Lost tail lights and dash lights on my current trip. Any ideas? 2007 FG

[dtruzinski]

I am a week into a 2-3 week trip and just lost my tail and dash lights in my 2007 Fuso FG. I have disconnected the tail lights from the system and the minute I turn on the headlights, the 15 AMP tail light fuse in the High Current Fuse Box blows. So I thought maybe it is the rheostat, so I disconnected that and turned on the headlights...the fuse blows instantly. Something is clearly going to ground. Have other Fuso owners experienced this and do you have any recommendations to help isolate or troubleshoot.

Thanks in advance...
dave

 

[GR8ADV]

I assume that the 2007 is like my 2004 in that the headlights are on all the time. Turning the switch on activates the dash lights and tail lights which is likely causing the fail and not the headlights themselves. This is not an issue I would expect with factory wiring. I would begin with wiring you have done or disturbed. I would start with the tail lights and move fwd.

 

[calicamper]

Had a similar experience with a Subaru. After nearly tearing the whole car appart we found a bulb in a marker where the filament was tangled up and would short the fuse. Replaced the bulb and we were back in business. An idea to eye ball things worth a look. Hope it turns out to be a simple thing like that. Good luck

 

[Johnston]

Just a FYI for safety if some people don't know this. Your taillights and dash lights are on the same circuit on most every vehicle that way you know you don't have taillights if your dash lights are out.

 

[dtruzinski]

@Johnston - I learned this lesson the hard way. Tail lights and dash lights are connected on the FUSOs!

 

[dtruzinski]

@Calicamper - I disconnected the tail lights from the main circuit and the problem persisted...thanks for the comment though...others might benefit!

 

[gait]

this is either the ramblings of a deranged mind or some useful fault finding tricks.

my mental picture is of "control" wires and "power" wires. The control wires have switches and operate relays. The power is turned on at the relays.

Unfortunately some circuits are like that, others are just a single set of wires. Headlights, aircon / heater fan, headlights, electric windows, starter motor, etc have relays. Not sure what else.

Where that leads is the need to distinguish whether its a short to ground or to another circuit in a control circuit or a power circuit that's causing the fuse to blow.

Easier said than done of course. Once the obvious bits have been disconnected it can be a tedious case of continuity testing - is there a zero resistance where there shouldn't be. One trick is to find somewhere in a control circuit it can be disconnected, then, after much checking of circuit diagrams, apply power through a separate wire (bypass) and see what happens. If what is expected works the problem is upstream of the disconnect, otherwise downstream. And so on.

Given that its a high current fuse that is blowing its probably a power circuit and (stating the obvious) downstream of that disconnect.

Do you have a circuit diagram from manual? Its a tedious case of tracing wires and progressively disconnecting things.

So. After all the pre-amble. The high current 15A fuse B25 for tail lamps (in my FE/FG manual) supplies relay B19 (tail lamp relay) which when combination switch is on supplies normal fuses F2 and F3 (LH and RH tail lamps).

Which leads me to suggest removing fuses F2 and F3 then see if high current fuse B25 still blows.

And so on.

 

[dtruzinski]

@Gait...will try that in the AM...this condition is forcing me to quit driving at night and that's not all bad. More time to drink fine wine and eat while on extended walkabout of sorts.

 

[unkamonkey]

I'm afraid I can't help you. I was driving up to a friends cabin and hit some big holes in the road and lost my clearance lights, dash lights and radio. Screw it, I'm not going to play with this crap in the dark. A few miles later they all came back on. You may need to check for a relay somewhere or a circuit breaker.

 

[dtruzinski]

this is either the ramblings of a deranged mind or some useful fault finding tricks.

my mental picture is of "control" wires and "power" wires. The control wires have switches and operate relays. The power is turned on at the relays.

Unfortunately some circuits are like that, others are just a single set of wires. Headlights, aircon / heater fan, headlights, electric windows, starter motor, etc have relays. Not sure what else.

Where that leads is the need to distinguish whether its a short to ground or to another circuit in a control circuit or a power circuit that's causing the fuse to blow.

Easier said than done of course. Once the obvious bits have been disconnected it can be a tedious case of continuity testing - is there a zero resistance where there shouldn't be. One trick is to find somewhere in a control circuit it can be disconnected, then, after much checking of circuit diagrams, apply power through a separate wire (bypass) and see what happens. If what is expected works the problem is upstream of the disconnect, otherwise downstream. And so on.

Given that its a high current fuse that is blowing its probably a power circuit and (stating the obvious) downstream of that disconnect.

Do you have a circuit diagram from manual? Its a tedious case of tracing wires and progressively disconnecting things.

So. After all the pre-amble. The high current 15A fuse B25 for tail lamps (in my FE/FG manual) supplies relay B19 (tail lamp relay) which when combination switch is on supplies normal fuses F2 and F3 (LH and RH tail lamps).

Which leads me to suggest removing fuses F2 and F3 then see if high current fuse B25 still blows.

And so on.

Troubleshooting this is moving beyond my ability to read this electrical diagram. I am home now and have access to the 2007 repair manual. I have learned one more thing...this truck has a daytime running light (DRL) system. When the truck is started and the parking break is off, the headlights and tail lights are lit. Well on mine only the headlights light on the DRL system, but the tail lights are out. Every time I turn on the headlights the 15A fuse for the tail light circuit (located in the high current fuse box) blows. Any more ideas?

View attachment 313-DaytimeRunning Lights-1.pdf View attachment 313-DaytimeRunning Lights-2.pdf View attachment 320-TailCircuit.pdf View attachment FuseB25.pdf

 

[dtruzinski]

I assume that the 2007 is like my 2004 in that the headlights are on all the time. Turning the switch on activates the dash lights and tail lights which is likely causing the fail and not the headlights themselves. This is not an issue I would expect with factory wiring. I would begin with wiring you have done or disturbed. I would start with the tail lights and move fwd.

Good ideas...I disconnected all the wiring I disturbed, but I am the second owner and have begun a detailed search for any wire protection that does not appear to be factory.

 

[dtruzinski]

More clues: when my head lamps are in the off position and the truck is running (essentially on DRL system), still don't have tail lamps, but my 15A fuse does not blow. So I don't think the problem is in the DLR system, but I am at a loss to figure out where it is. I have torn the dash apart to get to various fuses and connectors. Still troubleshooting. Any ideas welcome. I am beginning to think it is the combination switch, but it is only a guess at this time.\\

 

[gait]

is there an electrical connection for a trailer?

But back to the difference between "control" circuit and "power" circuit.

The daylight stuff is just another way of turning the power circuit to the lights on. Just another way of switching the relay that supplies power to the lights.

Since its a power circuit fuse that blows the problem is probably between the relay that turns the tail lights on and the lights.

The manual has a diagram of the physical location of things like relays, switches and joints. The tail light relay has a number. Find the location and remove the relay. Then test again. After that follow the power wires from the relay. Disregard all the control wiring.

Removing the individual tail light fuses (if present) was another way of isolating another part of the power circuit.

 

[sprucemonster]

Did you figure this out? I have a 2007 and had the exact issue. I have a Morgan style box on the back. When i put in my ceiling in I must have shorted out the interior ceiling light. I solved the issue by disconnecting the interior light where it connects just outside of the fuse box. i have since removed the light.

page 41 of the FE_FG Part 1 body builders guide Fig. 6.5 shows the location of the Front van body interior lamp connector near the fuse box. There is also the connection for the tail lights at the exact same spot. I can't remember if you have a box mounted or not. hope that helps.

 

[dtruzinski]

@sprucemonster - yes I have a box, so I will investigate that connector. This is certainly a possibility

@Gait - thanks for the continued education and advise. I feel like I am hunting down a ghost. The tail light relay is in the high current fuse box. As I understand the diagram, power comes from the batt comes to the fuse (B25), crosses the fuse and hits the relay (U12). When I remove the relay and turn on the lights, nothing happens, but that's to be expected as there is no power source. I just noticed that one of the leads heads to Van Body Dome (assume this is what spruce monster was mentioning)...warming up for a few and back at it.