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Yes there is an engine block to frame ground near the starter IIRC. The chassis to cab cable is behind the grill on the passenger side. The chassis side of the cable is unreachable.... you will see. I haven't had an issue with it yet but my plan is to simply add a second braided ground strap...

Prime example of why it is imperative to clean every connection. That is VERY LIKELY factory. I've run into a severe voltage drop between the cab and the chassis on a 2021 A1P2 due to excessive paint under the cab to chassis ground strap. You are starting to see the situation you are dealing with.

Right. The batteries are expected to pickup this intermittent load and then be recharged by the alternator. The alt will likely go to 100%+ operation (not 100A because engine is at idle immediately after start) for a bit till the AIH turns off. Shouldn't hurt it for the short time it's on and...

70 to 90 amps is normal for the 24v AIH. The 12v versions used on some applications can draw 200A.

On my 260A it was definitely a PWM drive. I scoped the signal and caught it going static (to battery voltage) and over-driving the 28v on my truck. But the 260A has the PWM on the positive side, while the 100A is driven from the negative side IIRC. Again I'm no EE but the 260A is newer and...

Tell me more about this high 14v reading during starting? Maybe a video of what you are reading....... AIH runs on 28v and on my truck I do see the 28v side drop when the AIH is in play. One of the first problems I fixed with my truck was that some PVT Snuffy type had connected the AIH to the...

Engine ECM uses 24v exclusively from my experience. Although it will happily run on anything down to about 10v. At 28v it draws about 1.2A with the engine running. Only computer I'm aware of that runs on 14v is the ABS unit.

The electronic manuals have them listed under "Engine Electrical System Schematic" - they have the internal transmission wiring harness schematic also.

The A1+ trucks don't have a bell-housing pickup. The ECM is generating the RPM internally using the top and bottom camshaft timing sensors. Your choices are to pin the ECM chassis connector to get the dedicated tach drive much like we do to gain access to the cruise control functions, or use the...

The A1+ trucks don't have any provision for a tach except the J1939. The dedicated tach output from the ECM is not pinned much like the cruise control is not pinned. Since these trucks have no hand throttle they have no need of a tach. The A1+ winch trucks don't have the tach they just have a...

Sure they do: 3126: C7:

I would just get a J1939 tach. Such as: https://www.vdo-instruments.com/product/singleviu-80mm-j1939-3000rpm-tachometer-retail-pack-with-harness/

Have you gone through the troubleshooting manual and done the tests on the alternator itself? Your ECM has a dedicated tach driver output so using the alternator VR is not necessary.

My primary meter is the Agilent (HP) U1252A which is what the military uses in the SWICE kits and I don't see fluctuations like that on normal DC voltage settings. Fluke may be faster I'm not sure - but I am using a $600 meter (the newest version being the 1252B which is $650)....... I would...

These alternators have a lot of ripple. Niehoff considers it normal and it's an effect of the slow brushless response. 15v-16v is too high. But the fluctuation is normal - really need an oscilloscope. DVOM is not a great tool for this job. Even an analog meter is better that that digital mess...

First off - stop buying anything from MME. $800 for a 100A regulator is robbery. Check out my thread on the topic of OVCO: https://www.steelsoldiers.com/threads/2008-a1r-with-260a-charging-questions.206182/ And the carnage inside the LBCD...

These trucks have issues with not keeping the 12v and 24v battery pairs evenly charged. It's best to rotate them front to back every few months. Best is to drive them regularly or at least keep the batteries on a maintainer. I would recommend a proper tester to keep an eye on them. This kind of...

The air inlet heater should be pulling it's power from the batteries. The alternator only needs to replenish the batteries. Have you tested the condition of your batteries? Disconnect each one and test it. Sounds to me like you have questionable batteries. or connections. Ground connections and...