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Mav’s M1088A1 Conversion
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Ronmar
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It is either a gauge temp sensor or a temp switch or an ECU coolant temp sensor.
On the A0, they put a gauge sender on the rear side of the housing(upper port), off of a T that circulates coolant to the expansion tank. The heater feed is the lower port, both can be seen upper left in your first pic. On the inboard side of the housing, opposite to where this sensor is, they put a 230F switch that drives the high temp light in the idiot light panel. On the 3116, there isn’t even a port in this outboard location…
The 3126 adds a engine coolant temp sensor to the mix. On the later A1s, I believe the integrated bussed gauge package gets its coolant info from the data bus to drive the gauge, so back to 2 sensors? On the earlier trucks, you may have 3 sensors on that housing. The 230F switch is usually a Nason and will say so on its label, and it has a larger body like the low oil pressure switch. This looks like a resistive temperature sensor, so either ECU or gauge sensor would be my guess.
Unplug it and see what happens, either the gauge will quit or the check engine light will come on…
On the A0, they put a gauge sender on the rear side of the housing(upper port), off of a T that circulates coolant to the expansion tank. The heater feed is the lower port, both can be seen upper left in your first pic. On the inboard side of the housing, opposite to where this sensor is, they put a 230F switch that drives the high temp light in the idiot light panel. On the 3116, there isn’t even a port in this outboard location…
The 3126 adds a engine coolant temp sensor to the mix. On the later A1s, I believe the integrated bussed gauge package gets its coolant info from the data bus to drive the gauge, so back to 2 sensors? On the earlier trucks, you may have 3 sensors on that housing. The 230F switch is usually a Nason and will say so on its label, and it has a larger body like the low oil pressure switch. This looks like a resistive temperature sensor, so either ECU or gauge sensor would be my guess.
Unplug it and see what happens, either the gauge will quit or the check engine light will come on…
so @Ronmar it looks like the “thermal resistors” listed on MME website. could it be a temp sensor for ether system mounted on the thermostat housing?
edit: I will have to check the crossover tube to see if there is a sensor mounted in that location.
edit: I will have to check the crossover tube to see if there is a sensor mounted in that location.
Ronmar
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I would suspect it is the sensor for the ECU. I just went to look for wire/connector info and discovered the A1 and A1R diagrams don’t show the engine temp sensor connection to the ECU…
got wire numbers off that sensor and the one to the rear of the housing?
got wire numbers off that sensor and the one to the rear of the housing?
There are two sensors on the aft side of the housing:
inboard sensor - P41
outboard sensor (Nason) - P37
broken sensor I mentioned previously - P42
Ronmar
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Thats how i would have found it... the cat sensors are not listed in the mil documentation and the cat coolant sensor does not appear to have a pigrail...@Ronmar I found it, it is the ether sensor mounted on the housing on the A1 trucks. Found it by searching the wire tag in the TM, I appreciate the tip on that!
If it is for the ether, then it is probably a 35F switch(mine was)...
Is there any harm in running the truck with the CTIS controller unplugged? I noticed there’s a CTIS OFF light on the cluster but it’s not illuminated, assumed that would illuminate if the controller is removed so just wanted to make sure the tires aren’t going to endlessly try and inflate or something crazy.
coachgeo
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with truck off..... unscrew the cannon plug's ring and pull / leave it off. Your good to go.
PS- you should do this prior to jump starting the truck as well. There is enough empirical evidence to show this can brick the CTIS controller. After truck is running good enough to turn off and you know it will re-start...... then with truck off put the cannon connector back and screw the ring home.
Ronmar
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Should be no problem running without it. Are you sure that dash light is “CTIS OFF“? There is a CTIS overspeed light in the dash and CTIS will light this light when you go too fast for a particular tire pressure, then it will initiate an automatic inflate to get to the appropriate pressure for your speed.
in order for the tires to inflate, the Control solenoid must close and stay closed to seal the system. NOTHING can happen unless control is sealed!. Then the inflate solenoid must open to add air, so it would take 2 failures in tandem to cause a rogue inflate…
The Pressure Control Unit(PCU) uses pilot operated control valves. The solenoids manipulate a little bit of air to move a valve core that can open and close large bore valves. What I discovered, and have replicated on a few PCU assemblies now, is that if you only close control, supply starts to leak very slowly into the manifold. After about 25-30 seconds the system pressure builds above 5PSI and the wheel valves will open. Since the PCU manifold is at 5 and the tires are at 55+, the dump valves immediately start to dump tire air, which is a pretty hard noise to miss. The dump valves are designed to feedback some of the tire air towards the PCU side, so the manifold side builds up air quickly. When the PCU side of the dump valve equals the tire side the dump valves will close(you can hear the dump slowing down as this happens. This takes about 20-30 seconds.
so a shorted control will cause a 20-30 sec un-commanded dump, and of course a shorted supply would dump anything above 85 PSI in the wet tank, so also pretty obvious. The likley hood of them happening together is very very slight IMO…
in order for the tires to inflate, the Control solenoid must close and stay closed to seal the system. NOTHING can happen unless control is sealed!. Then the inflate solenoid must open to add air, so it would take 2 failures in tandem to cause a rogue inflate…
The Pressure Control Unit(PCU) uses pilot operated control valves. The solenoids manipulate a little bit of air to move a valve core that can open and close large bore valves. What I discovered, and have replicated on a few PCU assemblies now, is that if you only close control, supply starts to leak very slowly into the manifold. After about 25-30 seconds the system pressure builds above 5PSI and the wheel valves will open. Since the PCU manifold is at 5 and the tires are at 55+, the dump valves immediately start to dump tire air, which is a pretty hard noise to miss. The dump valves are designed to feedback some of the tire air towards the PCU side, so the manifold side builds up air quickly. When the PCU side of the dump valve equals the tire side the dump valves will close(you can hear the dump slowing down as this happens. This takes about 20-30 seconds.
so a shorted control will cause a 20-30 sec un-commanded dump, and of course a shorted supply would dump anything above 85 PSI in the wet tank, so also pretty obvious. The likley hood of them happening together is very very slight IMO…
Got the aux tranny cooler deleted (for now?) and the toolbox removed. Tomorrow I will get the spare tire carrier and intake removed then on to fabbing up a storage compartment to move the airtanks and dryer aft to make room for second fuel tank.
ramdough
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Where are you putting the air tanks?
I have been wondering myself where a better place would be.
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I have been wondering myself where a better place would be.
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I’m only just moving them aft on the driver side frame rail to allow for a second OEM fuel tank to be added on that side. Batteries I haven’t quite decide yet.
There will be space above the drivers side fuel tank for a compartment made with a slide out drawer where I can store vehicle/habitat batts together. I don’t think this will be an issue with diesel fuel in open air below it but just want to make sure that’s going to be safe first.
There will be space above the drivers side fuel tank for a compartment made with a slide out drawer where I can store vehicle/habitat batts together. I don’t think this will be an issue with diesel fuel in open air below it but just want to make sure that’s going to be safe first.
coachgeo
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Interesting.... didnt realize that model did not have the helecopter lift points on the cradle that holds the air cleaner and spare tire etc.
Oh those have already been removed.
Should this cab mount be this loose or is there a missing bushing between the two? I’m assuming the latter. I’m feeling like it’s contributing to a lot of the clunking in the cab while driving (i know some probably coming from airbags as well).
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Mine had the same problem, whatever was under there crumbles away, you can actually see it there piled up on the seam of your cab. None of the parts breakdowns that I could find actually show that bushing, I think it is actually sprayed in there. I replaced mine with a bunch of rubber O-rings and then glued it all together with “The Right Stuff” RTV.
It’s holding together just fine so far and the cab slop is gone now and much quieter. I also noticed that my latch wasn’t sitting quite flat and so I followed the procedure in the TM to adjust it. Now the cab has most of the weight on the two pegs on the side of the air-ride frame. This completely silenced the horrible squeaking I was getting from the cab. Turns out when the latch wasn’t flat, it was actually supporting the weight of the cab rather then the two pins on the side of the air-ride frame. The resultant clearance created was responsible for a terrible squeaking due to the vibration present.
What do you mean by the “two pins on the side of the air ride frame?