The Good News Is ...

Well, the good news is I was finally able to figure out why the heater in my truck stopped working. Not exactly the heater, per se, but the blower motor that runs both the heater and the A/C. 

Last year about this time I replaced the blower motor and the blower motor relay (which is a giant PIA, if you wanted to know) so I was a little disgruntled when the blower stopped working this past spring. 

But, it was spring and then summer and no need for heat or defrost, right?

And so, I let the system go always in the going to get to it phase. 

The weather outside is frightful

And then the weather turned. Not enough to worry about, but enough to remind me I had things to take care of in my truck.

Earlier this week we had high temperatures in the teens and 20s, snow and freezing rain. 

I had no heat or defrost. It was miserable. 

So, today's one and only goal was to once and for all discover why the heater blower wasn't working. 

With a multimeter I checked the voltage at the blower and it read a perfect 12.5v, over 13v with the engine running. This meant power was at least arriving at the motor. So, I took the blower motor out and plugged it directly into the truck's battery where it fired up with all it's might.

The motor was good and it was getting power. So, why wasn't it working?

Worried I was going to have to turn the truck into a mechanic and pay an exorbant cost to troubleshoot an electrical issue I did what I always do and turned to YouTube where I watched multiple videos, all of them going over the same points. Until one of them causally mentioned it might be the control unit switch. 

At that point I pulled the dash out and checked the control panel. Nothing had become disconnected and nothing seemed burnt up nor otherwise discombobulated. 

I was just about to give up when I remembered I had an older ECU (environmental control unit) in the garage. I grabbed that and plugged it into the connectors and the blower motor fired up!

But wait, there's more!

I carefully put everything back together and ... the blower motor stopped working.

WTF?

Frantically, I began checking the fuses thinking one of them had popped.

Everything was perfect, so I was back to a WTF moment. 

Once more I pulled the dash, the radio and the ECU out and checked everything. The new (old) ECU seemed fine and yet the blower motor wasn't blowing. So, I pulled it out and plugged the original ECU back and ...

... the motor began blowing! 

Once again I carefully put everything back in its place, this time leaving the motor running the entire time to see if anything I did caused a failure. Luckily, nothing did. 

I drove all the way back to town (my garage is in the sticks) with the heater running and the windows open.

During my test of the ECU, after ensuring it was running and before putting everything back together, I checked the actuator doors to see if defrost, upper and lower areas worked. I could hear the motors on the doors working but other than hot to cold nothing actually changed. 

But hey, I'm not going to freeze to death and that's really all that matters, right?