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I have disconnected both negative battery post and checked dc voltage from negative battery post to negative battery cable and get 12.49 vdc. Am I checking this correctly? I have pulled each fuse and disconnected alternator and most connectors under hood with no change in voltage. I also checked for raw wires under body and at all lights. Having problems with batteries staying charged. Just replaced both batteries with Interstate Batteries. If I let it sit for more than a couple days without cranking it has to be charged. Any suggestions?
Take a pic or two of the top of your engine, and post. Need to see the batteries and terminals.
Also, you are going to need to measure amps and milliamps on your multimeter. See what the reading is between the terminal (negative terminal) and the disconnected battery cable (amp setting first, and then if it is too low to read accurately, then with the multimeter on milliamps setting). Post the results.
All accessories off, and I would disconnect the underhood light.
I use a 'fuse buddy' for draw testing. It's handy to leave it hooked up while I use my multimeter for other things.
If you get one, make sure it's not the 'heavy duty' version. You need the 2 decimal places for testing draw. It's not as accurate as your multimeter, but it does OK enough.
I also use something like this when I want to measure the power consumption. But as soon as you remove the fuse and insert the fuse buddy, you have "awake systems". For the parasitic draw measurement, the systems have to be "asleep".
I do the first test as follows (it works better with a helper):
-Vehicle is parked overnight.
-I loosen the negative terminal screw, but the terminal still remains on the pole.
- The negative terminal of the second battery is completely removed.
- Now I hold one measuring tip of the amperemeter from above on the center of the negative battery terminal, the other measuring tip I hold on the terminal clamp.
-Now I carefully pull the terminal clamp upwards, away from batt pole.
- Now I can measure the parasitic draw in sleeping systems.
I very rarely actually use it in place of a fuse.
I made an attachment with alligator clips with a fuse holder and install it inline as you describe.
I'm usually working on something with a single battery, so I cant fool them by keeping one in parallel. Most vehicles go to 'sleep' within 15-30 minutes, so I disable any door open switches (usually in the latch nowdays) and/or courtesy lights, disconnect battery, attach fuse buddy, then go have a sandwich. When I get done it's usually ready to mess with.
I do it a little differently than Hartwig because it's a pain if you disconnect a lead while moving things around. If we had one battery, Hartwig's method would be the way. Or Kbeefy's.
Remove the negative terminal from one battery post.
Install the ammeter between the terminal and the post.
Remove the other terminal from the post and isolate.
I do it a little differently than Hartwig because it's a pain if you disconnect a lead while moving things around. If we had one battery, Hartwig's method would be the way. Or Kbeefy's.
Remove the negative terminal from one battery post.
Install the ammeter between the terminal and the post.
Remove the other terminal from the post and isolate.
You need clamps on the ammeter leads to do this.
This is essentially the way I do it as well.
I am somewhat amused at the OP's lack of response. His profile showed him looking at the thread after a few responses were posted............................
I’m sorry for not getting back with all of you. I am disabled and sometimes I have to take a break because of my spine surgery. When I did get back out to my truck it wouldn’t start. So now I’m looking at the starter. Truck cranked and ran fine yesterday but this morning it wouldn’t7 turn over. 12.5 v on batteries. To my knowledge it has the original starter on it. I’ve had it since 08. Could bad starter cause a big voltage draw?
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Battery parasitic draw
