Yet another alternator question

[dsanderlmtv]

[mention]Ronmar [/mention] I believe I have a question that just might stump you but I would be surprised. I have a ‘98 M1078 with ECO hubs. I was driving it down the highway in seventh gear going 73MPH. The alternator in 7th gear was only given 26.2 V on the 24V gauge and on the 12V gauge I was getting 13.4V here’s the thing that stumped me. I started to climb a pretty good grade, the transmission which is a WTEC3 downshifted to the next gear and the alternator started to go up to 28V on the 24V side and, it was above 15V climbing to 16 V on the 12 V side. Once I got to the top of the hill, the transmission shifted in the seventh gear the volts on the 24V side went back down to 26.2V and the 12V gauge showed 13.4V again.
What do you think is causing the alternator to jump when shifting gears to a higher RPM, I’ve never seen that before. I’m in the process of changing all the wiring from the battery to the alternator to the starter into the cab, but I have not done this yet, I’m still curious to know why the voltage was climbing at a higher RPM.


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[Suprman]

The alternator was spinning faster at higher engine rpms

 

[Ronmar]

well being stumped is how you learn things… in this case, having been stumped by alternators a time or three, I may have an answer for you.

Alternators don't make full output until they reach full RPM. I will have to look at the pully sizes again, but at lower engine RPM you are probably below peak alt RPM. Now add in an overload condition(empty batteries sucking up all the alt output?) and the alt is driving to max field but is unable to deliver enough output to maintain rated voltage, until you up the rpm.

in my experience when an alt wont make rated output voltage, either it is overloaded(bad batts, bad wiring, or some heavy load applied), or it has a normal load and cannot support that load(bad alt or reg)…

these dual volts throw in some other curves. They must see the proper 12v out of the middle of a 24v series wired battery, otherwise they do not regulate properly. I have seen mine derate to lower output when not connected well…

 

[dsanderlmtv]

well being stumped is how you learn things… in this case, having been stumped by alternators a time or three, I may have an answer for you.

Alternators don't make full output until they reach full RPM. I will have to look at the pully sizes again, but at lower engine RPM you are probably below peak alt RPM. Now add in an overload condition(empty batteries sucking up all the alt output?) and the alt is driving to max field but is unable to deliver enough output to maintain rated voltage, until you up the rpm.

in my experience when an alt wont make rated output voltage, either it is overloaded(bad batts, bad wiring, or some heavy load applied), or it has a normal load and cannot support that load(bad alt or reg)…

these dual volts throw in some other curves. They must see the proper 12v out of the middle of a 24v series wired battery, otherwise they do not regulate properly. I have seen mine derate to lower output when not connected well…

I had a feeling you couldn’t be stumped lol. I’m excited to tell you that I’m finally going do the conversion that you have on your YouTube video stay tuned.


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[dsanderlmtv]

Wire integrity issue, I removed the kick panel to start the install of the Victron 24v to 12v converter under the fuse panel and here is what I found. Everything is working as it should but how can I repair them without replacing the wire assembly. I was thinking to use “liquid electrical tape.” Has anyone had this issue and how did you handle it?

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[GeneralDisorder]

Yikes. That's horrible. Ideally you should replace the entire harness. If all the wiring in the dash looks like that - there's not really any good options besides finding a donor truck with a better condition harness. That level of insulation deterioration speaks to a very harsh environment or possibly a batch of incorrectly manufactured wire.... Hell my truck came from El-Paso and did a tour in Kuwait and my wiring doesn't look like that. I would say that's compromised so fundamentally that the best course would be to inspect and replace every stitch of failed wiring in the truck if you want any piece of mind that it's not going to leave you walking at some point.

 

[dsanderlmtv]

Yikes. That's horrible. Ideally you should replace the entire harness. If all the wiring in the dash looks like that - there's not really any good options besides finding a donor truck with a better condition harness. That level of insulation deterioration speaks to a very harsh environment. Hell my truck came from El-Paso and did a tour in Kuwait and my wiring doesn't look like that. I would say that's compromised so fundamentally that the best course would be to inspect and replace every stitch of failed wiring in the truck if you want any piece of mind that it's not going to leave you walking at some point.

I live in El Paso and my truck came from Fort Bliss. I have checked behind the dash and the only spot that the wires are doing this is right at the connection point to the grey block not sure what to call that thing. I hate that I found it because what I didn’t know didn’t hurt but now I do.
Guess my next question is who or where could I look for a replacement harness?


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[Mullaney]

Wire integrity issue, I removed the kick panel to start the install of the Victron 24v to 12v converter under the fuse panel and here is what I found. Everything is working as it should but how can I repair them without replacing the wire assembly. I was thinking to use “liquid electrical tape.” Has anyone had this issue and how did you handle it?

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.
Like @GeneralDisorder said... You need to start replacing the wires. Even if you decide to use "liquid electrical tape" on the outside of the bundle - all you need is a big bump - and some piece of wire falls out from between another wire, and poof. Up in Smoke!

 

[GeneralDisorder]

That's the WTEC III transmission control module.

Start calling and messaging the surplus truck and parts guys on here and on the wider internet. Someone has a parts truck with a harness. The biggest problem isn't going to be finding a harness it's going to be finding the exact same harness used on your truck. S&S made running changes almost monthly on these trucks during manufacture. Just in the A1 trucks there's like 25 serial number ranges with distinct differences - possibly not all of them involving wiring but when you get into the electronic TM's they divide the manual into these serial number ranges for both parts and procedures.

If the damage is limited to just a section of harness you might be able to make that portion or find a donor truck where you can harvest just that section. Personally I would be looking for an entire donor harness or maybe even buy a whole cab if you can find it and just swap the whole thing.

The biggest hurdles will be finding the exact same harness, and the labor to R&R it on the donor and your truck.

I did find this with a quick google search. Looks like a chore and time consuming but I don't see any options that don't involve hours if not days of labor.

Harness Repair Kit - Allison WTEC3 TCM - Blue Connector

A harness repair kit for an Allison Transmission Control Module (TCM) with WTEC III transmission electronics. This kit is intended to replace the 32 Pin BLUE Male plug for the TCM connection port.

kustomtruckparts.com

 

[dsanderlmtv]

That's the WTEC III transmission control module.

Start calling and messaging the surplus truck and parts guys on here and on the wider internet. Someone has a parts truck with a harness. The biggest problem isn't going to be finding a harness it's going to be finding the exact same harness used on your truck. S&S made running changes almost monthly on these trucks during manufacture. Just in the A1 trucks there's like 25 serial number ranges with distinct differences - possibly not all of them involving wiring but when you get into the electronic TM's they divide the manual into these serial number ranges for both parts and procedures.

If the damage is limited to just a section of harness you might be able to make that portion or find a donor truck where you can harvest just that section. Personally I would be looking for an entire donor harness or maybe even buy a whole cab if you can find it and just swap the whole thing.

Oh man…I have a Frankenstein truck from the military because when I got the truck from Gov Planet, I found that the transmission had a date stamp of 2012 and the truck is a ‘98. There is signs the truck was once picked up with a forklift and both driver-shafts along with the transmission and transfer case is newer.


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[dsanderlmtv]

That's the WTEC III transmission control module.

I did find this with a quick google search. Looks like a chore and time consuming but I don't see any options that don't involve hours if not days of labor.

Harness Repair Kit - Allison WTEC3 TCM - Blue Connector

A harness repair kit for an Allison Transmission Control Module (TCM) with WTEC III transmission electronics. This kit is intended to replace the 32 Pin BLUE Male plug for the TCM connection port.

kustomtruckparts.com

Thanks for the link, it’ll be tough but I feel like I can buy the connector and splice to the existing harness.

Like I said, the rest of the wiring on the truck is in great shape just that last section maybe only four or 5 inches of the harness is cracked like that everything else on the truck is in perfect shape.


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[GeneralDisorder]

Well that's good that you have a newer transmission and driveshafts! I would be happy about that. These transmision suffered from a C6 thrust bearing/bushing issue in the transfer case that is a can of worms if you are afflicted by it. I really like the ECO hubs for keeping these transmissions at much lower shaft speeds and cooler fluid temps. It certainly can't hurt the odds of avoiding that pitfall.

And yeah - if it's just that section - buy the replacement I linked to or a similar one (check pricing - that was the first link I clicked on).

 

[Suprman]

The blue is harness to cab bulkhead. I have them new. You need to check your cab to trans harness see if it looks the same

 

[dsanderlmtv]

The blue is harness to cab bulkhead. I have them new. You need to check your cab to trans harness see if it looks the same

I’m working on the truck is as we speak. I’ll keep you posted and yes maybe you can help me out.


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[Ronmar]

Yea its usually the cab down to trans harness where the insulation transforms to crayola crayon... inside the cab seems a little unusual...

 

[dsanderlmtv]

Yea its usually the cab down to trans harness where the insulation transforms to crayola crayon... inside the cab seems a little unusual...

Since I have you tuning in right now, can you help me out and tell me what this device is next to the polarity protection device that I’m pointing to? Is it important or can I delete it?

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[dsanderlmtv]

Keeping my fingers crossed I hope this is the reason why I’ve been having alternator issues. This is the 12 V positive from battery to the PPD. Looks like somewhere in the past it might’ve been cut on accident, possibly by somebody changing a battery. It was behind the batteries in the battery box.

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[Ronmar]

The item you are pointing to in the first picture is called an instrument shunt. It is a high current precision resistor. By reading the voltage developed across the resistor/shunt at the small terminals with a dc voltmeter(millivolt meter), you can accurately measure the current being pulled thru it. .001V = 1Amp. .100V = 100A ect. The large cables attached to it run to the battery -/gnd connection and the starter motor casing connection. The small wires run to the Standard Test Equipment cannon plug connection under the drivers dash.

Only used by the STE system, serves no practical purpose, can be replaced by a single cable from batt gnd to starter case connection on the forward end of the starter motor, thus removing 2 of the out in the weather connections… in the case of the A0 STE system, the money would have been better spent on manuals and drawings… you can pull that cannon plug, black plastic boxe and “freq divided” module under the dash. Takes 5 minutes ahd disconnecting two connectors inside the dash…

 

[dsanderlmtv]

The item you are pointing to in the first picture is called an instrument shunt. It is a high current precision resistor. By reading the voltage developed across the resistor/shunt at the small terminals with a dc voltmeter(millivolt meter), you can accurately measure the current being pulled thru it. .001V = 1Amp. .100V = 100A ect. The large cables attached to it run to the battery -/gnd connection and the starter motor casing connection. The small wires run to the Standard Test Equipment cannon plug connection under the drivers dash.

Only used by the STE system, serves no practical purpose, can be replaced by a single cable from batt gnd to starter case connection on the forward end of the starter motor, thus removing 2 of the out in the weather connections… in the case of the A0 STE system, the money would have been better spent on manuals and drawings… you can pull that cannon plug, black plastic boxe and “freq divided” module under the dash. Takes 5 minutes ahd disconnecting two connectors inside the dash…

Have I thanked you yet for all your help? If not, thank you in advance. You are one very smart man. People like you on this site that gives me the encouragement to do this on my own. It seems very daunting but with help from someone like you it’s easy.


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[coachgeo]

The item you are pointing to in the first picture is called an instrument shunt. ...

hmmm.... value of STE.. is that "not a value" cause folk just are not capitalizing on it? like can you pull an amp signal of STE?

Anyway.. that'ss a whole new topic best for another thread .... especially since I'm not sure what the heck STE even is.... (think its about some archaic electrical test port under A0 dash)