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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

Intermittent failure of turn signals

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Old May 21, 2026 | 08:41 PM
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Intermittent failure of turn signals

So I recently replaced the MFS and the signal flasher thinking the electronic one had failed. Everything worked for about a week and now it has quit again. I have studied the wiring diagram and I do not have a clue what could be fouled up. Truck has not been butchered as I found it w/ less than 95K original miles. Been driving it for right at 2 yrs this July. The emergency side works fine so I know the bulbs are good as is the ground or they wouldn't work. I have verified w/ test light that power is making it to the flasher socket in fuse panel. i've swapped em. flasher (original wagner flasher) to the turn signal side w/ no change. I am at the point where I need to just turn the signal on and start wiggling everything from the trailer plug (could be a tee splice issue) to the brake light switch and the ignition switch. Fuse has checked in the fuse panel so I am about out of ideas. Anyone got anything else I should inspect?
 
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Old Yesterday | 07:59 AM
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Who made the new multi-function switch?
I had to put 3 Autozone ones in my buddies Lincoln before we got pissed and found a NOS Ford one on Ebay
His would do the same thing, work then not work and was plugged in good
You might check the plugs on the back of yours, as that is the most common problem IMO
Sometimes those wires get pulled out of the connector, and the connector would be in place, but the pulled out wires would not make contact
Intermittent flashers are common too, swap your TS flasher with the one for the hazards, the hazard flasher generally never gets used, and they are usually like brand new
 
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Old Yesterday | 11:55 AM
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From: SW GA
Originally Posted by manicmechanic007
Who made the new multi-function switch?
I had to put 3 Autozone ones in my buddies Lincoln before we got pissed and found a NOS Ford one on Ebay
His would do the same thing, work then not work and was plugged in good
You might check the plugs on the back of yours, as that is the most common problem IMO
Sometimes those wires get pulled out of the connector, and the connector would be in place, but the pulled out wires would not make contact
Intermittent flashers are common too, swap your TS flasher with the one for the hazards, the hazard flasher generally never gets used, and they are usually like brand new
The new switch is an Autozone one and it was not local. I had put an unknown switch from JY in about 6 months ago only because the stalk had a plastic door that kept falling off. It had no markings and I snagged it because it looked nearly new. I still have it so I may direct it and determine what is going on. I already tried swapping the em flasher which was original ford (made by wagner) and it made no change. I will check the wires in the connector as that is a possibility due to the tight angle the wiring is subject to.
 
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Old Yesterday | 12:22 PM
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Originally Posted by generalee
The new switch is an Autozone one and it was not local. I had put an unknown switch from JY in about 6 months ago only because the stalk had a plastic door that kept falling off. It had no markings and I snagged it because it looked nearly new. I still have it so I may direct it and determine what is going on. I already tried swapping the em flasher which was original ford (made by wagner) and it made no change. I will check the wires in the connector as that is a possibility due to the tight angle the wiring is subject to.
what does the turn signal do? fail to flash but the dash indicator illuminates no blink?
If you HOLD the switch in the direction with a bit of force, does it work?

Ive had where I need to operate the lever at the speed I want it to blink and thats from the column cancel cam (pre 92 columns only)

I used to have that problem intermittently, i have since lost the problem, I think the only thing ive done is pulled the large connector on the cab, cleaned terminals ,and reseated and also possibly cleaned up body grounds and the frame ground.
 
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Old Today | 12:45 PM
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From: SW GA
I have activated the switch in emergency mode and it works fine. I removed the turn signal flasher and verified 12v across the two connectors when switch is activated. I have left the switch active and wiggled and pulled on brake light switch, dashboard and steering wheel areas trying to get something to trigger. The flash to pass worked as does the high beam activation. Wipers and delay work fine too. I will I'll next pull the switch and check the circuits 44 w/ 9 & 3 for left side and 5&2 for right side. With switch activated those circuits should be closed. If that is the case then it must be in the wiring between switch and flasher.
 
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