GU1 Sub Tank Switch

[Yendor]

Ok so...

Terminals 1 and 2 act as they are supposed to.

#1 is showing around 5.04v until the button is depressed, then down to zero.

Pin #3 has around 500mv.

Pin #4 is where my issues start, I do not have any voltage and grounding it does not illuminate the light on the switch.

I have just bought a new multimeter from Jaycar and it has some strange induction thing that i don't understand so my 500mv may have been a false reading of zero. The car has gone to the movies now with the missus as I am about to leave for night shift, so re-testing will have to be done tomorrow.

Could a faulty light lead to a zero reading? Could this lead to the diagnoses mode not activating correctly?

Was the ignition turned on? Was it a White wire with a Black trace that only had 500mv?. If so, check fuse 28 in the fuse box inside the vehicle. Make sure it isn't blown or have a bad connection.

500mv is not enough to power the light. It should be 12 volts.

[NotTortoise]

OK, my bad on the 500mv, I don't know what I did but that wire has 12.55v with the ignition on.

However pins 3 and 4 do not show any continuity on my meter whether the switch is activated or not.
-Is this a test that I should do with the switch plugged in? (I have been doing all of my tests on either the harness or switch when I have had them disconnected.)

-If it is a faulty light, is there a way to repair it?
-Would this maybe be enough for the self diagnostic mode to not activate?
-Is a light fault enough to trigger a sub tank fault light in the dash?
-When the dash light gets activated does it suspend the system from attempting to work?

The car is in Brisbane until next Wednesday so I might order a new switch tomorrow in the hope that that will fix it.

Sorry for all the questions, but you guys are geniuses, a whole heap more helpful than the bloke I had look at it in Isa he told us that "it is what it is, carry jerry cans"

Thanks for the help

[the evil twin]

Yes, if the "sub tank" fault light is illuminated the system will not work
Even after you fix the fault that caused the computer to set the "sub tank" light to reset that fault light you still have to either disconnect the battery, pull about 3 fuses or unplug the sub tank computer (battery is usually easiest).

I haven't ever pulled a sub tank switch part so don't know if it can be done and/or the globe replaced, Rodney (or someone else) may know.

When you get a chance can you also confirm both your fuel gauges are working OK and whether the "sub Tank" fault light is on or off

[NotTortoise]

Dash light is illuminated and both gauges are fully functional

[the evil twin]

Dash light is illuminated and both gauges are fully functional

OK, that means each time you "fix" something you will need to disconnect the battery to see if that was indeed the fault and reset the fault codes.

IIRC an open cct in the switch tell tale globe (that tells you the pump is running) will cause a "sub tank" fault but I am not 100% on that

[Yendor]

12.55v on pin 3 is good. If you earth pin 4 and the light doesn't come on (switch plugged in) light in switch is stuffed.

I haven't pulled a switch apart, not sure if you can replace the bulb.

Someone on here told me that a workshop was replacing switches all the time. Now I can't see the contacts in the switch causing problems (between pin 1 and 2) but it could possible be a blown bulb in the switch that might be causing the issue.

When the "Sub tank" light is on in the dash the system will not work.

Have you tried disconnecting the battery and then try to access self diagnostic mode?

[NotTortoise]

In self diagnostic mode is it the dash light or the button light that blinks the fault codes?

[NotTortoise]

Sorry, what is IIRC?

[the evil twin]

Button light... so if it is blown obviously you cannot read the codes unless you put another bulb across the terminals.

[NotTortoise]

I will try the battery disconnect fix before trying diagnostic mode tomorrow. I don't think I tried that after i tried the battery. I just saw the light still on and went bavk inside to mope around