need to test my a/c blower motor

[baltimoremm]

My AC blower motor stopped blowing. I dont think its the control head unit, since i can hear the blend doors moving when i change from max ac, to defrost, etc, so I'm hoping its just the motor itself
i'd like to test the motor by hooking it up to the battery as some have suggested on here. Can anyone help me out w/ a how to on this? Do I just disconnect the harness and attach two wires? if the motor ends up working when connected directly to the batter, what is the next step in diagnosing the problem?
thanks in advance for any pointers

[Zack]

The first step is to see if you have power going to the blower motor.
By doing this you will have answered the question you originally asked.

[Marauderjack]

Probably the BCM (Blower Control Module)....a real PITA to replace but not expensive and can be done in the driveway with a little patience!!!:beer:

It lives in the plenum behind the passenger side cam cover.....photo attached!!

Good Luck!!

Marauderjack;)

[RF Overlord]

Be careful when disconnecting harnesses and applying power. The blower speed control on this car is not just a simple resistive divider network like in most older cars; it uses a PWM (Pulse-Width Modulation) control module to vary the duty-cycle of the voltage applied to the blower motor.

I'll look at the FSM when I get home this evening and see what the troubleshooting steps for an inop blower are and post them here.

[baltimoremm]

thanks guys. i'd like to make absolute sure its not the blower before getting into the more difficult stuff.

[Krytin]

I had this problem on my '03 MM & '04 CVLX Sport.
The MM went out when I got to Carlisle this year.
After checking for voltage - it had battery voltage but the ground was open on the harness - the thing started working again all by itself after a few days.
A month later the exact same thing happened to the CV.

PFM!!!!

You might want to check your conections and wait a few days..........

[Marauderjack]

Just unplug the blower and jump it directly to your battery.....makes no difference as to polarity (DC motor runs both ways)!!:beer:

If OK it will run wide open (HIGH SPEED) and scare the poop out of you.....don't ask how I know!!!:eek::shake:

After it checks OK the fun begins with the BCM!!:rolleyes:

Good Luck again!!

Marauderjack:beer:

[Wires]

Be careful when disconnecting harnesses and applying power. The blower speed control on this car is not just a simple resistive divider network like in most older cars; it uses a PWM (Pulse-Width Modulation) control module to vary the duty-cycle of the voltage applied to the blower motor.

I'll look at the FSM when I get home this evening and see what the troubleshooting steps for an inop blower are and post them here.

The blower is fed constant 12V, and the ground resistance is modified by variable pulse width to the FET in the control module. However, in "full on" or high, a relay in the control module switches, and the motor is hard grounded. (by relay.)

So, as said above, disconnect from the harness and apply 12v to the motor to test.

Yes, that module is FUN to replace.

An easy way to test is to buy a new module and simply leave it "hanging" connected to the harness. That way you can check it before you go through the trouble to remove the old one.

See this fine thread for more info:
http://mercurymarauder.net/forums/showthread.php?t=43165 (http://mercurymarauder.net/forums/showthread.php?t=43165)
(OK, I think this is the link I meant to post. I didn't mean to be a wise-a and post a link to this thread!

[Vortech347]

Do what MarauderJack said. This same thing happened when mine stopped working in my 03'

Its very easy to replace, its not hard. About 20 min.

[RF Overlord]

The blower is fed constant 12V, and the ground resistance is modified by variable pulse width to the FET in the control module. However, in "full on" or high, a relay in the control module switches, and the motor is hard grounded. (by relay.)I had the right circuit, but the wrong location. :D Thanks for the clarification...

[ixlr8]

Man there is some great information here for all of us MM owners...just one question because this has now just happened to my car TODAY. Did anyone smell some burning plastic or other electrical smells before the blower quit working?

I had my blower on manual control at a low setting, turned the car off, went into the bank, came back, turned car on an fan was just how I left it and it was working. I decided it was time for some a/c so I pressed "automatic" and the blower maxed out and blew cold air for a minute, then I smelled something burning that I hoped was outside the car but it was pretty strong, then the blower just stopped. Head unit working ok (vacuum tubes can be heard working), fuses are ok also.

Advice?

Also on a side note, I noticed this morning when I was going to work that the voltmeter was on 15 volts??? It normally starts at 14 and works its way back to 13 when idling warm. Now it's idling at 14 warm. I do know a bit about electronics - and I know too much voltage will kill an electric motor, but surely not an extra 1-2 volts???

Any and all input is appreciated!

[Wires]

Man there is some great information here for all of us MM owners...just one question because this has now just happened to my car TODAY. Did anyone smell some burning plastic or other electrical smells before the blower quit working?

I had my blower on manual control at a low setting, turned the car off, went into the bank, came back, turned car on an fan was just how I left it and it was working. I decided it was time for some a/c so I pressed "automatic" and the blower maxed out and blew cold air for a minute, then I smelled something burning that I hoped was outside the car but it was pretty strong, then the blower just stopped. Head unit working ok (vacuum tubes can be heard working), fuses are ok also.

Advice?

Also on a side note, I noticed this morning when I was going to work that the voltmeter was on 15 volts??? It normally starts at 14 and works its way back to 13 when idling warm. Now it's idling at 14 warm. I do know a bit about electronics - and I know too much voltage will kill an electric motor, but surely not an extra 1-2 volts???

Any and all input is appreciated!

Mine did the same thing. I had the same reaction. "It's something outside the car."

Then the blower stopped working.

I realized that despite my trying to wish the problem away, my blower control module had died.

Do a search, there are several threads about replacing it. Here's one in which I wrote a reply about the fun of changing it. (Ignore the parts about deciding whether or not it's the control module or the A/C headunit) Because the module is in the air-stream, if you smell burning, chances are that this is the problem)

http://mercurymarauder.net/forums/showthread.php?t=43165

Other fine threads:

http://mercurymarauder.net/forums/showthread.php?t=44631&highlight=blower+module

http://mercurymarauder.net/forums/showthread.php?t=41261&highlight=blower+module

Hmm, from searching, it seems some have the burning smell, some just stop working (open, no fan) and some stick in the full on mode (relay stuck or FET shorted)

[ixlr8]

Thanks Wires!

I did bump into that first link earlier today. Glad to know that the burning smell is not an isolated incident though. Looks like a new BCM is in my future.

Thanks to all who contribute on this forum...I don't post a lot, but I'm here often! It's threads like this that make this website an invaluable tool!

I WILL post results.

[ixlr8]

http://www.mercurymarauder.net/forums/showthread.php?t=48707

[Wires]

http://www.mercurymarauder.net/forums/showthread.php?t=48707

THATS the thread I couldn't find.

It takes more patience and or ability than I have to take that thing out without removing the heater hoses.