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Old 06-27-2017, 07:55 AM
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Tommycat Tommycat is offline
Join Date: Feb 2017
Location: North-western Illinois
Posts: 85
Default Bad fuse(s)...?

Originally Posted by tomkk View Post
Tomorrow I guess I'll go out and see if I can see some way to check intermediat voltages between the Control module that's at 9.7v to try to see where it drops to the 1.75v I see at the small yellow wire.

I don't understand the drop to 9.75v S & F module VREG output.
Cat troubleshooting rule #1...always start with the obvious. 9.75v is not right.

Follow electrical safety precautions.

Keeping your meter negative lead (common port) at the same grounding location. Probe to good metal contact with your meter positive lead (V positive port), meter selection on DCvolts.

Unit powered up, and connector disconnected...

Probe all three soldered on fuses, first at their power in lead. Then at their power out lead.

All 6 test points should read Battery voltage. (your 12.75v)

If it drops at all across the fuse, the fuse is bad. If the power in is low, the problem is further upstream. If they all check good, your problem is downstream.

Remember, a bad fuse is a result of a problem. Typically not the problem itself.


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