I recently bought a 96 HDJ81 with a 1HD-FT and enjoyed a few week long honeymoon daily driving it until one morning it wouldn’t start. Fast forward two weeks and I’m now intimately familiar with the 24 volt starter system and testing procedures although it appears the real problem is my alternator which is only putting out 12.5V at 1600rpm after the engine has been running at idle for 10-15 minutes. I’m planning on removing the alternator and getting it tested today but I’ve already been thinking about upgrading it to a higher output alternator if my current one is bad. There are a lot of upgrades out there running from 110A all the way up to 390A. I think any of these would require upgraded wiring to the batteries but my question is since the hot from the alternator goes to the 12/24V switching solenoid can the solenoid itself handle the higher amps from an upgraded alternator? Is anyone running upgraded alternators with the 24V starter and if so what modifications did you make to accommodate the extra amps? I definitely don’t want to fry that expensive solenoid.
1HD-FT Alternator Upgrade with 24 Starter (1 Viewer)
- Thread starter OkiThe80
- Start date
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The starter pulls more than the alternator puts out. You need to upgrade the cables from alternator to battery and the main ground cable isn’t a bad idea either but don’t need to mess with anything else.
I don't think the 24 volt start solenoid plays any part in charging?
The two batteries are connected in parallel until you turn the key to start (solenoid unpowered), then the solenoid is powered to switch the batteries to a series connection.
The two batteries are connected in parallel until you turn the key to start (solenoid unpowered), then the solenoid is powered to switch the batteries to a series connection.
- Thread starter
- #4
Maybe I’m overthinking it. The alternator output goes directly to the main battery positive terminal. For the second battery, the positive terminal connects to the 2+ terminal on the solenoid. The main battery positive terminal connects to the 1+ terminal on the solenoid. In order for the second battery to charge the current would have to flow through the 1+ solenoid terminal out the 2+ solenoid terminal and back to the second battery’s positive terminal I think. That got me wondering if the solenoid could handle the extra juice if I upgraded the alternator. I could be misunderstanding the wiring though.
I don't have the wiring diagram to look at right now, so going from memory.
But the 24volt change over relay will have a "normal" state where it is not energised.
Current will pass through to charge the second battery without requiring the solenoid/ relay to do anything
My memory, is the second battery only has large cables running to it? No small cable?
But the 24volt change over relay will have a "normal" state where it is not energised.
Current will pass through to charge the second battery without requiring the solenoid/ relay to do anything
My memory, is the second battery only has large cables running to it? No small cable?
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- #6
Yeah the second battery has some pretty beefy wires to both the positive and negative terminals. I think I’m gonna go with a pretty mild upgrade to 120 amps so I don’t think I’m gonna have to beef up the wiring much other than the cable from the alternator itself but I’ll check the gauge of the other wires to make sure. Thanks for the help!
correct
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- #8
I ended up going with the alternator that Cruiser Brothers sells. It is the Terrain Tamer unit and it’s listed on their website as 120 amps but the box it comes in says 110 amps. Service was good and I got it quickly which is what I needed at the time. The alternator didn’t quite line up perfectly with the upper adjustable mounting bracket. I ended up having to slot one of the holes in the upper mounting bracket where it attaches to the front of the engine in order to get some more play and line everything up. After that it bolted up fine.
I was in a hurry to replace the alternator for a trip but I was originally hoping for a higher amp unit. I contacted M2K about the pricing for some of their high output alternators but they didn’t respond quick enough to meet my timeframe. I figured I’d post the quotes they gave me at the time in case anyone else is looking since they don’t list prices on their website.
I was in a hurry to replace the alternator for a trip but I was originally hoping for a higher amp unit. I contacted M2K about the pricing for some of their high output alternators but they didn’t respond quick enough to meet my timeframe. I figured I’d post the quotes they gave me at the time in case anyone else is looking since they don’t list prices on their website.
