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Old 08-08-2018, 04:00 PM   #1
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VIM Wiring help needed.

I have a 1995 Monaco Windsor with MD3060 and I'm trying to trace why my Pacbrake doesn't work.
From the solenoid in my fuse panel to the air solenoid all is good. The issue seems to be from my VIM to who knows where.
The solenoid in the VIM for the Pac doesn't energize. The 12v on the coil is there but the other side, assuming ground, leaves the VIM into a mass of bundled wires. The solenoid checks out good.

I pulled the solenoid and jumped the contact points and the Pac works. So it's something I'm overlooking or the stupid cruise control (doesn't work) that's preventing it to energize....

The line i'm trying to trace is the B1/M1 out of the VIM. Unfortunately the only diagram I came up with is the part of schematic below. Would any one have more info to help me out?


By the way the floor pedal for the PAc works because it downshifts the tranny!

Hope this was clear enough
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Old 08-09-2018, 04:00 AM   #2
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Sounds like you've checked it out well. Attached is a simplified drawing I got while troubleshooting my exhaust brake.
So, if I remember correctly, I had to be moving above like 15 mph before the brake would work. The switch had to be on and then the throttle switch was in charge - if it felt the pedal (as in foot off the pedal) it would activate the brake. If it didn't feel the pedal it would not activate.
When activating my tranny tries to go to 2nd gear but I hear that can be programmed.
I don't know how the cruise control would affect operation - my cruise moves the pedal, which should cause the same operation.
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Old 08-09-2018, 08:48 AM   #3
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Quote:
Originally Posted by RKins View Post
Sounds like you've checked it out well. Attached is a simplified drawing I got while troubleshooting my exhaust brake.
So, if I remember correctly, I had to be moving above like 15 mph before the brake would work. The switch had to be on and then the throttle switch was in charge - if it felt the pedal (as in foot off the pedal) it would activate the brake. If it didn't feel the pedal it would not activate.
When activating my tranny tries to go to 2nd gear but I hear that can be programmed.
I don't know how the cruise control would affect operation - my cruise moves the pedal, which should cause the same operation.
Thx for the reply Rick.

My Pacbrake doesn't have an on/off button only a foot switch. I had seen that diagram and looked high and low for any kind of switch attached to the throttle pedal or linkage and found nothing.
Your point about having to be in motion in order to power the Pac solenoid is a possibility, I'm just not sure where it would get the info. From the Allison ECU?
I'm obviously overlooking something since it wouldn't make sense to be able to activate the Pac while pressing on the fuel pedal or having the cruise control on. There is a solenoid in the "fuse panel" marked "cruise brake cutoff".
I'm going to give Pac a call and see if they can shed light on whether the RV needs to be rolling to activate the VIM solenoid....
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Old 08-10-2018, 12:31 PM   #4
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I posted a thread here on my PAC brake and got some good info. A lot of people tried to help. I'll see if I can find it.
I think your foot pedal is the on/off switch.

I know what you mean about the switch on the throttle. I know I had one because "it" is what controls everything and lets the system know if there is throttle or not. I could see the tranny start it's down shift selection when I let off the pedal, so I knew my switch was working but the mechanic said he couldn't find one, so he put his own in. It's supposed to be at the end of the throttle linkage on the engine.
The tranny is involved with sensing movement and transmits that through, I'm guessing the tranny ECU, to the VIM. My VIM is on the genny side of the firewall - it's a 6" square box full of relays - not a lot of engineering in there.


Edit: Here is the thread PAC Brake problem
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Old 08-13-2018, 08:17 PM   #5
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Quote:
Originally Posted by RKins View Post
I posted a thread here on my PAC brake and got some good info. A lot of people tried to help. I'll see if I can find it.
I think your foot pedal is the on/off switch.

I know what you mean about the switch on the throttle. I know I had one because "it" is what controls everything and lets the system know if there is throttle or not. I could see the tranny start it's down shift selection when I let off the pedal, so I knew my switch was working but the mechanic said he couldn't find one, so he put his own in. It's supposed to be at the end of the throttle linkage on the engine.
The tranny is involved with sensing movement and transmits that through, I'm guessing the tranny ECU, to the VIM. My VIM is on the genny side of the firewall - it's a 6" square box full of relays - not a lot of engineering in there.


Edit: Here is the thread PAC Brake problem
Hey thanks for the input.
I'll start from the top. I had brought the bus to work to do the service on it and ended up bringing it home to do it. I have no tools there (not a mechanic there, but it's a Case dealership so BIG garage) So I brought it home.
On the way home the used the Pac and after the corner it was dead as a mitt no boost. Made it home 10km and parked it. I suspected it might be a fuel problem so I had changed out the filters and oil too. Then I decided to take a look at the Pac since I was never sure it was really working. Tranny downshifted and it felt like the bus was slowing but I wasn't sure. So I popped the bed and started looking if it was working when I found the two wires taped up.
Found the post you included and saw the VIM and the wiring, dug in found VIM, relay and wiring. Pulled the VIM apart and saw it needed a negative to energize the Pac relay which in turn gave gogo juice the Pac relay in the dash. Sent 12v from the dash Pac relay directly to the air solenoid and it worked! So after calling Pacbrake to find out if the Allison ECU reads a speed to activate the VIM relay... WASTED TECH CALL "well you're RV is 25 years old so it can't...." THANKS FOR NOTHING!!!
Check fuses and relays on VIM good, changed out the PAc dash relay and road tested er. Pull away from the stop and we have BOOST! Next step test Pacbrake, let off gas and press PacPedal, downshift....and powers down.
Get to the stop and.............NO POWER. Get home and lift bed and see the Pac in the closed position. Decide I'll wait till it cools to pull it off, duh.
Come back out an hour later and it's OPEN.
This is the Pac I redid last year that was seized beyond belief. I managed the remove the shaft and changed out the seized cylinder. It was working great and I had used the "special" PacOil to lube it too!. Pulled it apart and the shaft was binding a little bit. I pulled it out with just a little resistance and cleaned out the bore, tweeked the shaft a tiny bit and reassembled. She's back in the hole with a switch in the engine bay to check it once and a while and make it easy to operate while lubing. I also installed leads from the Pac dash relay to power a light that will let me know 12v is on it's way to the air solenoid.
Lesson learned, I'm really starting to know this rig....lol

I have NOT tackled the cruise control yet, our plans are mostly local camping for the rest of the season. Maybe this fall i'll feel more like looking at it.

Thx!
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Old 08-14-2018, 04:34 AM   #6
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Yeah I got the same answer when I called PacBrake TS - like they didn't want to talk to anyone but a technician.
So it sounds like it started working - open at first and you had boost/power and then when you pressed the button and took foot off throttle the tranny downshifted and the brake closed.

But then you lost me? Did it stay closed so you had no power?
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Old 08-16-2018, 07:48 PM   #7
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Quote:
Originally Posted by RKins View Post
open at first and you had boost/power and then when you pressed the button and took foot off throttle the tranny downshifted and the brake closed. Did it stay closed so you had no power?
Correct the Pac flap stayed closed even though the solenoid stopped feeding air.
Like I said the crossshaft wasn't perfectly straight. There was also the setscrew that keeps the shaft centered in the bore that I replaced with a bolt with a pointed tip had worked itself loose. The bolt didn't have anything to do with the binding but I replaced it with a longer bolt with a jam nut.

I'll pull the Pac off this winter and have a new shaft made localy. I don't think Pac has any parts for this old model and it's a simple enough shaft to make.
For now it's lubed up and working great and ready for the weekend!
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Old 08-17-2018, 03:53 AM   #8
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Ahhh, I understand now.
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'08 Jeep GC Overland.
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Old 08-19-2018, 06:54 PM   #9
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Back for a great weekend with people I've been camping with for almost 35 years!
So A few things that are confirmed about the wiring of the Pacbrak

With the addition of my "activated" light I know when the air solenoid is getting juice. It's working as it should and the Pac does release when the speed is below a certain speed 10-15mph.
Now I'm not sure what engineer designed the pedal configuration, but I suspect he thought everyone wore high heels or had size 15 feet. I'll take a look to see if the pedal assembly can be lowered. Barefoot with my heel touching the floor my big toe is at the very bottom of the fuel pedal.

My next project will be the cruise control. Tear the original out of see if I can muster the will power to trace the wiring AFTER removing the dash. It would seem the unit resided there.

Despite being parked among $70-500K units and 5ths, I'm pretty happy with the old girl for what I paid.
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Old 09-05-2018, 04:13 PM   #10
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Alterstate

I did not see if you found the on and off switch for the Pac Brake on the dash. There really should be one because if there is ice or snow, you do not want to have the transmission automatically kick down to lower gears at higher speeds which happens during the exhaust brake operation.
Enjoy your camping!!! And have a great day!
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Old 09-06-2018, 07:49 PM   #11
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Quote:
Originally Posted by Allisonman View Post
I did not see if you found the on and off switch for the Pac Brake on the dash. There really should be one because if there is ice or snow, you do not want to have the transmission automatically kick down to lower gears at higher speeds which happens during the exhaust brake operation.
Enjoy your camping!!! And have a great day!
Nope there is none, she's hardwired to work when the speed is above and shut off at I'll say 15mph.
IF I redo the dash, cause it has the "screwed up screw hole" syndrome I'll add a switch with "activated" light next to it. I'm trying to get the courage to strip it and redo it in powder coated aluminium. The are a SH_TLOAD of wires back there!
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