73 j2000, high resistance in charging circuit

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mjdriver
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Joined: Fri Oct 05, 2018 10:51 am

73 j2000, high resistance in charging circuit

Post by mjdriver »

My old alternator was dying, replaced alternator with regulator. Im getting around 13.5 to 14 volts at alt output lug, only getting around 12.5 at battery with loads off. Im thinking i should be to run a cable straight from the alt to the battery, or battery lug of solenoid. I like this idea better than bypassing the amp meter behind the dash. Just want to run it by the experts first.

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tgreese
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Re: 73 j2000, high resistance in charging circuit

Post by tgreese »

Here's what I suggested for the later models -

Image

This is what I did for my '82, which has a Delco alternator, but it should be essentially the same for the Motorola wiring. I expect a '73 does not have the bulkhead connector like the later Jeeps, but the charge wire still goes through the firewall and back to the battery as in later models. When you bypass the ammeter, that has the advantage of leaving the feed to the dash and lights intact. You can't just disconnect the entire ammeter feed circuit, since you need that wire that goes to the dash and lights.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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mjdriver
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Re: 73 j2000, high resistance in charging circuit

Post by mjdriver »

tgreese wrote:Here's what I suggested for the later models -

Image

This is what I did for my '82, which has a Delco alternator, but it should be essentially the same for the Motorola wiring. I expect a '73 does not have the bulkhead connector like the later Jeeps, but the charge wire still goes through the firewall and back to the battery as in later models. When you bypass the ammeter, that has the advantage of leaving the feed to the dash and lights intact. You can't just disconnect the entire ammeter feed circuit, since you need that wire that goes to the dash and lights.
Ok, im not that familiar with ammeters, so if i just disconnect the feed from the alt to the meter, the current wont flow back through the meter to the lights, or is it just not a good idea to have it like that? So your basically saying i should take the meter out of the picture, than i can just run a cable from the alt to thr batt.

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tgreese
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Re: 73 j2000, high resistance in charging circuit

Post by tgreese »

Connect the alternator directly to the battery. I suggest you add a fusible link in the alternator wire, to protect the Jeep from fire.

You need a voltage/current feed to the dash and lights, regardless of the ammeter. If you just disconnect the ammeter feed, you may also disconnect the dash and lights.

Look at the diagram. The "before" diagram (above) shows a loop through the ammeter. Disconnect one end of that loop and keep the connection to the dahs and lights.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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mjdriver
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Joined: Fri Oct 05, 2018 10:51 am

Re: 73 j2000, high resistance in charging circuit

Post by mjdriver »

Ok so when i bypassed the meter, the red lead was loose, not really loose but enough to were it moved some if i put pressure on it. Im now getting around 13.8 no loads at battery with a wire straight to the alt, i cut the end off and heat shrunk the old amp meter lead. What size fusible link or fuse would you recommend? I think its a 35A alt.

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PossumJr
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Location: Eastern NC

Re: 73 j2000, high resistance in charging circuit

Post by PossumJr »

General rule of thumb for fusible links is to use 4 sizes (gauge) smaller than the wire on the circuit your are protecting, as the fusing current of that size wire will be roughly half of the larger one. 14 awg would use 18 awg fusible link, 12 awg use 16 awg, etc. If you stick with factory wiring, which should be 10 awg on the main leg to the ammeter, use a 14 awg fusible link.
1979 J10, 360/QT
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