need help tracking down a short

[GRU]

Ive been having trouble since spring with something draining my batteries down in less than a few hours to where the truck wont restart. The alternator tests good at autozone and i recently replaced the voltage regulator since it was bad. I thought maybe it was keeping the alt excited but evidentally that wasnt it. A few suggestions have been the alt is bad even tho its charging and possibly glow plug relay hanging up. I havent had much time to dig into it. Kinda looking for good suggestions to try first. Thanks.

 

[Shadetreemechanic]

You can isolate it by hooking a multimeter up to the battery posts in resistance mode. With the radio fuse pulled it should show an open circuit for the whole truck. If not then go through each circuit pulling fuses until you find where the drain is. Several times I have seen that a worn ignition switch will sometimes leave a portion of the truck live with the key off causing a drain so an early check would be to wiggle the key if you show a drain on your multimeter at the battery post.

 

[franklin2]

Most vehicles have normal small drains. These usually add up to something less than .07 amps though. The best way to check for this is to take the driver's side battery negative cable loose and lay it on a rag, and then take the passenger side battery negative battery cable loose, and lay it on a rag also. On the passenger side battery negative terminal on the battery, clip a testlight lead onto the battery terminal itself,, and then touch the probe onto the negative battery cable end laying on the rag. If the testlight lights up bright, you do have too much drain.

You can then pull fuses one at a time till the testlight goes out. Make sure the door is shut when you are doing the tests, the domelight will be a drain. If none of the fuses get rid of the drain, take off any added wiring on the + terminal of both the battery(feeds for amplifiers, etc) and see if it goes out. If it doesn't, then take the large output wire off the alternator, and if the light goes out, then the alternator has a bad diode in it causing the drain.

 

[GRU]

Ok that is whats been suggested to me elsewhere too so thats where ill start! I hadnt heard of the ign switch tho. Thats also quite possible. Just sucks cuz i havent driven it 200 miles yet this summer cuz i cant let it sit once i get somewhere. Havent had much time with my dually project consuming all my time. Thanks guys!

 

[freebird01]

on my orange truck i had that happen.... ended up being something bad inside the steering column like a rubbed wire or something....i swapped the columns and the drain went away

 

[dgr]

I'm sure shadetree means the battery cables and not the posts as measuring resistance with power applied lets the smoke out of meters. A life time ago the shop I worked at had a meter we would use as the test light is described above. An ammeter in a fancy box was all it was. You connect it and isolate circuits until the draw goes away.

 

[franklin2]

Yes, you can use a ammeter, most digital meters can be set up for measuring amps, you usually have to move the leads around on the meter. Most early vehicles like ours should have a very low reading, probably around .01-.02 amps. The newer the truck, the more stuff it has on it and the more draw. I am sure a truck with a E4OD computer will have a little bit more.

If you find you have no drain, then your batteries are probably shot. Mine was acting the same way as yours, but after I did the drain test and found there was no drain, I replaced both batteries and all has been good for about a year now. When mine was acting up, I could jump it off in the morning, and it would be fine the rest of the day, but once I left it overnight, it would barely turn over the next morning.

 

[sassyrel]

didoes can go bad,three ways.. burn open,,short to ground,,or short to reverse the current.. if they short to reverse current,,it will charge,,and work just fine running..but as soon as you shut it off,,the back draining of the batterys begins,,and depending if more than one are this way,,is the amount of draw...

 

[Shadetreemechanic]

I'm sure shadetree means the battery cables and not the posts as measuring resistance with power applied lets the smoke out of meters. A life time ago the shop I worked at had a meter we would use as the test light is described above. An ammeter in a fancy box was all it was. You connect it and isolate circuits until the draw goes away.

Thanks.... yes cables.

 

[GRU]

well the batteries are only 2.5 years old. and good napa ones at that. if i charge it up and leave it set with the neg cables unhooked they hold charge. so im ruling out the batteries. now however i have a napa deep cycle thats also the same age in my gooseneck to run the hydraulic ramp and it will not hold a charge anymore... i have two days to get my dually put back together before it goes to my mechanic buddy for a 3.55 gear swap and get the timing set. once its out of my shop Blue will come in and get checked out thoroughly. thanks for the help, ill post up the findings.