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Operation Mobile Meth Lab Retrieval -12v cummins guys and allison tranny guys welcome.

Here's a really stupid question: have you called and talked to an actual Allison transmission rebuild shop? if they are not assholes, they may tell you the most common problem they see with that transmission. get them talking and take notes. then tell them if you cant fix it easily with a sensor, you will bring it to them. inquire if they can order/sell you parts you may need. This will keep them interested enough to try and help you.

if they are a-hole scammers then all bets are off.
 
Texas97 said:
if the house power is a separate system, why even mess with it? does it have some power or wiring it shares with the transmission? Dont go getting all out in left field before chasing down the main issue. Which appears to be the transmission and its electrical sensors and wiring.

if you can just disconnect the house power at the batteries, thats fine. but dont go disconnecting stuff that isnt broken because when you go to put it back together it may become broken.

Focus on the issue. if you are unsuccessful troubleshooting in the direct transmission wiring then you can start expanding your orbit from there.
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I feel like there's an issue or short or something between house and chassis power. There's a 100 amp fuse off of the battery isolator on the house side that occasionally pops only when the motor is running. I'm not sure why yet. I also can't explain why the only time my ODBII port suddenly came alive again for a few seconds, was when I was hitting the battery boost button.

I'd like to eliminate that extra complexity before I move forward with troubleshooting the rest.. mainly because it's an unknown and I don't want to be wondering in the back of my mind if there's some bullshit short over that that's causing problems with the chassis.
 
87manche said:
here we go on some real information on what makes it tick.

page 13 is your wiring pin out.
next page has all the DTC codes.

according to that voltage problems will trip a check trans light. so it's possible you just need to make your charging system not suck.
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I've actually got that saved to my phone and in the cloud so I could pull it up anywhere on the trip if I needed to. Lots of good info.
 
and not to get off in the weeds, but I've found that a shitty little DSO oscope kit is super handy for pots and speed sensor diag.
and I don't care if I break it, unlike dragging out a nice scope to the car.
 
Texas97 said:
Here's a really stupid question: have you called and talked to an actual Allison transmission rebuild shop? if they are not assholes, they may tell you the most common problem they see with that transmission. get them talking and take notes. then tell them if you cant fix it easily with a sensor, you will bring it to them. inquire if they can order/sell you parts you may need. This will keep them interested enough to try and help you.

if they are a-hole scammers then all bets are off.
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I do have a guy who is super reliable and knows his stuff. I want to be able to tell him what codes I'm getting or I think we'd just be sitting on the phone talking hypotheticals all day.
 
87manche said:
and not to get off in the weeds, but I've found that a shitty little DSO oscope kit is super handy for pots and speed sensor diag.
and I don't care if I break it, unlike dragging out a nice scope to the car.
Click to expand...
This is a bit above my knowledge level- what can I do with a oscilloscope that I couldn't do with a multimeter(I realize there is probably a lot, just don't know enough)?
 
Harry Johnson said:
I feel like there's an issue or short or something between house and chassis power. There's a 100 amp fuse off of the battery isolator on the house side that occasionally pops only when the motor is running. I'm not sure why yet. I also can't explain why the only time my ODBII port suddenly came alive again for a few seconds, was when I was hitting the battery boost button.

I'd like to eliminate that extra complexity before I move forward with troubleshooting the rest.. mainly because it's an unknown and I don't want to be wondering in the back of my mind if there's some bullshit short over that that's causing problems with the chassis.
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Well you have a shitload of problems then. That 100 amp fuse blowing should have been fixed a while ago.
 
Harry Johnson said:
Well yeah. It's a 1980 motorhome with a backyard motor and tranny swap. There's a lot of stuff like that. Plugging away at it one piece at a time.
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Don't take this wrong but I guess I figured you would have fixed some of the glaring gremlins before taking off with two small kids and the wife for a trip.

Routine 100 amp fuse blown would have me tracking that back down instead of just carrying a bag of fuses.

Don't get me wrong, my crawler/ranch truck tends to blow a backup light fuse but it's got one axle in the junkyard and my kids aren't going more than 20 minutes from home in it
 
Texas97 said:
Don't take this wrong but I guess I figured you would have fixed some of the glaring gremlins before taking off with two small kids and the wife for a trip.

Routine 100 amp fuse blown would have me tracking that back down instead of just carrying a bag of fuses.

Don't get me wrong, my crawler/ranch truck tends to blow a backup light fuse but it's got one axle in the junkyard and my kids aren't going more than 20 minutes from home in it
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I hear ya. I did spend a lot of time going through it and we've been on quite a few camping trips up through this. There were some big issues that I found and squashed already. The 100 amp breaker tripping on the house power side seemed to only be wired up for the fridge (it doesn't work when breaker tripped, but everything else seems to?), so I just had it as something I wanted to get around to fixing. I didn't start thinking it might somehow be connected to the chassis side of things until my current trouble. The chassis side of the things has been pretty reliable up until now with the exception of the TPS occasionally dying, which is why I was comfortable doing such a long trip with the family. This isn't even the first time we've done this run to southern California, it has made it down there a few times with no drama (breaker popping, trans crapping out, nothing) a few times before:
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This is actually one of the reasons I'm considering selling it and getting something more reliable- there are a lot of complexities to a motorhome and I don't think I have time to check everything on this one to make sure it's good to go compared to something newer that just works.
 
Harry Johnson said:
This is a bit above my knowledge level- what can I do with a oscilloscope that I couldn't do with a multimeter(I realize there is probably a lot, just don't know enough)?
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seeing the pulses and freqency of VSS sensors and things.
Seeing the pot (tps) output in a graph form so you can see if there's dead spots, rather than just trying to see the voltage sweep on a shitty DMM screen that can't keep up.
checking can bus things.
basically anything digital is more easily diagnosed with an oscope than a multi meter.

JYETech 'DSO Shell' Oscilloscope DIY Kit w/Enclosure & Clip Probe by Nooelec. Low Cost Digital Storage Oscilloscope with 2.4" TFT LCD. Model DSO150 (DSO 150); SKU 15001K: Amazon.com: Industrial & Scientific

JYETech 'DSO Shell' Oscilloscope DIY Kit w/Enclosure & Clip Probe by Nooelec. Low Cost Digital Storage Oscilloscope with 2.4" TFT LCD. Model DSO150 (DSO 150); SKU 15001K: Amazon.com: Industrial & Scientific
www.amazon.com
I power it with a 9 volt battery
 
Surprised no one here knows how to check resistance in a circuit with a voltage drop test.
 
Harry Johnson said:
Can't find the one you linked for sale online, but I did find this one that looks like a slightly different version from the same MFG. Seems to do all the same stuff although I can't wrap my head around how the chassis battery/alternator can charge the house battery without the house battery load also killing the chassis battery, but I'm willing to try it out. What do you think?
InPower ABS3-200A Auxiliary Battery Switch, 200A, 12V, Dual Lug | Waytek
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Yes thats is the new and improved version. abs2 has been superseded by that.

Basically they made it more efficient. moved the grounding to a stud vs on the corner of the mount.

This guy hit the explanation perfectly. The input pin allows you to manually force both batteries together. in cases were your engine battery might be dead or what ever you want to do. but the diodes take care of switching. it disconnects at like 11.9 volts
87manche said:
diodes.

they're like check valves for electricity.
pretty standard shit.

edit:
some also are voltage sensing relays, connect the house to the chassis when it senses over 13V or whatever.
that one appears to be a solid state voltage sensing switch.
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A_G said:
Yes thats is the new and improved version. abs2 has been superseded by that.

Basically they made it more efficient. moved the grounding to a stud vs on the corner of the mount.

This guy hit the explanation perfectly. The input pin allows you to manually force both batteries together. in cases were your engine battery might be dead or what ever you want to do. but the diodes take care of switching. it disconnects at like 11.9 volts
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Badass. Ordered.
 
shortbus4x4 said:
How do you know?:grinpimp:
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fire!
Harry Johnson said:
This is actually one of the reasons I'm considering selling it and getting something more reliable- there are a lot of complexities to a motorhome and I don't think I have time to check everything on this one to make sure it's good to go compared to something newer that just works.
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newer means you'll be dealing with the same issues, just add some horrible structural fuckery and water leaks and emissions bullshit to the pile

your description of the old sensor falling apart when you bolted it back on makes me think they might be getting cooked, is the exhaust or a trans cooler line or even just airflow off the exhaust blowing back over the bastard?
 
[486] said:
newer means you'll be dealing with the same issues, just add some horrible structural fuckery and water leaks and emissions bullshit to the pile

your description of the old sensor falling apart when you bolted it back on makes me think they might be getting cooked, is the exhaust or a trans cooler line or even just airflow off the exhaust blowing back over the bastard?
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I dunno, I've been eyeing some of the super c chassis and those seem like they would be much more reliable since it's basically a 5500 chassis with a motorhome on its back.

As for the sensor, I think that was happening to some of them, even before whatever my new issue is. They're right there on the side of the block and there's not a lot of airflow because motorhome. I was thinking about making a mount for one of these somewhere else and just running a throttle cable off of the pedal to move it. Not sure how much fab work I want to put I to it tho
 
Harry Johnson said:
This is actually one of the reasons I'm considering selling it and getting something more reliable- there are a lot of complexities to a motorhome and I don't think I have time to check everything on this one to make sure it's good to go compared to something newer that just works.
Click to expand...

there is no such thing as a motorhome that 'just works' to be honest the new ones have the most problems.

it looks like a bitchen RV, its got character. if you like it, and it doesn't leak, keep it. fix the problems. nothing worse than dropping money on a whole new set of problems.
 
Harry Johnson said:
I dunno, I've been eyeing some of the super c chassis and those seem like they would be much more reliable since it's basically a 5500 chassis with a motorhome on its back.

As for the sensor, I think that was happening to some of them, even before whatever my new issue is. They're right there on the side of the block and there's not a lot of airflow because motorhome. I was thinking about making a mount for one of these somewhere else and just running a throttle cable off of the pedal to move it. Not sure how much fab work I want to put I to it tho
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maybe duct some air to it from the front using dryer duct parts
 
tracyb said:
there is no such thing as a motorhome that 'just works' to be honest the new ones have the most problems.

it looks like a bitchen RV, its got character. if you like it, and it doesn't leak, keep it. fix the problems. nothing worse than dropping money on a whole new set of problems.
Click to expand...
It is really cool. The conundrum is that even though I want to sell it now, I wouldn't sell it to someone without fixing these issues and as I fix it, I'll probably like it again. The wife is pretty adamant about not taking the kids in it anymore, fixed or not... so we'll see.
 
Harry Johnson said:
It is really cool. The conundrum is that even though I want to sell it now, I wouldn't sell it to someone without fixing these issues and as I fix it, I'll probably like it again. The wife is pretty adamant about not taking the kids in it anymore, fixed or not... so we'll see.
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$3.50:flipoff2:
 
Not sure how much applies but the allison transmissions in the pickup trucks are very sensitive to battery voltage. I've had several shift wierd, limp mode, won't go into gear if the batteries are screwed up or the alternator starts doing weird things. Look for AC ripple on the alternator output, it'll kill batteries and cause digital electronics to freak out.
 
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