[Shop-talk] Finding a Blown Fuse (Automotive)

[eric at megageek.com]

Eric,   There are devices (sometimes called 'tone generators' or similar) 
that are two parts.  One piece you put on the wire, the other creates an 
audible tone as it gets anywhere close to the wire.  You can use this as a 
means to follow the wire.

One other possibility... is it possible that another bulb is burnt out and 
that is acting as a fuse?  Maybe all the fuses are good?  Do you have a 
multimeter to check the wiring?

Just some thoughts.

Moose



From:   Eric Russell <ejrussell61 at gmail.com>
To:     Shop Talk <shop-talk at autox.team.net>
Date:   11/10/2021 19:18
Subject:        [Shop-talk] Finding a Blown Fuse (Automotive)
Sent by:        "Shop-talk" <shop-talk-bounces at autox.team.net>



Oh wise & beneficent Shop Talkers - I've run into a situation that has me 
stymied. I need help locating a blown fuse in a motorhome. 

We recently bought a new (to us) motorhome. When installing the signal 
booster for a TPMS (Tire Pressure Monitoring System) I 
accidentally shorted a 12V wire in the cargo bay lights. There was a small 
spark (followed by a few swear words). I then went on a hunt for the blown 
fuse. There are three fuse panels in this motorhome. Two in the Ford 
chassis (F-53) - one under the hood and the other inside near the parking 
brake - plus one in the motorhome's 120V - 12V power converter. I could 
not find a blown fuse anywhere. 

I contacted the manufacturer (Thor) who has actually been quite responsive 
& has tried to help. After asking for my vehicle's VIN they emailed me 
some schematics (not actual wire diagrams but more a map showing the 
general location of outlets, switches, etc with indications of which 
circuit they belong to). There are two schematics that appear to apply to 
my motorhome - one indicates the cargo lights are connected to the Ford 
panel by the parking brake, another indicates they are in circuit #6 of 
the converter's 12V panel. Neither of those fuses are blown. While there I 
checked all the fuses I could locate - none were blown. I've also signed 
up to a couple of motorhome forums but have not been able to find an 
answer there. 

Finally - my plea for help - is there any device one can use to trace 
where a circuit originates? I've seen an electrician use a device to find 
out what outlet goes to which breaker in our house.

I've followed the hot wire from the cargo bay light back to where it 
enters a wire harness along the motorhome's frame rail. I'm loath to rip 
open the wire harness trying to chase the wire further upstream. As far as 
I can tell there is nothing else in this circuit - everything else is 
working properly. Of course I can live without cargo bay lights but it 
bothers my OCD to have it not working (when I know it did before my screw 
up). 

-- 
Eric Russell
Mebane, NC_______________________________________________

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