Switching off overdrive - momentary zero voltage

[Steve Hiatt]

I have a GKN gearnob and switch, wired directly to the o/d solenoid and I've noticed when I disengage it the digital voltmeter on my dash momentarily drops to zero. It's the same even if I unplug the solenoid. No other switches seem to cause this and it doesn't seem to cause a problem other than worrying me. Any ideas?

[errol209]

I have a GKN gearnob and switch, wired directly to the o/d solenoid and I've noticed when I disengage it the digital voltmeter on my dash momentarily drops to zero. It's the same even if I unplug the solenoid. No other switches seem to cause this and it doesn't seem to cause a problem other than worrying me. Any ideas?

Where is the voltmeter wired to exactly?

[western]

Standard connection for a voltmeter is one of the White ignition controlled wires behimd the dash, I've never seen my voltmeter drop when my GKN is switched out, reckon yours is using a common feed somewhere

[Steve Hiatt]

I'll have to refresh my memory on the wiring, but it is likely that the O/D and voltmeter share a common feed or earth.

Thinking about it there may be a relay, I switch the solenoid directly, not via a control box.

[errol209]

Standard connection for a boltmeter is one of the White ignition controlled wires behimd the dash, I've never seen my voltmeter drop when my GKN is switched out, reckon yours is using a common feed somewhere

Yep, my thought exactly, plus the possibility of a dodgy earth.

Edit: it could be that the meter is going out of range (too high) on a spike, or to zero.