No hazard voltage

[waltmgb]

Finishing up a rebuild where dash was removed/replaced but no new wiring done. Switched to LED signal bulbs and purchased the electronic flashers for signals and flasher. Neither now work. Wiring diagram shows brown wire from starter relay through fuse to hazard flasher. There is 12V at the brown wire at the relay but not at the flasher. I cannot find any fuse in what appears to be both ends of that brown wire. Wire runs into harness and through firewall. Where might the fuse be?

[Vic Butler]

What year is the car?

[waltmgb]

77 MGB, built 25 May 77.

[Vic Butler]

I'll have a look at the wiring diagram and report back.

[Vic Butler]

I've checked the wiring diagram in my manual and the main feed from the fuse to the direction indicator switch is a purple wire. At the fuse there's a brown wire from the ignition relay going into the fuse and 2 purple wires coming out. 1 purple wire goes to the cigarette lighter and the other to the indicator switch. From the switch a light green/brown trace wire goes to the flasher unit and a green wire from there goes to the hazard warning switch.
On my October 1977 built MGB GT the fuse is the bottom one. It's the only one in the circuit so worth checking it hasn't blown.
Hope this helps.

[waltmgb]

That is vastly different from my wiring diagrams. Two brown wires come off the starter relay terminal C1. One to the starter solenoid and one to a fuse. Other side of fuse is brown wire directly to the hazard flasher. All wires from there are some combination of g/lg/w/r for both hazards and turn signals. The part I can't find is the location of the fuse. Found the relay end and the flasher end. 12V at relay, nothing at flasher. Wire has no continuity checking with ohmmeter. Probably blown fuse but I can't find it. Relay end goes directly into wire loom and hazard end comes directly out to flasher. Really confused as to fuse location.

[Vic Butler]

I' m using the 1977 wiring diagram in the official MGB Operations Manual and the fuse box on mine is vertical and the relevant fuse is the bottom one.
I wonder if your MG is the earlier rubber bumper one. Does it have dual circuit brakes and 2 relays in front of the fusebox? If not, I do have a wiring diagram for it but the manual is out on loan at the moment (which reminds me I must get it back).

[waltmgb]

I really appreciate your time and research, Vic, but your wiring diagram doesn't match the colors in my car. I'm using both "The Complete Official MGB 1975-1980" by Robert Bentley and the diagram(s) from Auto-Wire and they both match my wire colors and connections. If I did it right a picture of the fuses and relays is attached. Still can't find that darn fuse.

[Vic Butler]

That's completely different from my MGB fuse layout. Yours is the earlier rubber bumper version then. I can see the main feed brown wire you mention. Is that fuse ok?
I'll try and get my other manual back and have a look at the diagram in it asap.
I think from memory the changeover was around July/August 1977 to the latest spec rubber bumper B's.
I've found it's easier to work backwards on wiring diagrams. Start at the hazard switch and work backwards until you reach the main fuse block. That's how I do it.

[Michael Barclay]

Hi Walt
There are two flasher units that operate the indicators. One operates the normal flasher /indicator operation and one operates when the hazard switch is operated. The standard flasher can be identified by the Green /light green wires going to it. The hazard flasher has the fuse and brown wire you mention connected to it. This should not affect normal flasher operation. The 12v feed to the standard flasher unit (Green wire) comes from the heater motor switch via the hazard switch. Try operating the hazard switch a couple of times as it could be poor switch contacts due to not being used for some time. Next check for 12V on the green wire connected to the standard flasher unit. (Ignition on) You could also try connecting 12 v directly to the flasher unit and checking the indicator operation. If still no go then it can only be an issue with the new flasher unit, indicator switch or LED bulbs. (They are polarity sensitive)
Hope this helps.
Mike