My '74 Cherokee recently acquired an electrical issue in the headlights circuit. I have replaced the headlight switch as I thought it was the issue to no avail. The headlights and side markers are dimly flashing when the headlight switch is pulled. When the headlights are turned on the ammeter is bouncing all over the place too. All the other lights (brake and turn signals) still work. I unplugged the dimmer switch on the floor and the ammeter still goes wild when the headlight switch is engaged. Any idea where to start looking to troubleshoot this issue? There is no visible corrosion on any of the grounds and I have started to clean them up as precaution but nothing seems to be fixing this issue.
Headlights dead, ammeter on the frits
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time to bypass the ammeter, disconnect battery, and reaching behind the dash -if you can- connect both ammeter wires to the same post for a quick test. Various mods are possible
check this
Michel
74 wag, 349Kmiles on original ticker/trany, except for the rust. Will it make it to the next get together without a rebuilt? Status: needs a new body.
85 Gwag, 229 Kmiles. $250 FSJ test lab since 02, that refuses to give up but still leaks.
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Nailed the issue
I found the ground wire from the ammeter to the dash ground was burnt out. It looked like the original approx. 16awg was melted and then the dash was grounding through the headlight circuit. The burnt out headlight switch was the symptom not the cause! I have replaced it with a 12awg fresh wire and soldered on the pin connector for the gauge clip. It was an easy fix once I found the culprit.
I did however break my bezel on the gauge cluster, I was lazy and instead of taking off dropping the column I forced it too much. Not too happy about that one but oh well.
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Glad you found the real cause and fixed it.
Be aware that neither wire on an ammeter is a ground. Both are always hot. One side connects to the battery, and the other to distribution point and then onto the alternator.
With the engine off, all power comes through the ammeter to the distribution.
With the engine running, power comes from the alternator (as long as its output voltage is higher than the battery's). If the battery is low, the ammeter will show charging.'85 Grand Wagoneer
360 727auto, NP229
body by beer (PO)
carries wood inside
no "wood" outside
My other car is a fish
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Originally posted by nograinGlad you found the real cause and fixed it.
Be aware that neither wire on an ammeter is a ground. Both are always hot. One side connects to the battery, and the other to distribution point and then onto the alternator.
With the engine off, all power comes through the ammeter to the distribution.
With the engine running, power comes from the alternator (as long as its output voltage is higher than the battery's). If the battery is low, the ammeter will show charging.
Best solution IMO - Keep the distribution point, remove the ammeter, and run the alternator charge wire directly to the battery. Install a voltmeter.Last edited by tgreese; 12-04-2017, 12:12 PM.Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk
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I beg to differ on part of that. Once the battery is charged, no power should be flowing through the ammeter. It's got the potential (14.5 Volts), but no flow (0 amps) since there is no demand.
When additional equipment is added to the battery post, its another story.'85 Grand Wagoneer
360 727auto, NP229
body by beer (PO)
carries wood inside
no "wood" outside
My other car is a fish
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Originally posted by nograinI beg to differ on part of that. Once the battery is charged, no power should be flowing through the ammeter. It's got the potential (14.5 Volts), but no flow (0 amps) since there is no demand.
When additional equipment is added to the battery post, its another story.
Once the demand from starting is made up, the battery should not discharge again until there is more demand on the alternator than the engine speed can support. That's a fairly uncommon situation, ie when you are running a winch or welder, or when there is something wrong with the alternator or regulator.Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk
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Originally posted by DattMtnI found the ground wire from the ammeter to the dash ground was burnt out. It looked like the original approx. 16awg was melted and then the dash was grounding through the headlight circuit. The burnt out headlight switch was the symptom not the cause! I have replaced it with a 12awg fresh wire and soldered on the pin connector for the gauge clip. It was an easy fix once I found the culprit.
I did however break my bezel on the gauge cluster, I was lazy and instead of taking off dropping the column I forced it too much. Not too happy about that one but oh well.Member, FSJ Prissy Restoration Association
1976 Cherokee 401 Quadratrac
4" Rusty's Spring lift 31" tires
All MSD ignition system
EZ EFI status: Running Smooth!
1999 Dakota Seats
2000Tahoe Console
Powertrax No-slip lunchbox rear locker
Amp meter delete
Two Wire 94Amp Alternator upgrade
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