Blower Motor intermittent operation

You can pull the blower motor resistor and test it, but it is failing intermittantly and it may read fine and fail the next day. Electrical things are just like that, they fail off and on. Your instinct is right. A resistor might not be too expensive if you go to rockauto. Com.

Your very welcome. It is common for them to fail. If it is still intermitant, then it all that is left is the fan. If it still goes on beyond that, very unlikely, it is probably the control panel itself. It is behaving like failing resitor though, so don't let that information panic you, just thought you should have it.

Take care and come back to see us anytime for anything. We have the best team of Techs who are all very willing to help. Especially when it is someone mechanically inclined like yourself. It is a lot harder to work with someone who is not, but we still do it. It just takes a little longer. So, customers like you are a pleasure to work with.

Take care.

Dr. C

Climatronic or manual?

If it's manual, high speed does not go through the resistor. So, high
speed should work all the time even when the resistor low speeds are
burnt out.

Actually, it's the "thermal fuse" on the resistor pack that blows, causing
the low speeds to not function.

If it's climatronic, it's either the climatronic control module or the
control module for the fresh air blower (controls ground for
motor according to signal from climatronic).

Thomas

In the climatronic the module could be failing and it is circuit board level so there is not a way to check that without special tool. That is for the Automatic A/C.
I attached the manual A/C circuit. If you look at the resitor the HIGH setting has a squiggly line where it enters resistor, that is AC current. I have not seen any AC stuff in a car before, I am sure electronic control units use it but on circuit boards. It is very hard to understand AC circuits. I took DC circuits and touched on AC enough to go "holy Cow". Basically the elctricty is flowing through both the resistor and the direct connection at the same time. The current in the resistor is flowing in both directions so it is influenced by the resistor. I don't know why they did it this way except for the case where the resistor would fail. As long as there is 1 resistor out of the 3 that is able to carry current, as you can see in diagram all resitors are bridged, the current from the blower motor at high speed will take the path in/out, at the ame time, in the resistor. Only when all 3 are blown will the current change to DC and run straight to the blower motor. I have no idea why they would make it so complicated other than giving you the HIGH setting in case of resistor failure as it does not need resitance because it runs full throttle.
If you are at the point where only HIGH on the bolwer motor works then it is a self diagnosis that the resitor is bad and needs replacement. If you have any other speed it is probably still failing intermitantly and the fact that the ACcurrent converter is tied into some resitors would or could do some strange things as far as the way the motor behaves. AC circuits are really hard to figue out but at least we know that if you only have HIGH speed you definately need a new resistor.

Dr,

You are over thinking the diagram.

The squiggly line in the resistor pack is the "Thermal Fuse" that
I mentioned above/earlier.

The whole system is DC.

Yellow is power in, the rest are out to the switch. When the fuse
blows, nothing can exit the resistor pack back to the switch. Hence
only high speed works (because high speed is a direct power to the motor).

Thomas

You got me confused now! LOL

Yellow is the OUT terminal on the resistor.

Thomas

I looked up the squiggly line online AC current is a squiggly line with a circle around it and the thermal fuse is just a squiggly line. So, it makes sense now. I thought it was incredibly over-engineered and seemd odd. So, you are correct and the world makes sense again. I guess I should have taken AC circuits after all. Or remember DC better.
Are you still going with the resistor first? I believe it more likely than the motor. I am interested to know how much that resistor costs so let me know.