New Rig

[gslader]

So I picked up a 2003 M1078a1 last week with 8,700 miles on it. What a learning experience this has been so far - all part of the journey. I picked it up late on a Friday in Idaho and drove it 500 miles overnight to California on what was a relatively uneventful drive. The prior owner installed the higher ratio gears and it seems to cruise pretty happily in the upper 60s. It also has an aftermarket 12v material handling crane and 100 gallon transfer tank (plumbed but not currently wired) - other than that it is pretty stock. The highlight so far was that the AHU had no hydraulic fluid and would not raise the cab (obviously) when I purchased it so I assumed it had a massive leak as many have experienced. However, after filling with hydraulic fluid it raised the cab and lowered the spare tire and I have not yet seen any visible leaks after 24 hours (fingers crossed).

Here are the things I’ve checked so far and would appreciate any input for things I missed (which I’m sure is a lot):
- Checked all fluid (all were good except AHU - see below)
- Filters (all replaced July 2021 with the exception of fuel/water filter)
- Can find no record of air dryer being serviced so have rebuild kit on hand - how often should the air system exhaust? It happens on mine every 10 - 15 mins while driving; is that too often?
- Grease Ports: All grease ports are taking grease right now
- U-joints: no discernible play
- Gear case: No visible cracks
- Cab bushings: Driver side cab bushing is cracked significantly - will need to address
- Cab Air-ride Springs: They inflate but it doesn’t feel right, it might be the leveling switch is faulty and I can also hear air escaping from them after shut down so I will likely just upgrade to MME’s air ride set-up

On my radar but haven’t checked yet:
- Drive-shaft balancing
- Check service planetary hubs
- Drivers door lock requires that the key be turned twice to open the door - given how often these door latches/locks fail and their track record I assume this is failing but still operable and will need to be replaced at some point

Known issues:
- Fuel guage is pegged at full; which I believe means an open circuit; need to trouble shoot
- There is a hydraulic line off what I believe is the power steering unit (just saw it this evening) that appears to have been pinched and while it is not leaking it should be replaced
- Ether bottle inoperative: Either valve is broken or empty bottle - new bottle is on order

Work done so far - very pedestrian:
- New weather stripping on both doors
- Replaced headlights with Truck-Lite 27270c


I’ve started to do some work on it and have been reading the TM like the Bible it is. There are a few things that I am still scratching my head over though. I picked up four new 6TL batteries and was in the process of installing them when I realized a) I need to make new battery leads and b) the existing batteries are wired incorrectly (see below). The truck seems to run fine with the batteries in the current configuration but interesting the front set of batteries indicates 12.8v and the rear set of batteries indicates 13.6v. When I load tested the batteries the rear set load tested fine while the front two indicated they should be replaced. Anyone seen this before?


Also, I have seen several videos of truck cabs with a 12v switch on the instrument panel (again below) but it isn’t referenced in the TM (I only have a0 manual) and I can’t find reference to it when I google. Can anyone help out with what it is for?



I also have a safety toggle switch next to the STE/ICE-R port. In the A0 TM in indicates there is a reset switch there but it doesn’t show the form factor that I have. I assume that is what it is but any confirmation would be great.

 

[Ronmar]

The air dryer purges every time the compressor reaches full pressure and unloads. So the more air you use the more often it purges. The air compressor cycles on around 105 PSI and should cycle off around 125 PSI. It senses the wet tank pressure to do this. If the front and rear brake pressures are not dropping between cycles, it indicates the wet tank is feeding the air. If the cab airbags are leaking that could be a cause of the leak. in a perfect world, the compressor would only cycle after you use enough air with the brakes to knock a gauge down to 100 PSI. So chase your leaks.

I would service the dryer at least annually. It depends on how much air it processes and the overall condition of your compressor(how much oil is getting past the compressor rings). The old style doesn’t necessarily need a rebuild kit as you can clean/wash the media with a degreasing detergent, rinse and re-install it. Here is a link to a video I did on this procedure.

You have an A1, not an A0, they changed a few things in the wiring. You can get an A1 electrical schematic here on SS.

FMTVA1 Electrical Schematics

the switch at the gauge switches the gauge between the 12v and the 24v power systems…

That red switch is a master power switch(Disconnects main power relays in box behind battery box and also removes ignition power). There are also 3 remote switches inboard of the passenger tire that control battery, ignition power and crank the starter…

 

[gslader]

The air dryer purges every time the compressor reaches full pressure and unloads. So the more air you use the more often it purges. The air compressor cycles on around 105 PSI and should cycle off around 125 PSI. It senses the wet tank pressure to do this. If the front and rear brake pressures are not dropping between cycles, it indicates the wet tank is feeding the air. If the cab airbags are leaking that could be a cause of the leak. in a perfect world, the compressor would only cycle after you use enough air with the brakes to knock a gauge down to 100 PSI. So chase your leaks.

I would service the dryer at least annually. It depends on how much air it processes and the overall condition of your compressor(how much oil is getting past the compressor rings). The old style doesn’t necessarily need a rebuild kit as you can clean/wash the media with a degreasing detergent, rinse and re-install it. Here is a link to a video I did on this procedure.

You have an A1, not an A0, they changed a few things in the wiring. You can get an A1 electrical schematic here on SS in the present conflict vehicles manual section near where the A0 manuals are located. That red switch is a master power switch(Disconnects main power relays in box behind battery box and also removes ignition power). There are also 3 remote switches inboard of the passenger tire that control battery, ignition power and crank the starter…

Thanks for the guidance on the air system and on the electronics. I saw those three switches behind the passenger tire and had them on my list to research - you just solved that for me. Thank you. I had read about some external controls for maintenance purposes - I assume that is what those three switches are for?

 

[Lostchain]

So I picked up a 2003 M1078a1 last week with 8,700 miles on it. What a learning experience this has been so far - all part of the journey. I picked it up late on a Friday in Idaho and drove it 500 miles overnight to California on what was a relatively uneventful drive. The prior owner installed the higher ratio gears and it seems to cruise pretty happily in the upper 60s. It also has an aftermarket 12v material handling crane and 100 gallon transfer tank (plumbed but not currently wired) - other than that it is pretty stock. The highlight so far was that the AHU had no hydraulic fluid and would not raise the cab (obviously) when I purchased it so I assumed it had a massive leak as many have experienced. However, after filling with hydraulic fluid it raised the cab and lowered the spare tire and I have not yet seen any visible leaks after 24 hours (fingers crossed).

Here are the things I’ve checked so far and would appreciate any input for things I missed (which I’m sure is a lot):
- Checked all fluid (all were good except AHU - see below)
- Filters (all replaced July 2021 with the exception of fuel/water filter)
- Can find no record of air dryer being serviced so have rebuild kit on hand - how often should the air system exhaust? It happens on mine every 10 - 15 mins while driving; is that too often?
- Grease Ports: All grease ports are taking grease right now
- U-joints: no discernible play
- Gear case: No visible cracks
- Cab bushings: Driver side cab bushing is cracked significantly - will need to address
- Cab Air-ride Springs: They inflate but it doesn’t feel right, it might be the leveling switch is faulty and I can also hear air escaping from them after shut down so I will likely just upgrade to MME’s air ride set-up

On my radar but haven’t checked yet:
- Drive-shaft balancing
- Check service planetary hubs
- Drivers door lock requires that the key be turned twice to open the door - given how often these door latches/locks fail and their track record I assume this is failing but still operable and will need to be replaced at some point

Known issues:
- Fuel guage is pegged at full; which I believe means an open circuit; need to trouble shoot
- There is a hydraulic line off what I believe is the power steering unit (just saw it this evening) that appears to have been pinched and while it is not leaking it should be replaced
- Ether bottle inoperative: Either valve is broken or empty bottle - new bottle is on order

Work done so far - very pedestrian:
- New weather stripping on both doors
- Replaced headlights with Truck-Lite 27270c
View attachment 858986

I’ve started to do some work on it and have been reading the TM like the Bible it is. There are a few things that I am still scratching my head over though. I picked up four new 6TL batteries and was in the process of installing them when I realized a) I need to make new battery leads and b) the existing batteries are wired incorrectly (see below). The truck seems to run fine with the batteries in the current configuration but interesting the front set of batteries indicates 12.8v and the rear set of batteries indicates 13.6v. When I load tested the batteries the rear set load tested fine while the front two indicated they should be replaced. Anyone seen this before?
View attachment 858988

Also, I have seen several videos of truck cabs with a 12v switch on the instrument panel (again below) but it isn’t referenced in the TM (I only have a0 manual) and I can’t find reference to it when I google. Can anyone help out with what it is for?

View attachment 858989

I also have a safety toggle switch next to the STE/ICE-R port. In the A0 TM in indicates there is a reset switch there but it doesn’t show the form factor that I have. I assume that is what it is but any confirmation would be great.

View attachment 858991

Nice score! I actually saw this one advertised on Craigslist when I was looking… The red switch is the main power switch. I would flip that off to prevent power drain when not using the truck. On my A1, for example, the light controller remains powered up until I flip that off. When I flip it on or off I hear a clunk back by the batteries so I am assuming it controls a battery relay. Sucks not having the A1 manuals available.

 

[INFChief]

The air dryer purges every time the compressor reaches full pressure and unloads. So the more air you use the more often it purges. The air compressor cycles on around 105 PSI and should cycle off around 125 PSI. It senses the wet tank pressure to do this. If the front and rear brake pressures are not dropping between cycles, it indicates the wet tank is feeding the air. If the cab airbags are leaking that could be a cause of the leak. in a perfect world, the compressor would only cycle after you use enough air with the brakes to knock a gauge down to 100 PSI. So chase your leaks.

I would service the dryer at least annually. It depends on how much air it processes and the overall condition of your compressor(how much oil is getting past the compressor rings). The old style doesn’t necessarily need a rebuild kit as you can clean/wash the media with a degreasing detergent, rinse and re-install it. Here is a link to a video I did on this procedure.

You have an A1, not an A0, they changed a few things in the wiring. You can get an A1 electrical schematic here on SS.

FMTVA1 Electrical Schematics

the switch at the gauge switches the gauge between the 12v and the 24v power systems…

That red switch is a master power switch(Disconnects main power relays in box behind battery box and also removes ignition power). There are also 3 remote switches inboard of the passenger tire that control battery, ignition power and crank the starter…

RE: the 12V dash switch. Is that a ‘latching’ circuit where by pressing the switch changes to 12V? Or is it a ‘momentary’ switch where once released it no longer does anything? What does that switch do; what does it activate & why? TIA.

 

[Ronmar]

RE: the 12V dash switch. Is that a ‘latching’ circuit where by pressing the switch changes to 12V? Or is it a ‘momentary’ switch where once released it no longer does anything? What does that switch do; what does it activate & why? TIA.

I believe that dash 12v switch allows you to measure the 12V side of the electrical power system. I suspect it is momentary and when released monitors the 24v side of the system Like the 24v gauge does in the A0. Looking at the diagram which appears to be drawn incorrectly, I believe that is actually a 12V gauge with dual markings, and the switch shifts both the sense line and the reference line between 24V and 12V, but there is no ground reference drawn to the gauge or switch…

it could also be a dual coil/input gauge, but with no ground ref indicated on the drawing, I cannot tell…