I am looking for ideas on these baffling wiring fault mysteries for items I (they) have not yet checked
I had a radiator shop replace a heater core and it ended up with no front turn signals ( rears fast flash )
and the brake warning light stays on solid
mechanic said he did a snap on scan and found a code or something saying it was brake fluid related not parking switch
but the low fluid sensor and parking brake switch are OK and ruled out
my first thought was clock spring but all my XLT steering wheel controls function and mech said he kept it locked when they took it off
he rechecked all the plug connectors involved
said he's done dozens of F150 heater cores ( but maybe not this new, its the 2010 can of worms)
maybe something in the steering column ?
maybe yanked or pinched wires somewhere ?
multi function switch connector got yanked ?
why just only the two front signal wires lost continuity ?,front signal bulbs are still working as parking lites, flashers work only in rear
Previous to them taking the steering column off and swinging the dash out to get to the carefully designed to be inaccessible heater core, all of the electrical worked flawless for 247,000 miles
I know you cant diagnose from a keyboard but maybe someone has been through this and has some ideas ?

there might be something to all the mechanics in my little farm town refusing the job saying something like this always happens on the later model F150s so they just flat out refuse

 

fast-flashing signals often means the wrong bulb is in the socket.

 

there are some members here that post up schematics, hopefully one will jump in. Definitely odd the rears flash but front dont.

a quick google search showed some replacing the bcm (last option and least likely imho). others talking about the multifunction switch - wonder if a wire got pulled loose or something.

we had something similar with our f550 at work, cant remember the exact circumstances but they had to do something with the dash and then turn signals didnt work correctly. Ended up replacing the turn signal stalk/multi function switch. Maybe someone can post a diagram or you can search for one on that and use a volt meter or test light to see if youre getting the flash signal out of the switch (test the rear signal to verify)

 

Meh...I'd never pulled a dash before and I did it by myself in my driveway. I guess nobody wants to work anymore.

I only have the 2011+ manual, the 2010 was an orphan transition year with a different BCM setup. On a 2011 the BCM drives the bulbs, so I'd start out looking for voltage at the bulb. if no voltage, keep working backward toward the BCM until you find out where voltage is getting lost.

 

Thank You yes , that is the direction I was headed , I was going to throw a Multifunction Switch at it (to rule it out ) Until I found out they are $350 at Oreily's , the 2015 turn signal switches are still $60
I asked the local Ford dealer if I could buy a wiring diagram but they just said to go online and get access to the ford system....UGH
service writer said they would take a look at it for 3hrs ( $500 ish) and suspects ( by experience) it is either the multiSwitch or in the Instrument panel circuit board that supplies reference voltage grounding signal and that the turn signals and brake warning light are unrelated unless the problem is the instrument panel because everything runs through that circuit board
I brought up with the Ford service writer that the only place where front and rear turn signals split signal path is the four pins in the Multi Switch and he said Not True it also splits path inside the instrument panel out to each signal lite after getting signal from the Multi-switch and everything is triggered by ground to relays but the relay and flasher device provide the pos side
5V reference voltage at the brake fluid warning sensor sends a signal to the instrument panel circuit board when it gets a low fluid reading which connects ground)
Poor mechanic who did the job got screwed over by this common occurring problem every time you remove a late model Ford booby trap dashboard

 

I would like to get the $390 motorcraft part with 2 year warranty but I managed to find one on amazon from US for $50.
there are a lot shipping from china on ebay still
hope it works ok
typically with switches it is the OEM subcontractor pushing them out the back door with less QC control

 

this is true thank you
but in this case the 2 separate problems were caused by removing the steering wheel and pulling out the dashboard to replace the heater core and AC expansion valve

 

This is a fairly common problem as the service writer said
evidently these instrument clusters are fragile
https://www.f150forum.com/f38/instru...cement-231419/

 

Happy Ending
original mechanic found it on a second look after a few hours, turned out to be a connector problem at the BCM (Body Control Module)