Blower motor works without some wires

[Farrar]

I have a strange one now. I connected the blower motor and although one of the wires is disconnected (the double black one), it works just as it is supposed to. When I connect it, the blower motor stops working. What gives?

[DMC5180]

You may just have an intermittent connection on the Ground Cluster wires (Black). Wiggle things a bit with the switch in position that was running before. Please post a pic of the wiring connections under there.

[Jonathan]

Farrar, aren't there a couple different circuits for the blower motor and which speed it is running at? Like, if it is on speed 1 or 2 it might be okay, but say 3 and 4 don't work. Might have something to do with half of that being wired okay and the other half having some issue?

[Bitsyncmaster]

I have a strange one now. I connected the blower motor and although one of the wires is disconnected (the double black one), it works just as it is supposed to. When I connect it, the blower motor stops working. What gives?

The motor is getting a ground through the case somehow. Don't know why connecting the ground wire would stop it. My guess is you have a bad blower motor.

[dmc6960]

I think this will be a case of a picture being worth 1000 words. You could have a "backwards" motor which requires the case to be hot with the primary lead receiving the ground. I ran with one of these for 10 years.

[LEVY]

I think this will be a case of a picture being worth 1000 words. You could have a "backwards" motor which requires the case to be hot with the primary lead receiving the ground. I ran with one of these for 10 years.

What kind of motor you are talking about?

It is possible to wire the motor incorrectly at time of manufacture, it is almost impossible to make it work because of way they are grounded , unless you really want it to work and change the grounding.

Automotive industry always use black for ground or negative and any other color for positive. Household industry, on the other hand use white for ground and any other color for the live wire (can't say positive here).

And for the O.P; I would agree with Dave, something should be wrong with your motor, that wire was disconnected by the P.O. for a reason. Does your motor have more than one speed working?

LEVY

[Farrar]

You may just have an intermittent connection on the Ground Cluster wires (Black). Wiggle things a bit with the switch in position that was running before. Please post a pic of the wiring connections under there.

19290


Farrar, aren't there a couple different circuits for the blower motor and which speed it is running at? Like, if it is on speed 1 or 2 it might be okay, but say 3 and 4 don't work. Might have something to do with half of that being wired okay and the other half having some issue?

When I say "works as it should," I mean that it works on all speeds.


The motor is getting a ground through the case somehow. Don't know why connecting the ground wire would stop it. My guess is you have a bad blower motor.

There's more than one ground, or so it appears.


I think this will be a case of a picture being worth 1000 words. You could have a "backwards" motor which requires the case to be hot with the primary lead receiving the ground. I ran with one of these for 10 years.

Maybe that's it; it's not NOS -- I got it from a cross-reference list and installed it a while ago. You're probably right.


that wire was disconnected by the P.O. for a reason. Does your motor have more than one speed working?

When I say "works as it should," I mean that it works on all speeds.

The blower motor was disconnected by me when I replaced the evaporator last year. At the time I had only the highest speed, and that was with all wires connected. Now with what is connected as you can see in the photograph above, it works as it should, by which I mean it works on all speeds.

I guess I'll just leave those leads disconnected; it seems odd but it works.

Thanks!

[dmc6960]

What kind of motor you are talking about?

It is possible to wire the motor incorrectly at time of manufacture, it is almost impossible to make it work because of way they are grounded , unless you really want it to work and change the grounding.


Siemens: PM105. This motor has an identical form factor to the DeLorean blower, but it is internally wired to spin backwards unless you swap the 12V and ground. While normally impossible on a vehicle, it is quite possible to do on a DeLorean as it screws into just a plastic housing. I ran with a backwards-wired PM105 for 10 years. Finally replaced it with a proper Siemens PM106.

[Farrar]

I ran with a backwards-wired PM105 for 10 years. Finally replaced it with a proper Siemens PM106.

I'm guessing the one I have, which is made by Four Seasons, is similar. Thanks for the tip. Now I know which one to get when this one craps out. :)

[Exolis]

So with Picture as shown, those 2 wires connected, everything works, correct? If so, it seems like correct setup according to wiring diagram.

Do you have pictures of the other 2 wires in question to cause motor to be INOP? If you have a voltmeter, you can check for ground float by measuring the voltage at that terminal with wires connected and measure with battery GND. If it's over 1V, chances the GND is too small/dirty to handle the Blower Motor and whatever else going to that ground. This is a bit confusing issue from the sound of it.

[dmc6960]

Agreed something is still awry with this. Curious what your voltage readings are on all the leads. Use a known good 12v and GND to eliminate uncertainties. Also test with blower on speed 4 to eliminate the resistor drop. What is the exact Four Seasons part number you have?

[dmc6960]

Confirming with my own car, everything seems good here. The only thing not connected in your picture is the other end of that "red" wire. That is a noise filter capacitor, the other end should have its own female spade terminal and plug into on of those other two leads on the ground. Your motor is not currently wired backwards. Not all three of that "triple lead" are used, only two.

[Farrar]

Do you have pictures of the other 2 wires in question to cause motor to be INOP?

The other two wires are a black ground wire, and a red wire which has a giant capacitor inline. You can see the red wire in the picture, just not the other end with the cap and female terminal on.

Here is a picture which better shows the other ground wire which is not connected. It's difficult to tell from the picture, but of the two black ground connectors in that picture, the one that is connected has two wires, and the one that is not connected has one. All of the black ground wires disappear into the harness.

19298


The only thing not connected in your picture is the other end of that "red" wire. That is a noise filter capacitor, the other end should have its own female spade terminal and plug into on of those other two leads on the ground. Your motor is not currently wired backwards. Not all three of that "triple lead" are used, only two.

Ah, radio noise suppression -- fine, I can snip that one off, then, and replace the pink/black connector with a proper one. Sorry I couldn't get the end of that red wire in the pictures. My camera is funny about focusing on small things -- all of the other pictures were just blurry.


Curious what your voltage readings are on all the leads. Use a known good 12v and GND to eliminate uncertainties. Also test with blower on speed 4 to eliminate the resistor drop. What is the exact Four Seasons part number you have?

The blower motor is a Four Seasons 35589, which I bought in January of 2011, in advance of a complete a/c rebuild. Obviously, I didn't install it right away... I bought it because it was on sale and I knew I'd need it when I finally got around to replacing the rest of the system. Obviously, it took me some little time to get around to it... :p I'll try to get some voltage readings soon.

Thanks, everyone! Maybe I will be able to drive my car this summer! :D