• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Electrical Trouble Shooting

Share this page

S

SaxMan

Darth Vader
Country flag
Offline
When you're trying to track down an electrical gremlin, is it okay to have the key in the "run" position, even through the generator light is full red? I also have an external 12 volt power supply with alligator clips. Could I troubleshoot using the external power supply hooked up to the wiring harness?

I have two minor electrical issues, that I'd like to check them out. Issue #1 is no backup lights when reverse is engaged. The bulbs appear to be intact. I'd need to see if there is power coming down the line when reverse is engaged with my multimeter. It's not a huge deal to be without them. There are certainly far more important lights to have working, but my obsessive compulsive side gets annoyed that they don't work.

Second issue is the blower fan doesn't always toggle "off". It will power up in the off position, and I usually have to toggle the switch a couple of times for the blower motor to stop. When I do go to the "on" position, the blower motor works fine. I'm guessing either a dirty contact, or the switch has just worn out after almost 45 years.
 
Leaving the key in the on position causes current sometimes to be going through the points and they in turn will have a short life if engine us not running. At least that is what I've heard in the past. Switches, most of them can carefully come apart. Take a look on Gerard's web site. There used to be pics of a heater switch I took apart years ago on Bugsy and put vack together after contacts got cleaned. There was a dog bone shaped brass contact tgat after the green was removed was as good as new.

Reverse lamps there here is a switch on the tranny that is engaged when you shuft into reverse. Take shift cover off and you will see a set of wires visible that go to a switch that is on the right towards the front of the tranny that you can reach. Switch simply screws out with a wrench and there are two wires in a loop. Tranny in reverse, button is pushed in by shifter and spring loaded switch completes the circuit. Get your meter hooked up turn switch to on and see if you are getting 12vdc coming down the wire.
 
I had heard the same thing about leaving the key in the on position and wearing out the points, Baby Blue was converted to a Pentonix ignition system, so no points to worry about (although I'm still running a generator versus an alternator....maybe an upgrade down the road).
 
Pertronix can burn out if key is left on.
 
As Drew said, leaving the current flowing through a Pertronix (at least the original Ignitor module... not Ignitor II) is worse than leaving the current on with points. The module can overheat within 3 to 5 minutes causing it to fail. Regardless of whether you have points or electronic ignition, disconnect the wire connected between the distributor and coil (-) to break the circuit and stop current flow. Just remember to connect it back when you are done or you will be confused when the engine won't start.
 
Hence the reason why I wired in a mini DPDT switch that send power to the radio and XM radio. I mounted to lower dash bracket via a 1/2" hole. Outlet is fused and in one position power fed from ignition switched source when key is turned on. In the other position power comes direct from battery via solenoid hot wire. So if I want to listen to tunes while working in the garage I simply flip the micro swich on and tunes without worrying about burning out points or electronic ignitions.
 
All the above works to avoid either burning up the points or the Pertronix. What works for me is to take the leads off the car battery and substitute a small 9 volt battery with an inline 5 amp fuse. That way if a short does develop during troubleshooting the fuse blows, and it is easy to replace with no hot, burning smell associated with the wire harness self destructing. Scott in CA
 
An even better idea.
 
Back
Top