[BLOWNBBC2]

I am having a strange issue. The ign terminal at fuse box, where i am triggering my holley ecu off, is getting 5v when key is in acc position. I am also getting a 5v reading at the oil psi and temp sender wires (dummy light dash) when in acc position, and 5v at the pink wire from ignition switch plug. If i remove the "gauge" fuse, i no longer get 5v at the ign terminal when in acc position.

Any ideas what could be backfeeding into the ignition circuit when in accessory mode? Id like to be able to play the radio in accessory mode, however its causing my ecu to turn on since its seeing voltage.

 

[Jim Streib]

What year and model vehicle and then what type of fuse block (factory or aftermarket or ?????)

If the fuse block is stock, is anything plugged into the "tap" as I call them next to a particular fuse that has an added electrical device plugged into it (such as a cruise control, rear defroster, etc.).

The terminals I refer to as "taps":

If there is anything aftermarket wired to the car, maybe try unplugging all of that stuff and slowly plugging them back in one at a time until the issue arises and then unplug that device and try the remaining ones. You may have one or more issues.

Double check your grounds also ?,

Maybe a device that was added has a diode that went out allowing a backfeed condition ?.

Jim

 

[DUTCH MAX HEADWORK]

Disconnect your alternator plug and see if you still get the 5 volts to the ignition. If so, one of your diodes may be tanking in the alt. If it goes away, do an a/c ripple test on the alt output and you'll find excessive a/c in the output.

If you have an aftermarket ignition box, unplug it and test your voltage.

Both hail Mary's but worth a 5 minute test.

Disconnect your ECU because it could cause this. Many use 5 volts or about for their sensors.

You can start pulling fuses, particularly those on the right side of the fuse box as those lead to the ignition switch for power. You're just trying to isolate the circuit so you can further test that circuit once you find a clue.