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Allison MD3060R neutral safety switch

June 17, 2019, 10:55:50 am

My '95 U-240 CAT 3116 with Allison MD3060R will not start(engage starter) until relay R1 on relay/wiring panel in front of the passenger seat clicks on and holds.  The relay R1 is labeled as Neutral Safety Switch.  The relay(R1) will start to chatter after a period of time(30-90 seconds) and finally click in and hold.  The engine will start then with no other problems.  I know that the relay is energized by a wire(purple) coming from the Allison ECU tranny(WTEC II) controller. 

First is it possible for the tranny(MR3060R) to be in gear(R/D) after the ignition has been in the off position and then returned to the on position and then start?

Second does the Allison MD3060R have a neutral safety switch in the tranny or is this just a function of the ECU?

I don't think there is a switch, I think this was for the lever operated gear selectors.  I think with the touch pad gear selector the R1 relay is a left over and not needed.  I think the ECU and tranny ensure the engine starts with the tranny in neutral.

Tell me what you think, am I wrong to do away with the relay(R1)?

Pat

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Re: Allison MD3060R neutral safety switch

Reply #1 – June 17, 2019, 05:53:24 pm

I had a related starting problem. With the help of an especially able Foretraveler, I finally figured out that, instead of battery voltage, I had 11.7 volts at the Allison ECU on wire number 123. That meant that the NSS relay was only getting 11.7 volts. Everything else checked out. I ended up bypassing the Neutral Safety Switch. In the central 12v wiring area behind the panel in from of the passenger seat, I jumped 122 and E9. this sends 12v back to the start relay in the back. The Allison always defaults to Neutral so it's not a safety issue. I would think your setup on the 95 would be very similar to mine. Good luck.
jor

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Re: Allison MD3060R neutral safety switch

Reply #2 – June 17, 2019, 07:06:35 pm

Since this relay is a common Bosch-type relay, have you first tried to swap it out? Could chatter be from Allison receiving a too low voltage from an up-stream source?

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Re: Allison MD3060R neutral safety switch

Reply #3 – June 18, 2019, 09:33:02 am

Thanks jor for the comment.  I agree with you,  but I will check the voltage to relay coil.

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