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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8417
Experience:  I am ASE Master Truck Certified.
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Jakes on sdp c15 model#sdp 05780 do not turn on gh,but stay

Customer Question

jakes on sdp c15 model#sdp 05780 do not turn on high,but stay on low
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.
Hi. Thanks for asking your question and requesting me! I will try and help you out.
Has the Jakes not worked correctly since the inframe?
Expert:  Cat Man replied 1 year ago.
The low brake is operated by sending power to the middle or 3 and 4 cylinder brake. The medium brake is operated by sending power to the front 1 and 2 brake and rear 5 and 6 brake. Since yours is only working on low, I would suspect a problem in the engine harness first. The front and rear brakes get power from pin 8 on the ECM and it sends it through the 12 pin connector pin 1.
You could also have a problem with the brake selector switch on the dash. But if this problem started after the inframe., I would suspect a harness problem.
Please reply back if you need more help or have more questions. I am happy to assist.
Expert:  Cat Man replied 1 year ago.
Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.

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