Someone please help me, before I pull out the rest of my hair! Have a 99 f350 7.3. I picked this truck up used a couple weeks ago. While fixing the nightmare headlights someone butchered up in this truck, I thought I’d attempt to fix the turn signal on the front driver side, as it don’t work. All the other turn signals work, flashers all work accept for this one. I’ve replaced the bulb, replaced the socket, checked fuses and relays. Even cut off the old connector from the wiring harness (That plugs into the socket) and attached one that I know works. Still nothing. While grounded, I can connect both wires, one at a time (labeled minor and major on the new socket) and connect them to a hot source. Each wire will light up a dif filament on the turn signal bulb. When the lights are on, the bulb lights up as a running light as it should. It just won’t flash. I’m not sure if this matters or not, but the arrow on the dash don’t light up either... anyone have any ideas on where to go next?

it may be worth mentioning that I don’t know crap about electrical on vehicles. I don’t have a test light or anything of that nature.

thanks.

 

This is the new socket. I’ve figured out that the wire labeled minor (brown wire) is the running light. When the headlights are on, or I connect this wire to the hot battery wire, one filament on the turn bulb lights up, as well as the running light.

Wire labeled minor to pos battery cable. Running lights on.

This is with the wire labeled major, turn signal wire (green with white chaser line) hooked to the positive cable. Turn filament lights up.

With the headlights on. Running lights work. With the headlights off, and just the flashers/turn signal on, nothing on the front driver side flashes.

 

So you have verified that the socket and wires from the socket are good by connecting to the battery, and there is voltage for the parking light arriving at the socket but there is no voltage for the turn signal side arriving at the socket as it only works when you jumper it directly to the battery. Am I correct so far? If so it might be that there is either an open wire from the multifunction switch or the multifunction switch itself is bad.

 

The things that come to mind, the arrow doesn’t work so the socket doesn’t work. Pull the gauge cluster and replace the bulb behind the arrow.
‘The multifunction switch is bad. These are just guesses...


Multi function switch: Turn Signal Switch compatible with Ford F-Series Pickup 97-00

 

Bigb56: yes, you are correct so far.

colorado350: are you saying, that if the turn signal light in the gauge cluster don’t light up, then this could possibly cause the socket at the front turn lamp to not work?

my next step was to pull the cluster and see what I might find back there. You guys mentioned a malfunction switch? Where would I locate this? All the other turn signals work accept for the front driver side... I have looked over the wiring harness, and everything seems to be in order. No spots rubbed through, nothing seems like it’s been hot. I hate electrical gremlins.

ill take all the guesses I can get. Eventually one will be right haha!

 

The multifunction switch is the turn signal switch that Colorado linked in his post. Each turn signal passes through this switch individually.

 

My bad I didn’t even see the link. I will check it out. Thanks!

 

No, it doesn't work like that. But it looks like the guage indicator is on a parralell circuit with the front turn lamp. So, if both are inop then it's probably upstream of there, probably in the multifunction switch (turn signal switch).

Try this....

Apply 12v power to the 'major' wire and see if the guage indicator lights up. If it does, the wiring from the turn signal to the multifunction switch and then to the guage cluster should be good.

I had a hard time figuring out exactly how the multifunction switch works by the diagram, but I think if all other lights work and the above test illuminates the guage indicator, that pretty much confirms that the multifunction switch is bad.

 

Kbeefy, I didn’t figure it worked like that... but I wasn’t entirely sure either. I will try what you suggested. I didn’t think to look, and see if the indicator light came on when I was working on it earlier. The previous owner has this truck a mess. I did make a homemade probe. Hooked a small gauge jumper wire to a sewing needle. Hooked the jumper wire to the turn lamp wire and stuck the needle in the wire as far back as I could track it in the engine bay with no avail. The jumper probe worked, I tested it on the battery first. So I’m betting the switch is the culprit. Well.. praying the switch is the culprit. I’ll report back tomorrow if the indicator light comes on when hiking it to a power source.

 

Sounds like your on the right track... and made your own test lamp!

Once you grasp the concepts 12v DC is pretty simple. It's just figuring out whats happening inside the black boxes that can become confusing.

 

Kbeefy, I had a chance to hook up my jump wire to the major wire this afternoon. The turn signal indicator does indeed light up when it’s connected to the positive post of the battery. Meaning the bulb in the cluster is good. I’m gonna order a new switch and install it. Hopefully that cures my issue.

thanks for the help guys! Really appreciate it! I’ll report back once the new switch is in 🤞🏼

 

Nice! Order yourself a NON-LED test light and a multimeter too...it’ll make diagnosing electrical problems a lot easier!!

 

Colorado350, that’s funny you mentioned that. Was just looking at them this morning. Any suggestions on brands?

 

Installed new turn signal switch this afternoon... SOLVED!! ALL TURN SIGNALS WORK!! Thanks for all your help guys! I would have been lost without you. Greatly appreciated!

 

Any NON Led Test light will work. Do a little research on meters, my first one cost $35 and worked fine. My Buddy uses a Fluke process meter and amp clamp. Obviously a significant difference in price. I bought a Fluke T6-600 like new off CL for $100. Take the time to learn how to use properly, it’ll make your life easier!




Glad you figured it out!