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I am going to have ac put in 89MJ that never had ac. I am not doing it myself. I will use same mechanic that just replaced all ac in an 87MJ that did have it. I asked him if i will need to replace alternator with larger one and battery also. He said he would check ratings. Reasonable. I asked if voltage regulators were still separate back then. He did not recall but would check. Decades ago, regulators were replaced at time alternators were. A bad regulator could burn up a new alternator. My understanding is that at some point regulators were built into alternators. Today the function is done by on board computer. My questions: was regulator still separate on MJs or built in? Other than alternator and regulator, will any other changes be needed? I don't want to burn anything up which mechanic said could happen to undersized alternator.

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Hornbrod, i was thinking you were probably a nice guy up until now. That was  scary thread. It appears you knew what you were talking about 10 years ago.  I am not on fb (don't want to be) so could not see that last link.  Long story short, you think alternator with more output will require some rewirimg and fuse panel? You think the Renix era had separate voltage regulators?

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15 minutes ago, Manche757 said:

Long story short, you think alternator with more output will require some rewirimg and fuse panel? You think the Renix era had separate voltage regulators?

 

Whenever you increase the load on a vehicle's electrical system by adding devices like A/C, lighting, cooling fans, etc., the alternator and it's associated wiring should be upgraded based on the increased total load. Our MJ's electrical systems were barely adequate from the factory to begin with. Increasing the alt capacity requires a set of larger gauge mains cables at a minimum. There are kits available especially for our rigs; forum member Mean Lemons makes a quality kit that has been reviewed very favorably. When upgrading the mains cables I also think it's a good idea to install an ANLfuse in series with the alternator output. The ANL fuse should be sized for the estimated total vehicle load + 25% or so. The ANL fuse's job is to protect the alternator and it's associated wiring should a catastrophic short occur.

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I prefer Mega Fuse over ANL... the fuseholders are way more sturdier and made out of more stronger type of plastic. 

 

For some one strange reason, ANL fuse holders are so brittle and break easily. (Different type of plastic) I had to replace them often so I phased them out in favor for Mega Fuse. 

 

 

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And not just that, the factory cables weren’t that great either.  I had to replace so many renix cables because the insulation simply corroded itself off and the copper was now completely exposed. Due to years of exposure to oils and such.

 

so replacing the cables regardless of alternator upgrades or not. It’s still good idea to do it anyway 

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3 hours ago, Manche757 said:

Hornbrod, i was thinking you were probably a nice guy up until now. That was  scary thread. It appears you knew what you were talking about 10 years ago.  I am not on fb (don't want to be) so could not see that last link.  Long story short, you think alternator with more output will require some rewirimg and fuse panel? You think the Renix era had separate voltage regulators?

 

The Renix era MJs used Delco alternators with built-in voltage regulators. You can swap in a larger one with no rewiring needed, but increasing the wire size would be a wise precaution. Don't try to go too big, or you'll have problems fitting the alternator in the space available. The base alternator was a CS-121. The optional was a CS-130. Don't try to go larger than the CS-130 in physical size.

 

The CS-121 could be 61 or 74 amps. The CS-130 could be 85, 100, or 105 amp.

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So the 3 gurus are dealing with this.  So a Delco alternator does OR does not need a voltage regulator? I am seeing conflicting answers here and in earlier threads.   I am not looking for the cheapest way out of this.  I AM looking for a solution that will be the most trouble free AND the easiest for someone to figure out 10 years from now when it might need replacing and no ones remembers a nonstandard installation.  Not clear about which wires need up sizing. If a Delco does not need a voltage regulator and it was so dependable that thousands were made, wouldn't that option make the most sense?      

89MJ 4.0 going from no ac to factory style ac.  And a new twist: probably will go from manual windows to 97 doors with electrical windows; don't know if that matters

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46 minutes ago, Manche757 said:

So the 3 gurus are dealing with this.  So a Delco alternator does OR does not need a voltage regulator? I am seeing conflicting answers here and in earlier threads.   I am not looking for the cheapest way out of this.  I AM looking for a solution that will be the most trouble free AND the easiest for someone to figure out 10 years from now when it might need replacing and no ones remembers a nonstandard installation.  Not clear about which wires need up sizing. If a Delco does not need a voltage regulator and it was so dependable that thousands were made, wouldn't that option make the most sense?      

89MJ 4.0 going from no ac to factory style ac.  And a new twist: probably will go from manual windows to 97 doors with electrical windows; don't know if that matters

No, you do not need a voltage regulator. 

New 4g wires, including your charge wire.

Use a Megafuse, if you need a pic I'll get you one. 

 

If you want to know what works? Here-

jWTPQdF.jpg

 

Your mechanic will likely need to reclock, reason is shown here-

IOtHEa2.jpg

https://www.summitracing.com/parts/pwm-58137/applications/year/1988

 

Cheaper option for 105 amps is- 1986 Chevy Caprice, same as above but mounting holes are 1/2" further apart, you'll need to drill new hole in bracket and reclock as above. This alt will be rated at full rpm, not at idle as shown with the Powermaster. 

 

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4 hours ago, Manche757 said:

So a Delco alternator does OR does not need a voltage regulator? I am seeing conflicting answers here and in earlier threads.

...

89MJ 4.0 going from no ac to factory style ac.  And a new twist: probably will go from manual windows to 97 doors with electrical windows; don't know if that matters

 

The voltage regulator is built into the alternator. Not the ECU, the alternator itself.

 

Assuming your alternator is working, the first step is to see what you have. The numbers CS-121 and CS-130 refer to the case diameter in millimeters. 121 mm is 4-3/4 inches, 130 mm is 5-1/8 inches, so get out your tape measure. (Disconnect the negative cable from the battery before you go poking around the alternator with a steel tape.)

 

Looking at Autozone's alternators on-line, they say their new-manufacture Durolast Gold alternators may be 121 or 130 mm in size, but all are rated at 100 amps. That doesn't make sense to me. There's an independent shop near me that just rebuilds starters and alternators. I just had him rebuild an alternator for my '87 MJ. I wanted to be sure it was a 100-amp, or upgrade it to 100-amp if it wasn't. Initially, he said "No problem." Once he got into it, he found that it was a CS-121 rather than a CS-130, and that he couldn't find a 100-amp winding for the smaller size.

 

If your alternator is the CS-130, it's probably good for whatever you need, and you can wait until it fails before worrying about upgrading. If you have a CS-121, then you need to find out if it's the 61 or 74 amp version. I don't know how to do that in the vehicle without a specialized tester, so you might want to pull it and have it bench tested. The 74-amp version might be adequate for your increased needs -- the 61 amp might be marginal.

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8 hours ago, MeanLemons said:

I prefer Mega Fuse over ANL... the fuseholders are way more sturdier and made out of more stronger type of plastic. 

 

For some one strange reason, ANL fuse holders are so brittle and break easily. (Different type of plastic) I had to replace them often so I phased them out in favor for Mega Fuse.

 

Never had a problem with ANL fuse holders breaking, never heard of this problem either. Probably the old adage - you get what you pay for. The only advantage I'm aware of for the Mega Fuse I see is that it's normally a little cheaper.   :brows:

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6 hours ago, HOrnbrod said:

 

Never had a problem with ANL fuse holders breaking, never heard of this problem either. Probably the old adage - you get what you pay for. The only advantage I'm aware of for the Mega Fuse I see is that it's normally a little cheaper.   :brows:

Mega fuses are more expensive...ANL fuseholder and 2 fuses can be had for $8 shipped. 

 

A megafuse holder is approximately $7 and each fuse is $5

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14 hours ago, Eagle said:

 

The voltage regulator is built into the alternator. Not the ECU, the alternator itself.

 

Assuming your alternator is working, the first step is to see what you have. The numbers CS-121 and CS-130 refer to the case diameter in millimeters. 121 mm is 4-3/4 inches, 130 mm is 5-1/8 inches, so get out your tape measure. (Disconnect the negative cable from the battery before you go poking around the alternator with a steel tape.)

 

Looking at Autozone's alternators on-line, they say their new-manufacture Durolast Gold alternators may be 121 or 130 mm in size, but all are rated at 100 amps. That doesn't make sense to me. There's an independent shop near me that just rebuilds starters and alternators. I just had him rebuild an alternator for my '87 MJ. I wanted to be sure it was a 100-amp, or upgrade it to 100-amp if it wasn't. Initially, he said "No problem." Once he got into it, he found that it was a CS-121 rather than a CS-130, and that he couldn't find a 100-amp winding for the smaller size.

 

If your alternator is the CS-130, it's probably good for whatever you need, and you can wait until it fails before worrying about upgrading. If you have a CS-121, then you need to find out if it's the 61 or 74 amp version. I don't know how to do that in the vehicle without a specialized tester, so you might want to pull it and have it bench tested. The 74-amp version might be adequate for your increased needs -- the 61 amp might be marginal.

My best measurement indicates the 4.75" alernator. I looked for a plate but could not see any from above. Totally not visible from below. Put my phone down by back and below. I see no markings for part number or amps. I am surprised a 4.0 would have the smaller alternator. The deatails on driver door are totally blurred. I think it started life as a Pioneer but don't really know

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23 hours ago, HOrnbrod said:

 

Whenever you increase the load on a vehicle's electrical system by adding devices like A/C, lighting, cooling fans, etc., the alternator and it's associated wiring should be upgraded based on the increased total load. Our MJ's electrical systems were barely adequate from the factory to begin with. Increasing the alt capacity requires a set of larger gauge mains cables at a minimum. There are kits available especially for our rigs; forum member Mean Lemons makes a quality kit that has been reviewed very favorably. When upgrading the mains cables I also think it's a good idea to install an ANLfuse in series with the alternator output. The ANL fuse should be sized for the estimated total vehicle load + 25% or so. The ANL fuse's job is to protect the alternator and it's associated wiring should a catastrophic short occur.

Mean Leoms, tell us about your kit. Gotta link to it?

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30 minutes ago, Manche757 said:

Mean Leoms, tell us about your kit. Gotta link to it?

 

It's in the Forum Classifieds - Vendors section.

 

MeanLemons - I'm convinced regarding the ANL vs. Mega Fuse. Can you provide the distance between your Mega fuse holder mounting holes? If it'll work for me w/o drilling more holes, I'll buy one from you.

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20 hours ago, HOrnbrod said:

 

It's in the Forum Classifieds - Vendors section.

 

MeanLemons - I'm convinced regarding the ANL vs. Mega Fuse. Can you provide the distance between your Mega fuse holder mounting holes? If it'll work for me w/o drilling more holes, I'll buy one from you.

I ll get back to ya on that tonight 

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  • 2 weeks later...
On 8/12/2018 at 1:24 PM, HOrnbrod said:

 

It's in the Forum Classifieds - Vendors section.

 

MeanLemons - I'm convinced regarding the ANL vs. Mega Fuse. Can you provide the distance between your Mega fuse holder mounting holes? If it'll work for me w/o drilling more holes, I'll buy one from you.

I apologize for getting bit late on this 

 

the distance between two mounting holes are 4” apart. The mounting holes on the block is diagonally.  Not sure how your ANL are mounted in regard to orientation. 

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17 minutes ago, HOrnbrod said:

Unfortunately my ANL fuse holder mounting holes are inline so I'd have to drill at least another mounting hole. Thanks for checking though - appreciate it.   :L:

Depending on the orientation. You may only need to raise one end slightly.  Unless you are anal about keeping the holder level.  Lol 

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