Is this a short?

[MuddFlapp]

When I check resistance from the trailer running lights to the ground with no power, the ohm meter shows 1.3 and I get the audible buzzer. Does that constitute a short? Even though I'm not blowing any fuses

Thanks.

 

[phantomusa]

Any time you go to ground your shorting the system out ?????

 

[Tuesdak]

I'd guess "No short" due to lack of knowing what problem you are chasing. Looks like you are testing the resistance of the running lights... Every "cold" bulb in the circuit will have low resistance and this is what you are measuring. As the filament heats up from cold the resistance goes up. A short would have no running lights lighting up and likely pop a fuse. (I have seen high resistance shorts not pop a fuse.) Perhaps test the trailer running lights by applying 12v through a 30a breaker from a battery.

 

[Wayne M.]

I'd guess "No short" due to lack of knowing what problem you are chasing. Looks like you are testing the resistance of the running lights... Every "cold" bulb in the circuit will have low resistance and this is what you are measuring. As the filament heats up from cold the resistance goes up. A short would have no running lights lighting up and likely pop a fuse. (I have seen high resistance shorts not pop a fuse.) Perhaps test the trailer running lights by applying 12v through a 30a breaker from a battery.

Well explained. Muddflap, what are you chasing?

 

[MuddFlapp]

Well explained. Muddflap, what are you chasing?

It started out a breaker in the trailer light breaker box Motorhead was building for awhile was tripping when I turned on the running lights. So while chasing that (which turned out to be a bad breaker), I was testing continuity between the running light wire and ground and found there was a connection, (the beeping of my multimeter), which seems to me to be a dead short.

That being said since I replaced the breaker in the box, everything works as it should. I was just concerned because it appears that I have a connection between the running light wire and ground with no power to the system. I'm not a rocket scientist so, by all means, I could be misinterpreting what I'm seeing.

Thanks for the help.

 

[phantomusa]

As long as everything is workin dont try to over think theres a problem

 

[MuddFlapp]

As long as everything is workin dont try to over think theres a problem

Yeah, probably not even a problem there.

 

[Tuesdak]

You are just seeing the circuit that all the light bulbs have to ground. The low resistance of a cold filament is making the meter beep. Try it out on just a single spare light bulb and you should get a "beep" across it. IF you ever do have an issue you would have to remove each and every light bulb on the trailer and then you should get an open - this is simply not done. Intermittent shorts are common and why we use breakers, not fuses, for trailer lights. So you would get the running lights shutting off when the rubbed through wire shorted and the next bump the breaker resets and the short is gone. No fun to track down. More or less follow the wires and inspect for rubbing where they go through holes in the frame than in each fixture. IMO you fixed the problem with a bad breaker.

 

[MuddFlapp]

I get it, the light bulb just came on.:-laf

Thanks one and all for helping me understand.

 

[Wayne M.]

What you're experiencing is how the FCM/ TIPM knows there's a lamp out. It watches circuits kinda like you were, and when the "beep" goes away (open circuit) it dings the chime and lights the warning.

 

[Gumby79]

+1 on the bulbs are connected to ground. A short would be 0 ohms.
GE calls out .9ohms for a 1157

 

[Motorhead]

It started out a breaker in the trailer light breaker box Motorhead was building for awhile was tripping when I turned on the running lights. So while chasing that (which turned out to be a bad breaker), I was testing continuity between the running light wire and ground and found there was a connection, (the beeping of my multimeter), which seems to me to be a dead short.

That being said since I replaced the breaker in the box, everything works as it should. I was just concerned because it appears that I have a connection between the running light wire and ground with no power to the system. I'm not a rocket scientist so, by all means, I could be misinterpreting what I'm seeing.

Thanks for the help.

MuddFlapp, Since I built and sold those TIPM Savers, Yours is the first failure on one circuit. I still have the prototype running in my '07, 5.9. I have a suggestion... If you have a way to check the TOTAL RUNNING light load with an Ammeter, that would tell a lot. I can't remember whether I put 15 amp or 20 amp thermal reset breakers. I thought I put 15 amp in. Anyhow, Try to put the meter in series with the trailer running lights. You could re-open the TIPM saver, REMOVE the breaker for the running lights. Make up TWO wire leads with each one having a 1/4" MALE push on connector and install them into the breaker socket, one in each female receptacle. Hook the ammeter up to each wire and with the trailer plugged into the truck, turn the lights on and read your total amp load for the running lights. Are you running LED or TUNGSTEN lights? PM me next time if you have a problem and I will be happy to help you. Chris

 

[dfb]

In order to save on wiring, YHE entire chassis is the negative or ground. Your meter is showing continuity between positive side of YHE wiring to the chassis. That's what you want. A short would blow a fuse. This would be continuity BEFORE the bulb.. bad juju... in other words the circuit is completed SHORT of where intended..