Blower Motor Resistor Issue

[deeman]

I diagnosed a bad blower motor resistor pack since I only had the highest fan speed working. I bought a new resistor pack and removed the old resistor pack which was fairly rusty.
The connector was so stuck onto the resistor pack that I bought another kit with the resistor pack and the pigtail connector.
I was extra careful to match the wiring from the old pig tail to the new one.
I Installed one of the new resistor packs and attached the pigtail harness and nothing. No fan at all.
Checked the 30amp fuse and its fine.
I pulled the pack out to inspect and it looked fine
With the new pigtail laying accross the engine compartment (not fully installed) I connected the second, new resistor pack and the blower worked fine. Cool.
I then installed the second resistor pack in place (I didn't even remove it from the pigtail - I just lowered the assembly into place and secured the two screws.) and NOTHING
Checked the fuse - it is still fine. I am at a loss.
To recap - the second new pack worked while laying on the engine but when installed it stopped working.

I did not disconnect the battery wires - maybe that is the issue. I did a ohms test on the second pack and it ohm'ed out fine.

Thoughts?

 

[franklin2]

Is this the conventional resistor pack with the exposed springs? Or some sort of electronic thing.

 

[deeman]

Is this the conventional resistor pack with the exposed springs? Or some sort of electronic thing.

exposed springs pack, thanks

 

[sgtsandman]

It might be a broken wire causing intermittent contact depending on how the harness is flexed.

Look for common wire(s) if it is a problem at all speeds.

Also, while not common, something to look for. How do the terminals on the fuse look? If there is brownish stuff on the fuse terminals, it’s the fuse even if it looks fine otherwise. I just ran into this being a problem a few weeks back with an inop fuel pump.

 

[franklin2]

exposed springs pack, thanks

Yes, I would look for breaks in the spring coils. And what happens to me with these things is Ford added a temperature fuse in with the springs. It's just like they put in coffee makers, a little silver looking cylinder. Usually this burns out and then the whole resistor pack doesn't work, it just works on high speed which doesn't use the resistors. You can ohm the fuse out and see if it's open. You can do this at your own risk, but I usually jump around the fuse to get it working again. I guess you could look for a temp rating on the outside of the fuse, I think they do sell new ones.

 

[4x4prepper]

From a text file on my hard drive, from where I got it, I do not know.

"The replacement thermal fuse is a Radio Shack part #270-1320."

is a thermal fuse rated for 151 degrees celsius and approx. 300 degrees farenhiet(sp). I went to my local Radio Shack and they looked it up on their data. According to the Radio Shack manager. The replacement thermal fuse is a Radio Shack part #270-1320. This cost a total of $1.69. I soldered it in to replace the original, replaced the connector and turned the blower switch to each setting with great results. My blower motor works great! Be sure to use a heat sink in soldering in the thermal fuse to insure that the soldering iron heat does not blow the thermal fuse

 

[deeman]

Wow - thanks so much guys! I will give these suggestions a try and report back.

 

[deeman]

Okay, spending a beautiful Saturday with my head in the engine compartment! So, here is what I now know:

1. The 30amp blower motor relay is good - tested
When I connect a volt meter to the blower motor connector (which connects right to the blower motor) I see 12.2 volts on the high setting and all settings for that matter BUT the blower will not turn on. I wonder if I have a bad blower motor.

 

[franklin2]

I am not sure what you are working on, I would think a 2008 would have something different. But if you are messing with the old school resistor spring pack, then most of those older type systems ran 12v to the fan directly, and they ran the ground for the motor through the controls. In other words, in high the speed switch would ground the motor directly to ground. Any other slower speed the motor ground ran through a resistor selected, and then went to ground.

What year and model are you working on? The only thing in your signature is a 2008 and I would have though they went to electronic speed control by then.

 

[deeman]

Thanks very much Franklin - I hope you are able to see my signature with - 2008 Supercab XLT 2WD 3.0l - listed. If it's not visible I will fix that so others can see.
It is an open resistor pack on my truck.

I can't help but feel the blower motor is bad. Even when it was working about 3 weeks ago I could tell the motor would speed up and down on it's own - when in idle speed it would be very slow and then speed up when I got up to speed - not sure if that is a symptom of a faulty motor or not.

 

[franklin2]

Here's the diagram for your truck's blower. You can see they still indeed feed the blower with 12v from the blower motor relay, and the relay is activated by the climate controls. You said you were getting 12v on the yellow/green? So we can call that good.

You can see how the speed selector switch in the climate controls picks which wire to put to ground, which is the black/yellow wire. It puts the violet orange directly to ground for high speed, and selects the other wires to ground which go through the resistors.

If it's not working at all, I would be suspicious of the black/yellow ground wire. Not sure where it's located though. If you had a jumper wire, and clipped one end to the battery negative or a good ground somewhere, and then touched the other end of the grounded jumper to the violet/orange wire at the resistor pack, the motor should run at high speed if the climate control is telling it to run.

 

[deeman]

Thanks so much Franklin! So I did get 12.22 volts on the wire connector which plugs into the blower motor and yet when reconnected the blower does not run. This still makes me think it's a bad blower.

I will try your suggestion of running a ground to the violet/orange wire to see what happens. To be clear in your suggestion am I running the wire to the female connector on the wire connector with the resistor removed, or connect the resistor pack and then touch the grounded wire to the resistors soldered to the pin corresponding to the violet/orange wire? Or asked another way, should the resistor pack be plugged in with your suggestion or not?

Many thanks for taking the time to assist me. I am very grateful!

 

[franklin2]

It doesn't matter if it's plugged in or not. So whatever is easier to do.

 

[4x4prepper]

Using a remote starter switch and alligator clips (note the Bosch one will melt with a direct 15 amps ...) you can test the blower motor. I use fused NEG and POS leads. I see surplus center has some blower motors, I am trying to figure out the RPMs on my B2 and see if I can upgrade to a faster motor. I think almost every blower motor takes the exact same squirrel cage, shaft size wise.

 

[Burnsy]

So how did this resolve?