This has been an issue on and off for almost a year now. I have a 2002 F150 Super crew, and the turn signals intermittently will stop working (obviously related, when my turn signals stop working, the temp gauge above the windshield also turns off) Sometimes when I start the car they are off, and will turn on while I'm driving, sometimes they will be on when I start the car and turn off while I'm driving.The hazards always work.
I replaced the flasher relay module in the spring. I also installed a new MFS, as well as replacing both wiring harnesses for the MFS (including adding wire extensions).
When the turn signals are off, whether I turn the signal left or right nothing happens. However, if I step on the brake pedal, I can wiggle the MFS and it clicks, and sometimes will even flash the light.
Not sure what else to check!

 

Check for water/corrosion in your fuse box and GEM.

 

I had been having trouble with the fusebox in the spring, so I pulled the fusebox apart, scrubbed it, and reassembled it, which cured the issues I was having at that time (lights flashing on and off, doors locking and unlocking, etc). The GEM looked fine, and the corrosion is gone, but could that still be causing the problem?

 

Could be. Anytime water gets in there, you never know 100%.

My suggestion is to replace it.

 

You know how long it took me to pull that fusebox apart and reassemble it (3 times...)!!!
I guess I'll have to order a new one. Thanks for the input

 

Gee, you got more patience than me... I would've taken it apart once...... maybe twice... but not thrice... lol

 

I wonder if you have a water leak from the windshield.... A lot of vehicles are notorious for this, especially older vehicles.

My neighbor has a 01 supercrew, and says his windows leak like crazy.

 

I did have a leaking windshield, which was causing the fusebox to keep getting wet (leading to me rebuilding it three times). Finally replaced the windshield in the spring. No leaks since.

 

Not only will windshield leaks mess up the fuse box, it's also hard on the GEM. You need to pull it and check it carefully.

Need truck info to look up a GEM, Rock Auto sells remans, go to Electrical, then Body Control Module:

Engine
2wd or 4wd
If 4wd, electric or manual shift
If 2wd, with or without power group

 

You guys seem pretty confident that this is an issue with the GEM. I've already replaced a bunch of fuses, rebuilt the fusebox, cleaned the GEM, replaced the MFS, and spliced and rewired both wiring harnesses for the MFS, trying to fix this problem. I'm just want to make sure this is the problem before I spend another $150 on a new GEM.

 

Hey guys, wanted to add one piece of information that may or may not be related: I've noticed that it's been 55-65F every day this week and, rain or shine, my turn signals have been working. Would the outside temperature mess with the GEM?

 

I suppose it could - my odometer is intermittent and it seems to go off when it's warm. Run the A/C for a bit and it comes back on. That's not a GEM issue, it's a cold solder joint in the cluster. However, same principle?

 

That's what made me initially think it was an issue with the MFS harness, I assumed that one of the pins didn't have a solid connection, but replacing the MFS and the harnesses didn't fix it.
BTW, I also have the issue with the intermittent odometer, so that's good to know.

 

Intermittent odometer fix:

https://www.f150online.com/forums/ar...er-repair.html

https://www.f150online.com/forums/ar...-new-post.html

 

As a side note, if you aren't good at soldering, or get the heebee jeevees about it, see if you know of someone that is electronic savvy. Or, bring it to your local tech school (community college), and find the tech and trades folks.

Just show them/print out what glc put up above. For someone that has had a little time behind a soldering iron, it won't be a problem for them (or shouldn't).

I have fixed these and many other things for my students (or others) for free (well, I often times get a DD card, or food, etc). Yes, I work for food...