35 PJ suddenly won't start

[Gary Vickery]

Chet
Thanks for the help.  I found that I had 4 guage battery cables, so I now have NAPA making me some nice new 00 cables.  Seemed like a good place to start.  I have been reading a book by Jack Steele - How to Find a Short, which has also helped.  This has been a real learning process, and I love it.  Thanks again!

Gary

[chetbrz]

Gary,

Electrical circuits in old cars though basic, can be extremely tricky.  Years of corrosion and wire insulation degradation added to the heavy current draw of a 6vdc system can result in hours of troubleshooting.  If you are working on the headlight ckts you have to consider the effectiveness of your ground points, the wire deterioration associated with the high beam switch.., especially if it is mounted in the floor.   Poor power and ground connections could appear like shorts or opens.  When in doubt, start with a known good point.  Remember every connection point adds to the overall resistance of any ckt.  Running a test ground wire from the ground side of your battery to the ground side of each component in question is a good way of eliminating ground issues.  Likewise running a voltage test wire from the supply side of the battery can do the same in eliminating voltage supply issues to the components you are checking.  If you are not sure about doing something like this.., attach an inline 15 or 20 amp fuse to your test wire to protect your car wiring against a mistaken connection.

I think high resistance is a big contributor to your problems.  Every connection in your car has the potential to add to your overall current drain.  Kirchhoff's voltage law states that the sum of the voltages in a closed loop will always equal zero.   If you are reading voltage on both sides of a working component in relationship to ground you are seeing resistance created by the component connection points.  The most common place to start is to ensure that your battery cables are the correct thickness for a 6 vdc system and that their connection to both ground and the circuit you are troubleshooting are clean and resistance free.  Never use 12 vdc battery cables in a 6 vdc system. 

It doesn?t sound like there is going to be a quick fix to your problem.  I would suspect that the cut out switch was installed because the car had some type of resistive short draining the battery slowly.   Probably a deteriorated wire harness point usually under the car near the high beam switch.  Most common cause of battery drain is the car?s clock ckt. 

Hopefully some of this might help you.  Good luck,  Chet?

[Gary Vickery]

Well, it appears I may have multiple electrical problems, not the least of which is an 80-year old wiring harness.  It turns out my battery wasn't fully charged, and it looks like it takes every bit of 6 volts to turn it over.  Now charged, it starts fine, but I still don't know why the battery was down in the first place.  I still have a short somewhere and must have not opened the battery cutoff switch overnight at some point.  I have removed the headlight relay from the circuit, and of course now have a very dim headlight.  In looking for the short, I noticed that with my test light I have power on the hot side of the brake light switch but also have a dim light (small current) on the other side of the brake light switch.  I don't see a brake light on, so I wonder if the switch could be shorted.  I think I will replace and see.  Maybe that is what is drawing my battery down.   I also noticed that the fuse at the ammeter gets hot to the touch when the lights are on, and that there is a hot spot on the headlight switch as well.  I understand that those hot spots could be signs of high resistance that is causing me a problem.  Any thoughts?

Gary Vickery
35 PJ

[chetbrz]

If you are reporting no headlights with a charged battery then you have an open ckt for sure.  The cutout switch is a good suggestion but after jumping that out you need to look for an open.  I am not familiar with your 32 but battery cables, posts, grounds, and fuses are a good place to start.

Good luck, Chet...

[32cabrio]

Remove the battery cut-off switch and connect the battery as it normally would be. Clean the battery posts and the cable ends. Check the grounds and make sure they are bright and clean.

[Gary Vickery]

Drove my PJ a couple weeks ago, started fine.  Suddenly, sitting in the garage, pushing the starter button does nothing.  Won't budge the starter.  Checked the battery with a multimeter, it was dead, so I charged it and it is holding a charge.  Still nothing with the starter button. No headlights either.  Thought maybe the starter switch, but it looks fine, and that wouldn't explain no lights.  Has a battery cutoff switch that I keep switched off all the time.  When I switch it on, and turn the key the ammeter shows a slight discharge.  With no lights or accessories, why would that be?  I must admit that sometimes I forget which way the cutoff switch should be, so I try it both ways to be sure. I cleaned up the connections to the starter post, not sure what to try next.  Any ideas?