My dad has a 98 12v with a cummins e brake made by jacobs witch the part numbers are ( jacobs 022453) ( cummins 3933128) and it is not working, seems to be electrical. It has 2 inline fuses one for the main power just off the fuse box and one off the switch and whet the truck is off and you hit the switch it activates the relay but doesn't actuate the brake. but when you fire the truck up and hit the switch both 20a fuses blow. if anyone has any ideas it would be very helpful also if you have the same system and you have installation instructions or operating instructions I would love to see them.


this is a exhaust brake like a BD

 

sounds like a grounding problem to me. have you checked all your wires for chafe threw were it may be contacting a grounding surface?

 

All of the grounds are good

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Ill check the wires next time I'm there it look easy enough to pull the harness off since it all covered with weather guard