The Stovebolt Site Forums The Shop Area The Electrical Bay I think I have a short in the starter...

Left the GMC sitting for a few days to find the battery completely dead. Tried to charge it but my charger kept kicking off. Used my jumper box to start it. When I disconnected the starter box the engine stopped. Took the ground off the battery and it charged right up. Wanted to get it running long enough to get it inside to work on it. I've always heard that if the engine won't run when you disconnect the battery there is a problem with the alternator/generator. Thing is.... I noticed that when I connected the battery even with the key off, I was hearing a click. I took the positive wire off the generator but still heard the click. Found the sound to be coming from the starter. So..... opinions are welcome before I start taking stuff off......
Thanks!

Sounds like your ignition switch or solenoid is defective

I agree.... but I started the truck and pulled the positive off the post on the starter and the engine died..... I'm gonna replace them both. Thanks for the reply.

Randomly replacing parts until you find the defective one gets expensive. Especially if the defective part damages the new components as you replace them. Best to find the problem before replacing parts.

I wouldn't quite call it randomly replacing parts. The starter and the generator are very old and I'm sure are going to fail before too long so replacing them is part of what I figured in the cost of getting it into shape. Is there something else that could possibly ruin these two components if I install them? It has a new voltage regulator on it and the only other thing I can think of is a short in the wiring somewhere but I would think that would burn some wires or blow a fuse. Appreciate the input.

No sense beating this dead horse, Cletis. "My mind is made up- - - -don't confuse me with facts!"

Removing a battery cable to check a charging system is almost guaranteed to create problems, even if they didn't exist beforehand. I've seen voltage spikes of well over 100 VDC on an oscilloscope when a cable is disconnected with the engine running. There are much better ways to check for proper charging system operation.
Jerry

Remove the starter and bench test it.

I've got them both off and will have them checked out. I actually didn't remove a battery cable from the battery. When I disconnected the battery booster I started the truck with it immediately quit. I did however take the positive off the starter while it was running. Will that also cause damage to the system?

Anytime a charging circuit is interrupted the generator or alternator tries to overcome the resistance created by the open circuit. That makes the voltage spike to unreal levels, at least momentarily. If anything like a solid state circuit, or even a low-amperage fuse gets hit with the voltage spike it will burn out. Since electric current travels at approximately the speed of light (186,000 miles per second) it's impossible to disconnect and reconnect a circuit fast enough to beat the spike. Generators don't get damaged as often as alternators, but it's still possible to trash a regulator by doing the cable disconnect thing. Just don't do it!
Jerry

Part of the problem is that the generator is still for a 6 volt system. Having it rebuilt to 12 volt specs. Gauges don't work either.... probably fried them when they changed the battery and regulator to 12 volt. I'll take it a step at a time. Thanks for the heads up on the battery interruptussss.

I'm just following for the learning, SoundBiscuit, but have you had the battery tested?

Brad

I am also curious on this as my battery seems to drain down when sitting below 10 volts.

voltmeter shows charging at 16 when running

16 volts is way too high- - - -it should be 14.5 or a little more, max voltage against a fully charged battery. The high voltage has probably damaged the battery, which is now unable to hold a charge. Is it possible to check the electrolyte level on your battery? If so, you will probably find it way low, with the tops of the plates exposed. Find out why the voltage is too high- - -probably a wrong regulator setting if it's adjustable, or a shorted solid state regulator if you're running an internal-regulated alternator. Either way, you've probably got a cooked battery. Find and fix the charging problem before installing a replacement battery, but be aware that a properly-charged battery in good condition is necessary before you can make charging system voltage measurements that mean anything.
Jerry

Every thing that Hot Rod posted about the charging system and the battery is good stuff. About the starter...it was the OP first question, I might have missed something( I do often). So here I go...2 bolts a cotter key and a cable are all that you need to get the starter out. Not much tougher than the battery. Get it on the bench and look at it. Pull the snap cover off, are the brushes good(hint: 1/4 inch left is not good). While the cover is off, turn the starter. Can the armature move? Around is good, back and forth, not so much, and, up down is not good( worn bushings). Is the commutator clean? Smooth? Shiny? No? It is 60 years old get it refinished. Look at the windings on the armature. Any signs it has burned, got hot or has broken wires? Get it refurbished. For those brave folks, 2 more bolts will let you take it apart. Some rubber bands will hold the brushes up or you can take the holders out(a couple of screws). It is a simple assembly so don't be afraid of it.Clean and inspect. Look at the field magnets. Rubbing(shiny spots)? Bushings are gone. Look at the wires, crumbly insulation? Time to get it refurbished. No spring cover? It will have dirt(not good) needs to be cleaned. Find a cover for it. Shorted starter is not common, open is. A good look at the switch(again 2 screws) will tell you a lot. Cardboard insulator..is it good or crumbled? Switch is not expensive. Look at the bendix(sliding gear part) still have teeth? are they chewed up? You get the drill. Look at the link that moves the bendix. Is it bent? Still have 2 round feet that engage the bendix. This is all covered in the manual, and none of it is hard to do.

after lots of head scratching trying to solve my problems with battery going dead and engine refusing to start on my 49-3600 only to have it start up and run fine after being towed home I discovered the PO had used a couple of sheet metal screws to attach the voltage regulator to the firewall after replacing them with the proper mounting screws she starts every time and runs like a top its a 6 volt neg ground system also had to replace battery cables with heavy gauge 6 volt cables PO had lighter 12 volt cables now my truck is very reliable I wouldn't hesitate to drive her anywhere hope this will save someone the aggravation that had me questioning my sanity till I figured it out looking forward to warmer weather so I can get out on the road again

Yep.... I have a battery tester and it tested ok.

Appreciate all the info. I pulled the starter and am replacing it with a new one. I also pulled the generator and am having it upgraded to 12 volt. I have an old school generator/alt/starter shot here close by and he is also going to go over the starter for me. I'm afraid someone before me threw a 12 volt regulator and battery in this truck, changed a few light bulbs and let her rip. I'm pulling the dash to check the gauges, nothing works except the speedo. I'm guessing they are all fried.

What are the results of the battery test? You should be able to load the battery to 1/2 its cold cranking amp rating for 15 seconds and have at least 9.6 volts with the load still applied. For instance- - - -a 600 CCA rated battery needs to be tested at 300 amps for 15 seconds, then check the voltage.

If it passes the load test, check the specific gravity. The full charge SG should be at least 1.265 with a max of 1.300, and there should not be more than a.020 variation between cells. Does the battery pass both those tests? If that hasn't been done, the battery has not been "tested".
Jerry

I don't have the equipment to test the battery to that degree. I have a battery tester that puts a load on the battery and tells you whether it's good or not. Shows good. Good to know how to properly test a battery though. Thanks.

We used to call those 100 amp fixed load testers "battery sellers". When a customer would come in with a weak or partially discharged battery due to a charging system malfunction, putting the "tester" on the battery was a good way to sell the customer a battery, along with whatever else it took to fix the original problem. Some of the shops in town would even recharge the "exchange" battery, spray a coat of flat black paint on it and sell it as a "rebuilt" battery. I was never willing to stoop to that level of so-called repair work!
Jerry

I got the new starter today and the generator is in the shop getting a rebuild. I just bought the battery about 6 months ago so if I find out it is/part of the problem I'll get it replaced. Both the generator and starter needed replaced/upgraded. Rather do it while the weather is lousy than when I want to be out driving. Not going far with this thing in the winter.... doesn't have a heater. Thanks for your help....

Just got everything replace. Realized the popping is coming from the voltage regulator. I know, should have done more testing before replacing but I had planned on replacing both anyway.

Is this "popping" the same "click" you were hearing originally?

That would make sense.

Brad

Yep, afraid so. I was by myself originally and thought it was coming from the starter but I had a friend with me after I installed the starter and generator and it is definitely coming from the regulator.

....ok.... wasn't definitely coming from the regulator. Seems like my problem has been a bad horn relay. That was what was making the clicking sound and draining the battery. Disconnected the hot to the relay and problem solved. Lots of good info here... thanks for the help.