Ammeter bypass

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Fire1
Posts: 51
Joined: Mon Sep 09, 2013 2:37 am

Ammeter bypass

Post by Fire1 »

I was advised in a previous question about upgrading my alternator that the ammeter bypass is a prudent mod. I search these pages and found some very good information in particular these links detailing the mod.

http://www.madelectrical.com/electrical ... ges2.shtml
http://www.drbob.tqhosting.com/tech/ammeter.htm

The drbob instruction best solution is to add an additional charging circuit and leave the original through firewall to dash/ammeter wires.
The madelectrical solution is the same with the addition of heavier duty wire through the firewall to the dash and bypassing the ammeter entirely.

The madelectrical solution is obviously very safe but is it necessary to change the wiring if the charging circuit has been isolated from the ammeter and the old wires never see high load. I'm ok with basic electrical and happy swinging a hammer but the dash wires terrify me.

Thanks to all those that replied to my previous post re the Powermaster alternator.
1980 J20 258 4 speed, stock suspension
1982 Cherokee NT 360 auto, stock suspension

1979bettywhite
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Joined: Tue Jul 25, 2017 8:14 am

Re: Ammeter bypass

Post by 1979bettywhite »

Fair disclosure, I am an amateur at most at wiring. Others on the board are more well versed on the subject. But unless you plan to run the Ammeter moving forward, then it seems like a wise decision to just do away with it's wiring while you are doing everything.

I run a separate voltmeter gauge and my Sniper EFI also provides me with a current voltage as well. I think these are just fine.

I just did my re-wire today based on this diagram:

http://www.ifsja.org/forums/vb/showthre ... 450&page=3

If Rick Serehill was ok with it, then it must be a worthwhile path to follow. Although, I am still running the stock alternator, so just used a 10ga charge wire with a 14ga fuseable link attached to it.

Also, I could not find a definitive answer on this one, but I went ahead and disconnected my red wire from the ammeter in the cab, snipped off the connector and wrapped it up well with electrical tape. My yellow wire I left disconnected in the engine bay and wrapped up with electrical tape as well. Plan to soon run another fuse panel in the cab and use this as my 12v source for it.

Gambler
Posts: 51
Joined: Wed Jul 06, 2011 4:28 am

Re: Ammeter bypass

Post by Gambler »

I just did this yesterday on my 75 j20. I also changed the setup at the coil like they talk about (adding a 10g charging wire from battery side of solenoid to alt). What you did in dash is fine.

Hud
Posts: 39
Joined: Sun Feb 24, 2019 12:30 am

Re: Ammeter bypass

Post by Hud »

In Mr. Bob's article he stated up to 85 modles, is this something Jeep corrected in later models, such as an 88? Do we still need to do this mod? thanks for the info!

weeegoneeer
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Re: Ammeter bypass

Post by weeegoneeer »

When the dash was redesigned for '86 and up they got rid of the ammeter, replaced it with a voltmeter, and got rid of the fire hazard. So, nope!
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Stuka
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Re: Ammeter bypass

Post by Stuka »

Honestly, I did the bare minimum, which was to move one wire over to the post that has the other wire on the back of the ammeter. Is this the ideal solution, no. But it took all of five minutes, I did it 15ish years ago, and thus far has worked fine.

If you are going and changing wiring anyway, or you just really want it done right, get the main feed out of the cab entirely. If you don't want to go quite that far, the secondary charging feed will get the majority of the current out of the cab.
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DARREN LILLY
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Re: Ammeter bypass

Post by DARREN LILLY »

I am waiting on a new 150 amp alternator to arrive & also want to order a set of daytona? digital guages, I dont have a bypass done yet so I want to leave the wiring alone untill ready for the new cluster installation as I read some methods involve cutting wires. Will installing these guages sort all the problems that require the bypass.
1979 chief 360 auto QT Australia

will e
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Re: Ammeter bypass

Post by will e »

DARREN LILLY wrote: Mon Jan 20, 2020 2:26 am I am waiting on a new 150 amp alternator to arrive & also want to order a set of daytona? digital guages, I dont have a bypass done yet so I want to leave the wiring alone untill ready for the new cluster installation as I read some methods involve cutting wires. Will installing these guages sort all the problems that require the bypass.
The short answer is no. Your new gauges probably will include a volt meter instead of an amp meter so you don't have to worry about overloading/burning up the amp gauge. You will need to come up with 'new' wiring for the volt meter.

The simple solution would be to take the two wires from the old AMP meter and spice them together. However, these are not a large enough gauge to handle 150amps that your new alternator can put out. You need to look at having direct wiring from the alternator to the battery.

You might be tempted to connect the old amp wires for the volts gauge but these are always live and it might drain the battery over time.
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DARREN LILLY
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Re: Ammeter bypass

Post by DARREN LILLY »

I looked at the madelectrical sites write up on the bypass & am thinking about going this way but will need to do wire changes for the alternator as it is a single wire type instead of the original set up. Do you think the old amp wires would be OK if the charging is direct wired from the alt to the battery with the 150 amp alt. Dakota guages were what I was looking at getting, anyone got an opinion these. Thanks
1979 chief 360 auto QT Australia
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tgreese
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Re: Ammeter bypass

Post by tgreese »

The original wires are ok, but you cannot keep the ammeter without looping the whole charging current to the dash. That's how the ammeter works: it looks at the charging current going through it.

Connecting the charge wire directly to the battery from the alternator is a good idea. I recommend adding a fusible link between the alternator and the battery, to protect the Jeep from a catastrophic short in that circuit.

To me, there is no advantage to the single wire alternators.

There is a sticky thread on the IFSJA forum with links to threads about this topic. http://www.ifsja.org/forums/vb/showthread.php?t=184890 JMO - this topic is not that complicated, but you might not know that from the amount of advice and number of opinions that have been offered. Don't get overwhelmed.

Here's what I did:

Image

Above is before, and below is after. The 14g wire in yellow is the original fusible link. The splice labels B & K are correct for my '82.
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fsj454
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Re: Ammeter bypass

Post by fsj454 »

Tgreese nice job . My 82 is set up like that with a 120 amp and stock wires duel battery and isolator woks good
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