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No retarder function.

June 21, 2018, 04:22:22 pm

Hopefully someone can provide some invite

We have a 1999 U 295.
Cummins 8.3.
Alison 3060md.

Our issue is this.

We have no retarder at all , factory tech  support has been less then stellar in both their response time as well as answers with regards to wiring , relay location etc. parts did provide diagrams of a generic type. We are perplexed.

Here goes.

Retarder switch and it's relay in front left relay fuse panel ,  seems to be getting ground to , and ground through as required. 12 volt signal seems to only run the light in switch. On post 87a however someone in the past has ran a wire from that post to a pressure switch under drivers floor  , with air lines going to it. And then connected to a unlabelled relay. 
I have worked on a lot of equipment. And this beast is the first machine that I have seen where virtually nothing is marked as to what it does. Lol

Transmission is showing no codes.

On a side note , and this may be key. Speedo is not working. Could this be the underlining issue. Has king throttle control. Cruise works to bring high idle up , but no cruise function.

We looking for any suggestions ideas or maybe someone's run into this before. Any help is always appreciated

Thanks.

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Re: No retarder function.

Reply #1 – June 21, 2018, 05:48:28 pm

Don't have a retarder, so no direct knowledge.  Found the online manual linked below - may or may not be helpful.  Skimming through the manual, I can see that there's a lot of things that have to work right for the retarder to function.  Good Luck!

http://ww2.justanswer.com/uploads/HE/HeavyEquipmentTech/2013-09-22_223029_allison_transmission_md3060_trouble-shooting.pdf

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Re: No retarder function.

Reply #2 – June 21, 2018, 06:35:51 pm

When speedo does not work as well as cruise, check ground both inside dash and then under coach at transmission.

Pierce

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Re: No retarder function.

Reply #3 – June 21, 2018, 07:46:14 pm

Retarder also does thru a relay in the ABS control box.

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Re: No retarder function.

Reply #4 – June 22, 2018, 12:14:59 am

Did retarder just stop working?  Has it been working ok for a long time?  How do you know retarder does not work?  Do you have joy stick? Retarder joy stick and the three air brake retarder pressure switches are connected together with a wiring harness that plugs together and then into Allison computer, so check these plugs.

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Re: No retarder function.

Reply #5 – June 22, 2018, 12:43:17 pm

Thank you for the replies.

The issue we are having is locating where any of these relays are. There is absolutely no labelling as to what's what. 
And advise where to look.

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Re: No retarder function.

Reply #6 – June 22, 2018, 02:35:11 pm

If you have the schematic, the wires should have a code on them. Problem is that the schematics don't show actual location of the components.

Pierce

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