Fog light switch wiring
Submitted: Monday, Dec 08, 2008 at 23:48
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Member - Captain (WA)
I normally have no problems wiring things up, but this has got me stumped. I had
the spot light wiring done some time ago thru Toyota but I have only just gotten around to connecting it all up. I replaced the standard foglight switch (SPST - no indicator light) with one that has an indicator light (DPST - with indicator light, Navra 63027BL) and the whole setup works - except the indicator light doesn't come on (but have confirmed the light does actually work).
Now I didn't wire this myself, but what I can trace is that the
park light +ve wire is spliced into and runs thru the relay then on to the fog light switch with the switch return wire going back to the -ve wire of the
park lights (all makes sense so far to me!)
I now turn the fog lights on - they come on - but the indicator light doesn't, so out comes the trusty multimeter. With the
park lights on and the fog switch off, I have 12V to the fog light switch +ve terminal and confirm the switch light earth is also good, so far so good. I then switch the fog lights on (they come on!) but the indicator light is off. I check the +ve terminal again but now have 0V between it and earth...hmmm. Turn off the fog light switch, they go off, and now have 12V back at the switch +ve terminal. OK I give up and wonder what am I doing wrong... hopefully I cannot see the
forrest for the trees!!!
Cheers
Captain
Reply By: Thylacine - Tuesday, Dec 09, 2008 at 00:46
Tuesday, Dec 09, 2008 at 00:46
Toyo's use negative switching (ie constant power to load with the negative interrupted via switch).
ed
AnswerID:
338887
Follow Up By: Peter 2 - Tuesday, Dec 09, 2008 at 07:33
Tuesday, Dec 09, 2008 at 07:33
I've also come across light wiring on Toyota's that at rest have neither positive or negative at the light.
When you turn the light on it uses ground to activate a double relay which then switches both positive and negative to the light.
Some of the older Datsuns were wired the same.
FollowupID:
606419
Follow Up By: Peter 2 - Tuesday, Dec 09, 2008 at 07:37
Tuesday, Dec 09, 2008 at 07:37
Forgot to add too that some late model vehicles have just a common power wire running around the vehicle and it is switched on at each point by a microprocessor at the actual light.
I'd be very careful on the 200 as there have been a few disasters with people wiring up accessories like CB's and power sockets.
FollowupID:
606420
Follow Up By: Member - Captain (WA) - Tuesday, Dec 09, 2008 at 09:03
Tuesday, Dec 09, 2008 at 09:03
Hi Peter,
I initially thought the same thing myself but the wires have been spliced in right at the feed to the globe. Thus while the switching itself may be -ve, the actual power line to the globe is a simple two wire +/- feed (light housing is insulated).
I have wired up everything else in the 200 myself (DVD/GPS/radio, rev camera, air comp,
water pump, power outlets, UHF, trailer power, engels outlet, spot lights, mobile phone, etc...) and haven't had a problem. This is the only thing someone else did and only thing I am having trouble with. It certainly has me stumped.
Cheers
Captain
FollowupID:
606427
Reply By: Member - Captain (WA) - Tuesday, Dec 09, 2008 at 09:02
Tuesday, Dec 09, 2008 at 09:02
Hi Peter,
I initially thought the same thing myself but the wires have been spliced in right at the feed to the globe. Thus while the switching itself may be -ve, the actual power line to the globe is a simple two wire +/- feed (light housing is insulated).
I have wired up everything else in the 200 myself (DVD/GPS/radio, rev camera, air comp,
water pump, power outlets, UHF, trailer power, engels outlet, spot lights, mobile phone, etc...) and haven't had a problem. This is the only thing someone else did and only thing I am having trouble with. It certainly has me stumped.
Cheers
Captain
AnswerID:
338903
Reply By: Peter 2 - Tuesday, Dec 09, 2008 at 09:42
Tuesday, Dec 09, 2008 at 09:42
I wouldn't think that using the standard Tojo wiring to run foglights wouldn't be good, pretty light wire and possibly plenty of voltage drop.
I'd be wiring it all up myself.
Take the trigger from the low beam on the back of the headlight back through the original switch and then back to a relay which switches power to the foglights.
That way the fogs can only be used when on low beam.
If wiring spotties up then take the trigger from the high beam at the back of the headlight.
Of course this is all no good if it has HID's ;-))
AnswerID:
338909
Follow Up By: Member - Captain (WA) - Tuesday, Dec 09, 2008 at 10:50
Tuesday, Dec 09, 2008 at 10:50
Hi Peter,
There is a relay in the circuit, the wiring I am talking about is the solenoid part that pulls in the relay power. The fog lights are powered from a battery feed thru the relay. Also, I have taken the feed off the
park light circuit so that I can run the fog lights with the headlights off (I find this better in dusty/foggy conditions).
But the good news, I figured out (
well, an electrical engineer mate did) why its not working. The +ve wire goes thru the solenoid first (the load) then the switch. When you close the switch, there is no load thru the switch itself so it is effectively earth, hence why I got 0V when closed. All I have to do is move the wire to the switch before the relay (the load!) and not after. This will then mean the switch has a 12V potential and thus the switch light will work. So easy when you take a step back!!! (I hope I have explained it properly, a bit hard to describe but real easy in a circuit diagram).
Thanks for your reply.
Cheers
Captain
FollowupID:
606439