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Allison retarder intermittant operation

November 24, 2020, 10:22:16 am

Sometimes the retarder works, sometimes not. It started a while back, maybe a year or so. With the switch on, no light or felt response when activating the rocker or brake pedal. I could shut off the engine and when started back up (such as stopping in a rest area) it would usually work again. Maybe for days. The problem progressively got more frequent and the restarting trick wouldn't work. I have checked connections behind the dash and all seem clean and tight. I was hoping that fixing the ABS problem with the defective right front sensor would solve the problem. I know that there is a relay in the ABS control box associated with the retarder operation. The ABS warning indicator is no longer illuminated but the retarder still isn't working.

Haven't found much using the search that indicated anyone else having a similar problem. Thought I would throw this out and fish for suggestions. 🎣

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Re: Allison retarder intermittant operation

Reply #1 – November 24, 2020, 11:36:05 am

Justin,

Have you checked the wiring at the accumulator tank for a bad connector or a frayed wire?
Does your coach have the retarder rheostat or just the 3 stage off the brake?
Have you checked the ground where the retarder control box is grounded to the frame under the dash?

Mike

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Re: Allison retarder intermittant operation

Reply #2 – November 24, 2020, 12:30:20 pm

Mike
1) only visual, have not removed and checked plug but I will later today. Didn't think that would cause the problem (no indicating light) but I certainly will check it more thourghly. 

2) I have the joystick upgrade.

3) I had checked that this summer when we had the (no power to keypad issue) I'll check grounds again. 


Thanks

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Re: Allison retarder intermittant operation

Reply #3 – November 24, 2020, 12:50:32 pm

I missed the part that your indicator light wasn't working.  Now that leads to the relay that controls that hole mess. I don't know exactly where yours is located being a GV. I generally wouldn't recommend throwing parts at a problem but those relays are pretty cheep. You may have a relay that is failing and changing it out is worth a try. If you want to you could pull the relay that controls the docking lights and do a swap out.  If the dock lights start not working properly and the retarder works than you sure found the trouble.

Mike

On the Unicoaches it is hid behind the kick panel just in front of the passengers seat.  With your coach being made during the swap over body style yours could be hid under the dash. I don't get many '95 GV through here but they didn't make that many anyway so location will be a seek mission.

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Re: Allison retarder intermittant operation

Reply #4 – November 24, 2020, 08:59:48 pm

Thanks for that info Mike, I'll look for the relay tomorrow.
I think I have a spare relay for the dash vacuum pump, probably the same 5 pin relay.

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