Lighted indicator display illuminates in chase pattern

[Ortizjr1991]

M1088a1p2, no gauges work, truck turns on and is operational, lights inop, LED's on voltage regulator and LBCD aren't illuminated. Any ideas on what the problem could be?

 

[BKubu]

I think you have a battery/charging issue.

 

[coachgeo]

There is a lot of mentions in here of the wire that excites the alternator going fubar.... Thus no charge..... thus all the 12v does not work well..... followed soon by the 24v as batteries drain. Try searching in here under Suprman as member with keywords ... alternator wire charging ... might find it . You will need to use Advanced. search here or via your favorite search engine inside this website

 

[Suprman]

A1 trucks have other issues. Could be voltage regulator/alternator issue. Could be related to the polarity charging box under the spare tire. You can unplug the mil connector from the polarity box and see if symptoms change. See if there is 24v at the front terminal on the regulator marked 24v. You have to take the lead off temporarily, start the truck and then measure see if it has 24v at the lead. You can get a false reading trying to measure with the wire on the regulator terminal.

 

[Ortizjr1991]

I don't get any voltage on the regulator

 

[Suprman]

So you took the lead off the regulator 24v terminal and measured it and there is no voltage at the lead when the truck is running?

 

[Ortizjr1991]

Yes. Also, I get 24 on the alternator and LBCD, but I don't get 12 on either

 

[Suprman]

If you dont have 24 volts at the alternator 24v regulator excite terminal the alternator will just spin and not make any power. If something is connected wrong that could be the cause though. Go the the lbcd and measure the 12 volt in post and the 12 volt out post. If there is no 12v at the in post then maybe something at the batteries isnt connected correct.

 

[D92!]

I’m currently having this same issue. But I have 12v on the cable that comes from the DRIC to the 12v Batt. Post on the LBCD. When I connect the cable on the post it starts dumping volts when master is turned on. Goes from 12v down to three.

 

[Suprman]

Voltage drops on the lbcd in and out? Have you checked your batteries and their connection?

 

[Ronmar]

I’m currently having this same issue. But I have 12v on the cable that comes from the DRIC to the 12v Batt. Post on the LBCD. When I connect the cable on the post it starts dumping volts when master is turned on. Goes from 12v down to three.

Nothing like reviving an old thread I am not familliar with the acronym “DRIC” What/where is that?

Everything starts at the batteries. What are the voltages at all 4, both switched off and with ignition switch on? And when I say voltage, I am wanting to know the decimal. A charged battery that has set for more than a half hour or so to equalize should read around 12.6-12.8V Typically. If they don’t, charge them And get them load tested. A lead acid has a fairly small voltage range between fully charged and empty. 12.06V would be a 50% charge, 11.3V would be about 10% charged(these are unloaded and after setting to equalize).

After the batts are load tested, pick the best 2 to re-install(one inner near frame and one outer) and tape over the unused battery cable connections. The 4 batts are a terrible load for the alternator and have trouble fully charging unless you run the truck for long hours regularly. Low state of charge kills batteries and causes even worse alternator load issues. Cat specs a pair of 100AH group 31 batteries for the engines in the LMTV. The 4 battery bank is the root cause of many of the electrical issues on these vehicles…

Voltage is not considered good until it is measured under load. The symptom of 12v falling to 3v when you turn on a load is either a very bad connection or a badly sulfated battery(has chemically charged electrolyte but not enough plate surface to deliver any significant current). A bad/high resistance connection will pass full voltage thru the circuit, but since resistance resists current flow, as soon as you try and pull any current thru that connection the voltage on the downstream side will fall off drastically. If it has a LBCD it also has a manual disconnect switch and a pair of disconnect relays. A connection or contact at any of these can cause this issue. Since the LBCD is out in the weather, it is a prime candidate for a bad/corroded connection. That was the first issue I troubleshot on my truck. As soon as I would crank the truck, the 12v would fall on it’s nose and open the main ignition relay(12v controls the main ign relay on an A0). They used 24V fir this control on the A1’s… Mine was a bad connection at the polarity box/LBCD…

So if the voltage at both batteries stays good when you turn on the main sw, you need to start measuring along the circuit pathway till you find the voltage drop. The drop is where the problem lies…

 

[D92!]

Yes voltage drop at both posts. I checked batteries with master on all sustain 12.5 volts. And 12.5 at the 12v side of relay or DRIC (dual relay) truck starts and runs fine. Don’t have 24v at the excite lead. A/C condenser fans run constantly I unplugged them did not fix issue also took mil connector LCBD issue stays the same. This truck caught on fire all electrical harnesses and cables were replaced except for the cab harnesses and abs ecu was replaced. Alt. is also new.

 

[Ronmar]

Never heard the cutoff relay assy called the DRIC before. At any rate it sounds like you have a bad connection associated with the relay assy if you are seeing volt drop at the LBCD As that is the next stop after those cutoff relays back by the battery box.

The aux fans running are an interesting clue. If they are running, your main engine fan is also probably engaged. what happens when you activate the fording switch on the top left dash(they should shut off)? That switch bypasses the fan control signal from the ECU. It is reverse logic, the ECU or that fan/fording switch provides 24V to energize the fan control solenoid and the aux fan relay, which keeps the fans OFF/DISENGAGED. When the ECU detects high temp it removes that 24V, which de-energizes the fan solenoid and aux fan relay which ENGAGES the main fan and turns ON the aux fan.

When you turn on the main switch, relays K26(neutral) and K11(alt excite) should energize. Does this happen? If so then the source power from CB77 is OK.

After you start the engine, and it builds 15PSI of oil pressure, the oil pressure switch de-energizes K11(and the oil idiot light). The de-energized contacts of K11(pin 30-87A) then feed the same power from CB77 down to power the alternator regulator and bring the alt online. K11 must be a 5 pin relay for this to work right.

 

[Third From Texas]

I had this happen the other day but was unable to replicate.

I knew there was a thread but damned if I could find it.

Talked with GeneralDisorder and he found this:

Based on this PDF document, the annunciator panel icon lights will enter a chase sequence after losing the data connection to the MMDC for 45 seconds.

https://community.fmca.com/applications/core/interface/file/attachment.php?id=7434

So it would appear you have a connectivity issue between the annunciator panel and the MMDC itself. Connections or wiring would be my guess.

Looks like variations on these units are real common on RV's and trucks. Saw mention of Freightliner using Medallion MDC's, etc.

 

[coachgeo]

I’m currently having this same issue. But I have 12v on the cable that comes from the DRIC to the 12v Batt. Post on the LBCD. When I connect the cable on the post it starts dumping volts when master is turned on. Goes from 12v down to three.

like learning new things..... call me crazy

DRIC?? Dual Relay Interrupt Circuit???

 

[D92!]

Yes that’s what it’s called had a brain fart! This truck has been a nightmare. Currently waiting on a computer for in the cab and the cab harnesses and PDP. So it might be awhile before another update.

 

[D92!]

I had this happen the other day but was unable to replicate.

I knew there was a thread but damned if I could find it.

Talked with GeneralDisorder and he found this:

Thank you! This may help a lot!

 

[Third From Texas]

Thank you! This may help a lot!

The thanks goes to General Disorder.

I used multiple search engines and couldn't find squat on the web on tis topic. I'd even been in some of the RV/CAT forums looking. I'd seen a video of the issue once (don't recall if it was GP or an owner) but never knew what the issue was called nor what it was warning of. Mine only did it once and I've been unable to replicate, but at least I know a few things I can look into now. Machines are supposed to talk to you when they do things like that:

"By your command" or "I'm a Knight Industries 2000"

 

[Ronmar]

The thanks goes to General Disorder.

I used multiple search engines and couldn't find squat on the web on tis topic. I'd even been in some of the RV/CAT forums looking. I'd seen a video of the issue once (don't recall if it was GP or an owner) but never knew what the issue was called nor what it was warning of. Mine only did it once and I've been unable to replicate, but at least I know a few things I can look into now. Machines are supposed to talk to you when they do things like that:

"By your command" or "I'm a Knight Industries 2000"

Yea I recall the running light pattern being discussed, but don’t recall where as it wasn’t relevant to anything I was doing specifically(too many tech assists and limited storage capacity).

 

[Wes11293]

Superman .. need help. Have a m1088a1P2 and replaced Alt and regulator and all relays. My lights are rambler that batteries all tested good and I’m getting good charging on 12v side but the 24v side I’m sitting at 25-26 volts ? What would cause it to charge but not to 28v?