Brake Light Circuit madness
#12
08-18-2015, 10:37 AM
This is a kraptastrophy! I got the new switch and put it in. Everything else was cleaned up and reconnected because I was way too confident in my diagnosis.
long story short - the fuse blows soon as I step on the brake. Back to square one with a brand new switch, I guess.
However, I dont know if I even have the right stuff to be doing this since my test light is not self powered, and I'm confused by my multimeter. Ive concluded there is a hot wire touching ground somewhere up front... but im not sure thats where it is, for sure. aaauughhh! Maybe if I scream I will at least feel better... not!
SO, I have a cent-tech 30 amp auto fuse circuit tester from harbour freight... but that isnt going to help... is it? What do I need to be using and how? ANybody....
long story short - the fuse blows soon as I step on the brake. Back to square one with a brand new switch, I guess.
However, I dont know if I even have the right stuff to be doing this since my test light is not self powered, and I'm confused by my multimeter. Ive concluded there is a hot wire touching ground somewhere up front... but im not sure thats where it is, for sure. aaauughhh! Maybe if I scream I will at least feel better... not!
SO, I have a cent-tech 30 amp auto fuse circuit tester from harbour freight... but that isnt going to help... is it? What do I need to be using and how? ANybody....
#13
08-19-2015, 09:22 AM
Test light doesn't have to be self powered, I use mine just for a quick check for voltage, then go to the meter set for DC Volts to check for 12v.
I use the Ohms setting for checking components for continuity and check wires for shorting to ground. (looks like a greek Omega symbol or an upside down u) If you disconnect all the bulbs, and check the wire going to the back end with the other test lead on a ground (set to Ohms) you should get an open reading (usually an OL reading) if you have any numbers or 0, you have a wire touching ground.
Measuring ohms across a disconnected switch, on the tabs on the switch, you should get a 0 reading (shorted) With the switch disconnected, all the bulbs removed, and checking the connection to the lights, (NOT the 12v power one) you should see a resistance, this is the trans shift unlock coil. Now go to the back of the truck, and make the same measurement on one of the light wires. One will be shorted (ground side) and the other should show the same value you got up at the brake switch wire (trans shift coil) if it is shorted, you got a pinched wire, a worn through wire. If the reading is higher, then you probably have a corroded wire or a corroded connector. .
That will take a lot of tracking down to find as it could be anywhere along the wiring harness from the back to the front.
Hope this helps You are on the right path anyhow.
I use the Ohms setting for checking components for continuity and check wires for shorting to ground. (looks like a greek Omega symbol or an upside down u) If you disconnect all the bulbs, and check the wire going to the back end with the other test lead on a ground (set to Ohms) you should get an open reading (usually an OL reading) if you have any numbers or 0, you have a wire touching ground.
Measuring ohms across a disconnected switch, on the tabs on the switch, you should get a 0 reading (shorted) With the switch disconnected, all the bulbs removed, and checking the connection to the lights, (NOT the 12v power one) you should see a resistance, this is the trans shift unlock coil. Now go to the back of the truck, and make the same measurement on one of the light wires. One will be shorted (ground side) and the other should show the same value you got up at the brake switch wire (trans shift coil) if it is shorted, you got a pinched wire, a worn through wire. If the reading is higher, then you probably have a corroded wire or a corroded connector. .
That will take a lot of tracking down to find as it could be anywhere along the wiring harness from the back to the front.
Hope this helps You are on the right path anyhow.
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