Failed enabling both Analog & Digital Gauges

[MtlBen]

Since both fuel and temp gauges are grounded via the instrument cluster, I had a theory that the cluster would sense the ground return current to determine if any of the analog gauges were connected.

I disconnected the ground wires from both gauges and jumpered the instrument grounds back to the jump-start ground connector, bypassing the instrument cluster.

When I turned the switch back to ON position, both analog gauges worked fine, but no digital gauge in the cluster. I did verify my connections a few times before and after the test...

The cluster is using a different mean of sensing the presence of the gauges. :dontknow:

...Just in case you had the urge to test this yourself...

...Ben...

 

[NancysToy]

Thanks for volunteering as our Guinea Pig.

 

[SpyderFun]

Output Power Source

Providing direct power won't work on any instrument gage where a needle measures a range (ie hi volts = full/hi whereas low volts = empty/low).

You need to supply "power from the output source". This would require a "Y" lead going from the "output" to 2-different "inputs". But doing that may throw a code due to the BUDS possibly sensing additional voltage drop.

 

[MtlBen]

Providing direct power won't work on any instrument gage where a needle measures a range (ie hi volts = full/hi whereas low volts = empty/low).

You need to supply "power from the output source". This would require a "Y" lead going from the "output" to 2-different "inputs". But doing that may throw a code due to the BUDS possibly sensing additional voltage drop.

Looking at the wiring diagram, both the cluster and the gauge receive the same fuel level signal from the fuel pump module. The temp gauge seems to receive its temp signal from the cluster itself. Providing a separate ground as I did should not affect operation. Actually it did not change anything. The odd part is that each gauge receives 2 separate power inputs, but both power inputs seem to be connected at the same source. Probably one power for lighting and one for signal measurment, but still odd.

After re-reading the shop manual, I found something on page 484 about cluster canbus communication, but it is unclear if it actually communicates with the fuel gauge over the canbus network:

"... Reads the low fuel level of the optionnal analog fuel gauge."

I have not given up yet.

...Ben...

 

[MtlBen]

:clap:
Actually I thought the very same thing, thanks for testing it out.

They must current sense the gauges in the V+ circuit.

I do not beleive so: there are no intelligent modules I could see between the battery and the gauge power input.

My best bet at this point is a communication handshake between the cluster and the fuel gauge over canbus.

...Ben...