mrgustave123

It is with great embarrassment my 1st thread is "I screwed up"; but as it's too cold to fumble around I turn here for guidance. I decided as a troubleshoot step (no starter response after 2hours of radio listening on known tested good battery);

I decided to replace the firewall mounted starter relay on my 2003 5.4 Lariat Crew Cab. They gave me a quality relay; BUT THE FORM FACTOR would not fit the pants-leg battery feeds. In my rush to get back to the part store I hooked up the old relay wrong (engine side red to bottom, other black shielded engine side to upper post. Started truck fine, but noticed a HOWLING followed by metal shreeking, followed by smoke seemly from passenger side exhaust manifold.

Then peaceful quiet, shut hood, drove to parts store, left truck running then home, then off and tried to start and NOTHING.

So, been searching and reading.
- I hooked the relay engine feeds up wrong BOTH engine side feeds should of been on lower large post.
- Howling and screech were likely my starter remaining engaged and finally failing (250K on truck).
- Smoke and acrid smell... wiring ? Starter?

No need to go public that you've also done this bone-headed move; but if you have and have fixed, I'd really appreciate some troubleshooting tips as all I have in my head is to remove and replace starter and go from there.

Thanks so much for reading; and hoping there some insight.
Paul

mrgustave123

So this is a fairly accurate schematic of many of the 10th gen f150's and it's confusing as hell as the physical doesn't jive with the schematic.

Battery C166 is on the same bottom LUG as C167 and the BK is on the top LUG and controlled by the IGN switch (S) which is not shown.

Which makes it a tad difficult to leverage wiring diagrams when trying to sort this out. Sigh....