something odd...electrical hickup.

[Ambulancechser]

had a floodlamp go out on my m-1010.it's the passengeer side one,on the ambulance body.thinking it's a simple burnt out bulb...so i remove the entire flood assembly and test for continuity with my multimter.surprised to find that the bulb is good.

now i think that i have a bad ground,as these floods are the one wire type,that ground through the mount.back to the ladder,and test the mounting point for power.black probe to body,red to power wire...surprise...12.40 volts.

now i remount the assembly,and leave the power wire dissconnected.test for continuity between mounting foot and ambulance body (to see if i have a decent ground path)...good continuity.

now go to the drivers side flood and repeat the above...that side lights up fine,and also reads 12.40 volts.remounted that side and left it alone.it works .

went back to passenger flood,removed and installed a new flood (previously tested,it works same as first)...no good.remove assembly and test voltage.still 12.40 volts.

Now i'm confused...the floods (i actually tried 4 in total) refuse to work on the passenger side flood mount.i get voltage at that point,but don't seem to be getting current.this is interesting...iv'e never run into this before.i checked the t'm's for the service light digram,and found it to be a rather simple circut.nothing jumps out at me.

any thoughts?any other tests to run?

 

[papercu]

help

Bad plug? Did you remove just the bulb and check voltage at the wires? If the assembly grounds thru the frame and the mount rotates it may lose ground there.Wayne

 

[WillWagner]

RE: help

Maybe a broken wire with only one strand...unable to transfer amperage? Or a bad ground.

 

[Militoy]

RE: help

Testing for voltage with a DVM (or even a good analog meter) won't necessarily spot a loose or corroded connection. The voltmeter draws only microamps - so it will show voltage if there is any connection at all - no matter how poor - as long as the circuit is unloaded. My guess is that you likely have a loose or corroded connection, or a loose ground. You might try connecting a smallish bulb of the appropriate voltage across your meter probes while you are measuring the voltage, to provide a little load. A poor connection should show up with a lower measured voltage, and maybe a dim output from the test bulb.

 

[cranetruck]

RE: help

Good explanation Militoy, sometimes a test light works better than a VOM (DVM)....

 

[Ambulancechser]

TEST LIGHT...

Test light...makes sense to put a load on it.i don't have one,so i'll pick one up tonight.
what,potentially,could cause this?it certainly seems like a bad ground...is there anything else i should look for...pehaps a bad switch?

 

[cranetruck]

RE: TEST LIGHT...

Bad ground, bad ground, bad ground, bad ground, bad ground, bad ground bad ground, bad ground, bad ground, bad ground, bad ground bad ground, bad ground, bad ground, bad ground, bad ground bad ground, bad ground, bad ground, bad ground, bad ground bad ground, bad ground, bad ground, bad ground, bad ground .........

 

[73m819]

RE: TEST LIGHT...

bjron, do you think it might be a bad ground???????

 

[cranetruck]

RE: TEST LIGHT...

Did I give that impression?

 

[Ambulancechser]

KAY...

i take it you have some experience with bad grounds...
i agree by the way.it's a classic ground problem.

problem being...the other flood works fine.they both ground to the same body section,that being the ambulance box.so...box to frame ground path is fine,frame to electrical is fine.threads on bad flood mount are clean.going to install the flood on the bad side and check ground from the light to the body.

what would happen if i had a short in the power wire to the body,active only when the switch is thrown, aside from a spark or two?(just thinking)

Our work day has been cancelled due to high winds,so i can go get that test light.and some more paint...color change in progress.
thanks for the tips.

 

[rmgill]

RE: KAY...

Make sure the contacts in the bulb housing are good too. Make sure the houseing for the bulb has a good solid ground as well where it goes from the shield on the bulb fitting to the bowl to the mounts and to the ground. IF it comes apart with bolts/nuts, add some star washers to make the ground work better.

 

[Jones]

RE: KAY...

A short in a power wire substantial enough to keep a lamp from working would probably trip whatever circuit protection there is... is the fuse/circuit breaker good; or the switch itself? I know these may sound like dumb questions but often the problem is one you'd never think to check 'cause "it couldn't possibly be that..."
Wires do break or get pinched inside the insulation occasionally so running jumpers is a good test. Jumper battery to lamp switch,then lamp switch (both through and around switch) to lamp, then lamp to ground. That should show which leg may be bad.

 

[Blood_of_Tyrants]

Re: RE: help

Maybe a broken wire with only one strand...unable to transfer amperage? Or a bad ground.

Or broken but touching. I have had that problem before.