Just a quick note to all that are digging into any problem or repair on their old Ford.

Diagnose and troubleshoot BEFORE digging into a repair. This may save you money and time in the long run...

I am usually a stickler for this concept but I fell into an easy sink hole to fall in.

No long story short here...

When I got my 76 F250, the heater core was bypassed because it was a leaker. No big deal, just a summer cruiser for me. Well there was a few chilly fall rides over the last couple years an I decided to try and tackle this monster earlier today. A little back story... The blower motor quit last spring and I just dealt with it last summer. Honestly, not a big deal and my kids got a kick outa the wing windows.

I gathered the parts last summer, but never got around to the repair. I have some time this spring a decided to dig in with my new heater core, blower motor, coolant and some new heater hose.

I started tearing things apart when I quickly realized that I HATED whom ever designed the dang blasted A/C coil / heater box area of my wonderful old Ford. Wish I could meet the ole boy face to face... The A/C coil soil only move a few inches out of the box regardless of how I pulled and stretched things. Working blind is fun right...guess so, I was having a blast... NOT!

Finally got to the heater core, yep, shot. Heater door, more fun. Blower motor, YES, even more of a party. Got the squirrel cage transferred over and stabbed it in place. While taking a break and sucking down ANOTHER adult beverage, I decided to hot wire the old bower motor and see what happened. Drastic turn of events here folks... The dang thing spun around like nobody's business... DIAGNOSE AND TROUBLESHOOT (subliminal message). At this time I wasn't quite sure how to handle the next few moments, so I had another adult beverage and thought about it...

I decided to go ahead and check the new blower motor operation to make sure I had the polarity correct before I put the heater core in place, you guessed it, THE DANG BLASTED THING DIDN'T TURN AT ALL!!!

By now, the wife is getting off work and we have plans for the evening, so all work stopped... Other than the gears grinding in my head!

So tomorrow, before I start to put this little sweat heart of a truck back together, I need to get power to the new motor to verify polarity.

I am thinking one of three things is bad. The dash switch, resistor or relay. Or any combination of the three. Something to note... Before the blower quit all together, it only worked on high.

Thanks for putting up with my rambling... I switched form barley and hop adult beverages to the Blended Canadian style a whole ago...

Just my funny story of the day... and to remind everyone to try and diagnose or troubleshoot problems before throwing unneeded parts at them.

On a side note... The blower motor that was removed was date stamped June 30, 1975 and it still rolled over when I put 12v to it...

 

It should of. If the polarity was reversed it would of just turned the motor the opposite way.

 

I knew that and that's what I want to check for before I get it all put back together.

The part that bugged me was the fact that it did nothing just like the "broken" one... because there is a problem other than the blower motor.

Oh well, I'll dig into it a bit deeper a little later this morning.

 

To everyone out there. If your A/C or heater blower has only high speed, that's a sure sign that the resistor has burned out. When the blower is on high speed, the resistor is bypassed.
If the blower doesn't work at all, first check the fuse, then check the switch. If that checks out, check for voltage at the motor. If there is power to the blower motor and it doesn't work, could be a ground issue, but most likely the blower motor is bad.
And yeah AK, trouble shoot first. Been there, done that . Thanks for the reminder .

 

Thanks Mike.

Pulled the resistor and it looks great, no signs of excessive heat at all.

Pulled the switch apart and other than dirty, it didn't look bad either.

Where are the grounds I should be looking for?

 

Ok, just pulled the relay apart and it's toast... Burnt toast.

 

I should of double checked the year of your truck.
'73 to mid-75 trucks used a different wiring set up and didn't use the relay. Mid-75 Ford changed the wiring and added a relay. In systems that have the relay, that's a very common failure point.
This is factory installed A/C only. Guys with heater only don't have the relay to worry about.

 

Mike, do you know if the three prong relay, that looks almost the same, just to the left under the dash by the steering column has the same values?

I would like to use it to test the blower motor.

Four Seasons P/N 35925

 

To be honest, I "think" they are but not sure. I tried to find the specs on them but came up with zip.

 

So, I swapped the relay over from the one by the steering column and it worked.

Now the fun task of reassembly...

Thanks for the help Mike!

 

Honestly I thought I was supposed to enjoy working on my truck. This SOB is fighting me all the way. Got the blower motor in, heater door in, heater core in. Now the heater door won't budge and I'm sure I just bent the end of the heater control cable.

The core has to come back out and the dash back apart again. Of this truck wasn't parked so close to the house, she might be a blaze...

 

Fixed the bow in the heater door. Re-did the seal around the heater core. The door moves smoothly now, but the cable is a different story... Tackle that one a different day. Started getting her back together.

Family plans this weekend, hopefully get to finish it up Monday.

 

Not that it makes you feel any better but my radiator exploded today. Sometimes it;s just one of those days. And yes I had several adult beverages after that happened.

I have to dig into the ac and if the engine is out I may just get it over with...

 

Just read your post, pretty amazing to say the least. Your hearing may take a day or two to fully recover.

I was starting to tune an old but newly installed carb the other day. While leaning over the radiator slowly advancing the throttle, I got a wicked loud backfire out the carb. Yup, too lean . My darn ear is still buggn me.

Cheers (a little blended Canadian on the rocks)

 

Cheers!