Paging Dr Ronmar, etc

[Mullaney]

MMDC ??

Metal Marking Device Controller?
Monkey Mash Dog Collar?
My Mother Despises Congress?

.
I particularly like the third in the list...
My Mother Despises Congress

 

[chucky]

MASS MEDIA DISGUISE CORRUPTION ! MY MENTAL DISEASE CONTROLLER ! MY MOTHER DRIVES CHEVROLET ! AND this ones for you 3rd MOST MOTHERS DESPISE CORPUS ! MAD MOTHERS DENOUNCE CORPUS ! MAN MAKES DAUGHTER COLAPSE ! MAN MAKES DAUGHTER CORRUPT !

 

[Third From Texas]

I would monitor the supply voltage to the MMDC using both power and ground from it's harness for my gauge. If that looks normal I would scope the power (+7v) and data lines to the instruments and see what I could discern from that.

The gauges you note are "blinking out" have no connections except to the MMDC itself (2001A - Instrument Data, 2002A - Instrument Power +7v, 3004A - Instrument Ground) and a single wire from the lighting circuits for illumination (1908A - Light +12v).

The only possibilities I see are:

1. Low/dirty power or poor ground to the MMDC = bad data being fed to the instrument bus.

2. Some kind of interference on the J1587 data bus. MMDC and CTIS are both on this bus.

3. MMDC itself has problems - can't see how this would relate to the CTIS but they are near enough - could the harness being plugged in or not change the strain on the MMDC connectors?

Awesome stuff. At least I have a place to start now.

Thanks !

 

[Ronmar]

What General Disorder said…. I suspect it is interfering with the data bus…. If it works fine without it connected, that is a likely scenario. Either it is the issue, or there is a buss issue and CTIS is the straw breaking the camels back…

Sadly 5 solids is an internal fault, so it definitely has an issue. I have not heard of anyone recovering/restoring one, so you will need to source another one…

 

[Third From Texas]

What General Disorder said…. I suspect it is interfering with the data bus…. If it works fine without it connected, that is a likely scenario. Either it is the issue, or there is a buss issue and CTIS is the straw breaking the camels back…

Sadly 5 solids is an internal fault, so it definitely has an issue. I have not heard of anyone recovering/restoring one, so you will need to source another one…

Rgr all.

If it's the controller I'm likely going to go with a manual control or possibly an Arduino-based solution. The OEM controllers simply don't seem to last (this one didn't have 10K miles on it yet). Seems most every truck has had issue with them at some point so I wouldn't really be interested in replacing mine with another. I'd maybe be willing to pay $50 for NOS if I stumbled across one but I think I'd rather have a more rugged solution....

 

[Third From Texas]

I knew I'd read a similar problem somewhere...

RESOLVED: Dash gauge issues when CTIS plugged in?

Hello all! Have been lurking on the forums for a bit and recently picked up an 05 1078. So far has been a great truck and limited issues. However since I bought it I have had one issue I cannot seem to sort out. Whenever the CTIS ECU is plugged in I loose oil pressure on the dash and sometimes...

www.steelsoldiers.com

 

[Third From Texas]

Here's his solution. This is exactly my situation to the letter...

RESOLVED: Dash gauge issues when CTIS plugged in?

Hello all! Have been lurking on the forums for a bit and recently picked up an 05 1078. So far has been a great truck and limited issues. However since I bought it I have had one issue I cannot seem to sort out. Whenever the CTIS ECU is plugged in I loose oil pressure on the dash and sometimes...

www.steelsoldiers.com

 

[GeneralDisorder]

FYI:

MMDC = Medallion Marine Data Concentrator.

Medallion is the manufacturer. The "MDC" product line was developed in partnership with Malibu ski boats. It was further developed for military applications where it needs to perform in similar wet environments.

 

[Ronmar]

Here's his solution. This is exactly my situation to the letter...

RESOLVED: Dash gauge issues when CTIS plugged in?

Hello all! Have been lurking on the forums for a bit and recently picked up an 05 1078. So far has been a great truck and limited issues. However since I bought it I have had one issue I cannot seem to sort out. Whenever the CTIS ECU is plugged in I loose oil pressure on the dash and sometimes...

www.steelsoldiers.com

Except the only thing under the pax dash with 1/4” lines is the fan control solenoid valve… dont see a leak there causing CTIS issues…

i should add that the A1R appears to have added a pressure reg in there somewhere to limit air pressure to the fan control, but still don't see a connection to the issue he was experiencing…

 

[Third From Texas]

i should add that the A1R appears to have added a pressure reg in there somewhere to limit air pressure to the fan control, but still don't see a connection to the issue he was experiencing…

Yeah, my air horn pulls from the fan supply. And when the fan is on, the horn won't work (which happens a LOT at the beach, lol).

So yeah, I need to fix that too....

 

[Ronmar]

Yeah, my air horn pulls from the fan supply. And when the fan is on, the horn won't work (which happens a LOT at the beach, lol).

So yeah, I need to fix that too....

Sounds like you are pulling from the fan solenoid outlet, not the supply

 

[GeneralDisorder]

Yeah, my air horn pulls from the fan supply. And when the fan is on, the horn won't work (which happens a LOT at the beach, lol).

So yeah, I need to fix that too....

On my truck the front air tank had nothing connected to the center port at the back of the tank - just a 1/2 NPT brass allen plug. I plumbed my air horn solenoid to this port to avoid unnecessary changes to the air system and unwanted consequences. It's also plumbed with 3/8 OD tubing so the horn is LOUD AF. 125 db.

 

[ramdough]

Yeah, my air horn pulls from the fan supply. And when the fan is on, the horn won't work (which happens a LOT at the beach, lol).

So yeah, I need to fix that too....

Don’t worry, when your fan is on, everyone can hear you coming….


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