Auto A/C front blower shuts off on High setting (all other speed good)

[Space Monkey]

2012 Expy Limited. I have replaced both the blower motor and the fan control module, including new harness pigtail for the fan control module. Originally, the motor control module melted on pin 2 (yellow with green stripe, next to black with white stripe), module 9L34-19E624. I replaced the module with a DORMAN 973-506. The new module will run in all speeds except the highest...it will run for about 5 seconds and then the blower shuts off. It feels very hot, so I am assuming it is cutting off due to heat. I have ordered the FoMoCo controller module.

While I wait for the new controller module, is there any ideas on why the module is getting hot? Yes, the DORMAN part could be a pile of crap, but is there possibly another reason why I can't run the blower on the highest setting?

View attachment 20857

 

[Space Monkey]

This was the motor control module that was removed.

 

[ExpeditionAndy]

Dorman makes a lot of OEM parts so it could very well be the same part as the factory part. It is possible that you have a fan with a tight bearing that is causing it to draw more current and heat up. The thermal overload will shut it down when it gets too hot. I could also cause the module to overheat because of the excess current draw. That's just my 2 cents worth. At least it is something to consider.

If it is easy to remove the fan (and I don't know if it is) you might want to pull it and see if it turns freely. You could also run it and after it shuts off pull it again and see if it's harder to turn when it's hot.

 

[Space Monkey]

I installed a new blower motor (also bought one for my 07 expy). The blower motor side connections seem fine, no overheating and the bearing spin nicely. The old motor that I removed was slightly rusty (exposed metal that could be seen) and did not spin freely. Pretty sure it is not the motor at this time.

 

[ExpeditionAndy]

I installed a new blower motor (also bought one for my 07 expy). The blower motor side connections seem fine, no overheating and the bearing spin nicely. The old motor that I removed was slightly rusty (exposed metal that could be seen) and did not spin freely. Pretty sure it is not the motor at this time.

Okay well that's good to know, now you just have to figure out why it's turning off. Hopefully @stamp11127 will offer some thoughts, he is great on this stuff.

 

[stamp11127]

When connectors melt that is an indication of poor or insufficient contact at the male & female connection point. If there isn't any indication of the wire insulation overheating, the wire gauge size is adaquit.
Since you cut the connector off you should solder and heat shrink the new pigtail on to the existing wires. If you don't then you have added another poor connection point.
Butt connectors are junk unless you use the type with solder and shrink tubing built-in @$1.00 each online.

Where is the module mounted? Does it have a metal back that could act as a heat sink?

 

[Space Monkey]

The control module mounts on the side of the HVAC case, pretty close to where the blower motor is mounted. The DORMAN module has a good sized aluminum heat sink just like the OEM. I did solder and heat shrink the new pig tail in and I hit the spades with de-ox-it before connecting. It seems like I am hitting the thermal overload of the module...I can run it in all speeds but high.

 

[stamp11127]

Did ford provide a method to cool the module such as a small duct?
What good is a heat sink in dead air?

 

[Space Monkey]

The heat sink is in the ducting and there is also a tube from the blower that blows past the heat sink.. With the A/C on, it should have plenty of cool air.

 

[DesertDawg]

Hmm, I have a similar problem with my front blower with the A/C. Mine is intermittent and it has been for over a year now. The strange thing is - it works intermittently. When it's not too hot out it works most all the time. When it's hotter out, most of the time the blower won't work until it decides to kick on. I used to be able to hit a bump, go up and drop off a curb and it would kick on but that trick seems to no longer work but a lot of the times it will kick on after driving it for 20 minutes or so. I was starting think it was related to the heat and outside air temperature but, two weeks ago when it was 121 degrees here in Phoenix the blower kicked in about 20 minutes after I started it and started driving to a destination.

I asked a mechanic about this issue shortly after he changed out my radiator and he stuck his head under the dash and found some pin connector that looked somewhat melted and said it looks like somebody screwed that up and said it must have been some aftermarket device I put in. I've never installed any aftermarket electronics. The back air works fine.

Additionally, when I had my radiator changed out last year, my outside temperature gauge is off (high about 10 degrees now). Any thoughts on that, too?