Any chance the other relay under the dash - not the blue one - controls the blower fan for the heat, defrost, etc.?

My fan has quit working recently but it died a slow, temperature related death. Which is what the turn signal relay did as well. One morning with temps in the single digits, the turn signals quit working. But later in the day were fine. Then that would happen occasionally with temps in the teens, then temps in the 20s, until finally they quit working altogether.

Now the fan doesn't kick on at all. But maybe after an hour of driving, it might. I feel sure if we had a day of temps in the 50s again it would run fine too.

I had to change the turn signal relay a second time already; the Motorcraft I put it only lasted six months. Now there is one from good ole Standard in there.

But doing those made me start wondering what the other relay sitting right next to it might control. Surely would be simpler than extracting the blower fan...

Heat Exchanger still working perfectly fine.

 

It doesn't work on any setting, even high? According to google the relay is under the hood, second 1 from the rear. The motor really isn't that bad to remove btw, hardest thing was undoing the plug with my sausage fingers.

 

@jackstraw The relay for the blower motor is in the Battery Junction Box. What you are referring to is the I/P Relay Block. It is more likely that either your blower motor or resistor is/are blown. It is a rule of thumb that you replace both at the same time. There is a good chance the pigtail for the resistor will need replacement too.

I have attached the wire diagram.

 

Well, was worth a question shot on it being just the relay, oh well. Thanks for the diagram, that is a good start on my next(s) project(s) I guess. I'm also guessing that in this day and age someone has probably made a video on pulling the blower motor that I will hunt for, eventually. I am getting pretty burned out on fixing things lately though and might just muddle through with that slow absorption of heat from the exchanger with no fan behind it for a while; the selection switch does still route the warm air where you need it to go.

Every project lately has only succeeded in revealing another, new project to complete, and that has been going on for over a year now, in a year with my fewest miles on the truck, ever. Replacing the turn signal relay for the second time only yielded a week of peace in that small area of the truck before the blower fan symptoms started showing. Usually each repair project has discovered a new need, instantly.


But on the topic of just that second relay under the dash - what does the "I/P block" control? Cuz whatever it does, I figure I will start seeing symptoms of that relay slipping, too, eventually. Probably the day after I finish replacing the blower motor, I figure.

 

Seriously the blower motor isn't that bad of a job. I replaced mine as well as the resistor a month ago in maybe an hour. Disconnect batteries, 2 bolts on fender to get the vacuum pump out of the way, fight the damn plug off the fan, then 3 little screws for the fan.

 

I'm still working on that. The FSM seems bound and determined to hide that information.

EDIT: Ah ha! It appears the other relay is the Trailer Running Lamp Relay. Sometimes all it takes is an 8-hour nap to come up with a new search strategy.

 

Excellent, thanks! I was a little surprised when I first gazed upon the turn signal relay that there was another relay directly adjacent. I am far more familiar with the relays in the fuse panel and near the brake fluid reservoir.

I am also dragging my feet on doing the blower motor as I am working 2 states to the south next week and am at this point just basically curious to see if it will kick on during an 8 hour drive, or what will happen in daytime temperatures in the 50s or higher. My truck always has a wild card when it comes to any electrical parts as it was hit by lightning about 6 years ago now and despite replacing the 2 main modules needed to run the engine, anything involving the dashboard can still show signs of a live gremlin still in there, ever since, with a few symptoms that occur for a while, then stop again, then start again weeks or months later.

So still haven't pulled up a YouTube account of this one but will soon - particularly as it sounds like I won't be going in from inside the cab?