Volt Drop

[Jason2tpa]

1998 S115TLRW


Went to install new fuel gauge powered by middle yellow pigtail in the tach harness. Gauge didn't power up. Removed the gauge from the tach harness circuit and hooked up power/ground to terminal block. Gauge works. This led me to volt drop test the tach harness yellow pigtails...getting 11.6v.

Moved further back testing the red wire in the 10pin engine harness...getting 11.6v. Moved further back to engine battery terminals...getting 12.7v. But here's the strange part, or at least to me.....the tach powers on and operates normally, oil reservoir pump operates normally, and no engine cranking issues. The tach is grounded via the tach harness via the 10pin harness, right? How is the tach working on less than 12v? And where do you suggest I next volt drop test to locate the issue?

Btw...the tach you see below is not the model I have...mine does not have the 2 push buttons and does not utilize the red pigtails



Ignition:Throttle:Tach copy.jpg

[99yam40]

look to see what the red wire to the key switch is,
that is what feeds to the yellow wire leaving the key switch
could be the key switch, just need to find out where the voltage is dropping off at

[Jason2tpa]

look to see what the red wire to the key switch is,
that is what feeds to the yellow wire leaving the key switch
could be the key switch, just need to find out where the voltage is dropping off at

I bypassed the ignition switch by testing the power its receiving from the red 10 pin harness....11.6v...and then I tested tach harness yellow...11.6v.

[99yam40]

I bypassed the ignition switch by testing the power its receiving from the red 10 pin harness....11.6v...and then I tested tach harness yellow...11.6v.

follow the 11.6 back towards the battery until you find it go back up

[Jason2tpa]

follow the 11.6 back towards the battery until you find it go back up

Will do. Can you take a stab at how the tach is functioning on 11.6v??....that’s what really has me puzzled.

[99yam40]

not all equipment has the same shut down voltage,
anyway that is all I can come up with

[fairdeal]

The battery "+" connects to the starter relay,
and from there,
through a fuse
(inside a black rubber capsule)
to the red wire of the 10 pin harness -
and then directly to the helm.

Separate the harness connector at the engine -
what voltage do you have there on the red pin of the engine side?
if that's not the same as the battery voltage,
check the fuseholder

[Jason2tpa]

Thanks Fairdeal, will do!