ABS module short?????
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ABS module short?????
I am new here but have used this site several times to help repair my truck and i say thanks..But i have been fighting a short in my 2001 f150 4.2l. I have hooked a volt meter to the neg battery post and it shows 12.5-12.6. So ihave unplugged all the engine fuses and found that the 50amp ABS when removed the volt meter drops to 0.03. So i put fuse back in and it showed 12.5 again so i unplugged connector going to the ABS module and the volt meter dropped back to 0. I replaced the ABS module/pump thinking it would fix it. It still shows 12.5 when plugged up... has anyone else fought this battle??? The baterry drains overnight.Any suggestions would be very appreciated..
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Hotshot
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From: St Louis
What other point are you measuring using the positive lead of the meter? A voltmeter has to have TWO connections, one positive, one negative. If it's on the load side of the fuse, it's supposed to drop to zero when the fuse is removed (open circuit).
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Yes I understand that I Was trying to isolate the shorted circuit. As you would do with a test light from neg cable to neg post. I have the circuit isolated but the abs module which I just replaced when plugged i I still get 12.5v on neg cable to neg post. I just about ready to burn it lol
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Thanks Dave, I even unplugged all the wire harnesses goining into the cab. There are three connectors on the driver side under master cylinder and 1 on passenger side. I can unplugg the ABS module then the reading drops to 0 then in a few minutes it will show 12.6-12.8 again from neg term to neg post. I have unplugged altenator,ABS module took all fuses in cab and engine, there is still a short.It will drain baterry overnight. This is the 2nd baterry in a month. Could it be engine fuse panel? I havent ever had a starter short out is that a possabilty?? i
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[pos battery post] ----- [load] ---- [neg battery post]
I suppose you call the wire between [load] and [neg battery post] negative wire. If you see 12 V on this wire, it is open. Am I missing something?
If I wanted to find a circuit that drains battery, I would connect a current meter and start removing fuse one by one, until current drops to near zero.
[pos battery post] ---- [current meter] -----
I suppose you call the wire between [load] and [neg battery post] negative wire. If you see 12 V on this wire, it is open. Am I missing something?
If I wanted to find a circuit that drains battery, I would connect a current meter and start removing fuse one by one, until current drops to near zero.
[pos battery post] ---- [current meter] -----
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You might just try disconnecting the harness to the alternator first. There may be bad diodes (s) that are allowing the current to run backwards in that circuit. If that's the case the voltage is possibly going to ground, and that would surely drain the battery.
I've also had cabin lights not shut off and do the same thing.
Paker has the right approach if the above doesn't show anything. There aren't that many circuits that are hot all the time.
Dave
I've also had cabin lights not shut off and do the same thing.
Paker has the right approach if the above doesn't show anything. There aren't that many circuits that are hot all the time.
Dave
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Catfish
Sorry I see you already tried the alternator. The problem may be in the supply lines to either fuse block then, because regardless of how many fuses you've pulled, the short is still there, so it seems like it must be shorted before either distribution block.
Dave
Sorry I see you already tried the alternator. The problem may be in the supply lines to either fuse block then, because regardless of how many fuses you've pulled, the short is still there, so it seems like it must be shorted before either distribution block.
Dave
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Uh, okay. Now I see. So the short is even before the fuses/relays (since you pulled all relays and fuses already).
Since the battery drains overnight, it is not a dead short, but 1-amp-short. You know what I mean. Have you considered an IR thermometer? I bet it can detect temp difference between 1-amp-short and the rest of wiring. It has a decent spatial resolution. The ones I use at work do.
Since the battery drains overnight, it is not a dead short, but 1-amp-short. You know what I mean. Have you considered an IR thermometer? I bet it can detect temp difference between 1-amp-short and the rest of wiring. It has a decent spatial resolution. The ones I use at work do.
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