Troubleshooting electrical short

[cali_surfer]

It seems as if I have an electrical short on my '69. I installed a Painless wiring harness back when I restored this truck a few years ago. I've been having some funky problems, radio going off and on, turn signals slow to blink if at all, tach frozen at a specific RPM regardless of motor, etc. When troubleshooting electrical problems, and since the Painless harness has so many different circuits, can I put an electrical tester on each of the individual circuit fuses (showing ohms) to see what the problem is? Is that how its done? This happened Saturday night, blinkers started acting up, radio display went black, then tach froze. It was late, but I checked the battery voltage--was 13.7, went out of town Sunday and didn't even touch it, then today I just went outside and the voltage is 10.7....... so obviously there is some sort of issue I have to deal with.

[68w/sbc406]

i had a problem similar, my radio would turn off and on even with the truck off. what it ended up being is that my alternator would charge while it was running, but it also created a draw when it was off. i had taken it in cause my battery died and auto zone said it was fine. they dont have the ability to check it other than the fact that it is charging. once i took it to a shop they pointed out my problem and i bought a new alternator and didnt have the problem again

[Mudder]

I'd start out by just cleaning all the ground contacts.

[cali_surfer]

Ok, I just tried to start the truck....... it made this weird racheting noise I've never heard before. What's that all about. It wasn't the usual clicking sound of a solenoid when there's low voltage or a hot starter, but this weird racheting noise. Good heads up about the alternator, I'll definitely keep that in mind.

[Don R. Dodson]

Cali Surfer, think about it a minute. You say the radio comes on and off. Now lets see if I have this right. Is the ignition switch turned to the Accessory position or the ignition switch turned to the run position? If the ignition switch is turned off and the radio comes on you have something to work with. Only way the radio should come on is from the ignition switch providing the voltage to the radio. I hope you have a volt meter such as a multi meter. Remove the ground on the battery, and set the meter to DC volts on the scale high enough to read 12 volts. Now connect the meter with the plus side to the negative side of the battery, and the negative side of the meter to the battery cable that you removed earlier. You should read zero volts, unless you have a drain somewhere on the system. If you have a clock, disable the clock so that the clock won't be the cause of you getting a voltage reading. If you get a voltage reading then you have something causing a drain on your battery. You can isolate things by removing fuses, and any other suspect you can come up with in hopes of getting a zero volt reading on the meter. If you don't get a voltage reading, then an old electronics trick I use is to use the butt end of a screwdriver and tap things that might be causing a short condition, while observing the volt meter. If you see the needle move you are on the money. Maybe a shorted diode in the alternator is the culprit. Any voltage fluctuation can cause erractic behavior to such things as radio and turn signal flashers, and with a shorted diode it can cause your regulator to go banannas. With your engine running the alternator should be putting out around 14.5 volts to the battery if the battery is low and needs charging. If your battery is low, then check to see if you are getting 14.5 volts, if not, then suspect your alternator is defective or your regulator is messing with you. Purpose of the diodes in the alternator is to change the alternating current of the alternator to DC voltage for the battery to see.

~ Don ~

[70c10]

Cali- first off welcome back man!. I haven't noticed you posting much in awhile. Maybe you have a bad regulator. It might be that or like others said- a bad alternator. Good luck.

[cali_surfer]

I was trying to do some troubleshooting earlier today and now am confused. I checked the voltage of the battery and after I try different things, such as the turn signals, the headlights, etc. the battery's voltage goes down, but then slowly climbs back to what it was. Is this the function of its reserve capacity? In any event, I replaced the headlight switch and ignition switch. Still have the problem. My starter is acting up, I'm thinking of taking it back and getting a new one (it's under warranty). I wish I had the bucks for one of those slick gear reduction types. Is there a stock type starter that can be purchased at the autopart stores that is a gear reduction? I have a 153T flexplate. Since I'm having problems I looked at the turn switch. I was looking at the wiring harness connector and it appears as if 3 of the terminals may have been arcing between eachother. There were bluish marks on the crimped ends, and the crimped ends had some slop in the plastic harness. My low-buck fix was to coat where they might be touching with silicone, essentially potting it to insulate each connector. I'm letting it dry overnight and then going to see whats up. If that doesn't work I'm going to replace it, just trying not to since its $50.

[djracer]

I'm not sure how many tooth flywheel my 95 sub came with but it had a gear reduction starter. I'd check to make sure you have a good ground from the motor to the frame and the battery to the body!

[70c10]

Cali- this guy has mini starters cheap:http://cgi.ebay.com/ebaymotors/ws/eB...&rd=1&tc=photo

I got my turnsignal switch and adapter at the dealer for less than $30

[68w/sbc406]

what are the advantages of gear reduction starters???

[cali_surfer]

I swear, it hasn't been my day. I kept getting screwy readings from my multimeter. Well I borrowed one from a buddy and he was getting different readings......... turns out my meter is junk! Can't troubleshoot with a shot meter. Sheesh

[68w/sbc406]

Doh!!!

[cali_surfer]

I still have problems though, a dead battery and turn lights that don't work......... gonna give it another try tomorrow

[cali_surfer]

Well, I went out again today and tried to diagnose. I started from square one like you said Don R. Dodson, put the volt meter on the neg. battery cable and post. Sure enough there was voltage with the truck off. Isolated the radio by pulling those fuses first, then went one by one thru the fuse panel. I got all the way thru and still had a draw. I sat back and scratched my head. Well I forgot about my keyless entry and power door locks, removed those fuses from another part of the cab, still had a draw. Sat back and scratched my head again. After reviewing things I took 68w/sbc406's advice and checked out the lead to the alternator. Sure enough, there was some draw going to it. Took it off the truck and brough it to the part store, tested bad. Unfortunately I ran out of light today and didn't finish, but hopefully that was the problem. I still need to put my battery on the charger..... 10.1 volts, a little drained!

[68w/sbc406]

glad you got it figured out