel in,and so close to the fuel tank [rear end colision]i sometimes feel im driving a pinto,does anyone realy need this THING!and yes the marine types are far superior 20-30 bucks depending, they also have a selector type if anyone wants to run two batts,a little more expensive.

 

[Keoke]

Amazing init been back there for over 40 years and no serious problems.---Keoke