LMTV Abs troubleshooting

[aw113sgte]

Well checked under the PDP and found a lot of power distribution stud nuts finger tight. Also some corrosion to clean off. Found paint under the chassis ground stud as well. Fixed everything but still same situation with ABS. The "ignition voltage" is still reading under the "battery voltage" (I've seen it anywhere from matching to about 2V low) and the "ABS brake" still shows "N/A" which is different than others I've seen.
Still more work to do cleaning up in the switch box next to the battery and pull out the LBCD and clean it up.
Haven't probed voltage at the ABS computer under load yet either.
Update: checked voltages at pins 1, 2 between gnd pins 11,12 and also chassis gnd. They were all less than .1v difference from what wabco software reported as "ignition voltage". I can only assume it's getting battery voltage reading from the bus?
Still have some more voltage I can check but am loosing faith in finding the issue. Almost seems like a config issue with the ABS computer....your abs light is on and you say no abs is available but don't give me any error codes and all wheels read fine and modulators are all good too ...wtf

 

[aw113sgte]

Checked some voltages:
Battery voltage: 12.48-12.51 for all 4
Ignition on voltage - at batteries: 12.33V
Cranking voltage min - at batteries: 10.13V

At terminal under PDP and at ABS ecm between both +12v and both ground wires mirrored the voltages at PDP
Ignition on: 11.34V
Cranking voltage min: 8.55V

So basically a 1V drop though the LBCD and associated wiring with ignition on and about 1.6V when cranking. That 8.55V is also below what ABS ecu states as required - 9.0V

 

[GeneralDisorder]

LBCD voltage drop should be about 0.5v or so. 1.0v is a lot. 1.6v is unacceptable.

12.6v is fully charged for a flooded lead acid battery so you are close there.

 

[aw113sgte]

Soo....is this normal or a really odd repair?

 

[GeneralDisorder]

Soo....is this normal or a really odd repair?

That is normal. It's a fusible link.

 

[aw113sgte]

Well that's a strange stepped stud, hard to tell but looks like there might be a bevel washer where that nut came out. Looks like the nut had to be epoxied while the stud was installed as well.

 

[GeneralDisorder]

That whole unit is trash IMO.

LBCD replacement due to loose studs. CARNAGE!!

When addressing loose and corroded connections at the LBCD I noted that several studs were loose in the housing. After confirming with several members that this was a clear indication of failure (the unit is no longer sealed against moisture at the very least), I procured and installed a...

www.steelsoldiers.com

 

[aw113sgte]

That whole unit is trash IMO.

LBCD replacement due to loose studs. CARNAGE!!

When addressing loose and corroded connections at the LBCD I noted that several studs were loose in the housing. After confirming with several members that this was a clear indication of failure (the unit is no longer sealed against moisture at the very least), I procured and installed a...

www.steelsoldiers.com

Yeah I saw that. The back has no discoloration and the internal threads look good. I'm sure I could spend the time to fix it up but juice worth the squeeze for old caps... probably not. I see a whole load of them for sale from a vendor on eBay, although they don't look as nice condition as the one you got. You have any other source for them or recommendations?

 

[GeneralDisorder]

The one I got one in that thread is from this guy and cleaned up really well:

C.E. Niehoff and Co. Load Battery Control Device 76761-N2003 19207SOCN12422851 | eBay

C.E. Niehoff and Co.

www.ebay.com

There's vendors here on the SS forum that have them to. You could check with @Suprman and @wheelspinner.

 

[GeneralDisorder]

Also - for the time being and for testing while you wait for a replacement - don't hesitate to connect the batt and load cables for the 12v and 24v respectively together with some bolts and nuts (and insulate them). As long as your batteries are charged and you don't connect them backwards the LBCD really serves no purpose.

 

[aw113sgte]

Also - for the time being and for testing while you wait for a replacement - don't hesitate to connect the batt and load cables for the 12v and 24v respectively together with some bolts and nuts (and insulate them). As long as your batteries are charged and you don't connect them backwards the LBCD really serves no purpose.
[/QUO

Also - for the time being and for testing while you wait for a replacement - don't hesitate to connect the batt and load cables for the 12v and 24v respectively together with some bolts and nuts (and insulate them). As long as your batteries are charged and you don't connect them backwards the LBCD really serves no purpose.

Awesome, that's the place I found.
I have the 100amp alternator and it will not run (orange flashing) while the intake heater is on. Boy does that thing draw some power. May be over the safe limit for mine, your 260 would likely fair far better with no lbcd

 

[GeneralDisorder]

Awesome, that's the place I found.
I have the 100amp alternator and it will not run (orange flashing) while the intake heater is on. Boy does that thing draw some power. May be over the safe limit for mine, your 260 would likely fair far better with no lbcd

Yeah I've never had mine disconnect. But I've not seen the 100A unit disconnect or fail to run with the grid heater running either - the grid heater is on the 24v side and that's the less loaded side of the alt (compared to the 12v with all the lighting turned on). I think you have some serious voltage drop across that LBCD and changing it out may solve that problem.

 

[aw113sgte]

Yeah I've never had mine disconnect. But I've not seen the 100A unit disconnect or fail to run with the grid heater running either - the grid heater is on the 24v side and that's the less loaded side of the alt (compared to the 12v with all the lighting turned on). I think you have some serious voltage drop across that LBCD and changing it out may solve that problem.

Good to know! Will try out the new lbcd and see if that changes things. It's also got 4x generic group 24(?) batteries currently so I'm not sure their performance

 

[GeneralDisorder]

Good to know! Will try out the new lbcd and see if that changes things. It's also got 4x generic group 24(?) batteries currently so I'm not sure their performance

Well many people have swapped to just two batteries and had no issues so four group 24's should be fine.

 

[aw113sgte]

Got a new LBCD because mine was crusty. New batteries as well. Showing .7 V drop across LBCD and voltage over 10v cranking. ABS still not functioning. All wheel sensors are reading properly, all modulator valves have good resistance to abs ECU. Not getting any error codes at all. ABS light is on and ECU shows abs as "N/A" almost like it's not programmed to have abs in use or something.
Mine:

Generaldisorder:
Note how his says "off" for abs instead of n/a. Also mine says I have 3276V on vehicle battery... Any ideas?

 

[aw113sgte]

Ordered a used ABS module off ebay. Looked a heck of a lot better than mine did...on the outside. I plugged it in but couldn't talk to it at all. Decided to pull it apart and see what I could find...well it's pretty obvious why it wasn't working:




Then I decided to pull my original one apart and it actually looked pretty good but there are small signs of water ingress on the board. Very unimpressed for a frame mount ECU these things only rely on seals and the board isn't potted. Found another used one to order and try out with a "inspected good" sticker from wabco in 2018. Fingers crossed.

 

[Suprman]

I have one here I think

 

[aw113sgte]

I have one here I think

Do you know if it's a known good one?

 

[Suprman]

Came off a fmtv based caiman mrap that was being scrapped. I have a few of them

 

[aw113sgte]

Came off a fmtv based caiman mrap that was being scrapped. I have a few of them

Sounds good I'll contact you if this next one is also bad. It's already shipped.