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Ask Doug C. Your Own Question

Doug C.
Doug C., ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 6399
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Blower motor will not come on i have checked all fuses and conections

Customer Question

the blower motor will not come on i have checked all fuses and conections
Submitted: 3 years ago.
Category: Mitsubishi
Expert:  Doug C. replied 3 years ago.

Doug C :

Hi,

Doug C :

Is the vehicle present for some quick checks?

Customer:

yep

Doug C :

Great

Doug C :

What I would like to do first is go out to the vehicle, and reach under the passenger side dash and unplug the blower motor. Once it is unplugged I would like to know two things:
1) are the pins oriented like this: -- -- or like this: | --
2) is there any discoloring or blackening around the connector end, any evidence of the wiring getting very hot, any crusty material, etc

Customer:

????second style we have already replaced them once ( [,--) something keeps burning them out

Doug C :

Ah so you have been down this road before

Doug C :

Has the motor every been replaced?

Customer:

thats what fixed it last time

Customer:

and yes

Doug C :

How long ago was it replaced, and how many wiring failures have you had (if any) since the last blower motor?

Customer:

one sec

Customer:

ok the wires were replaced last time it went out but the motor wasnt

Doug C :

Thanks.
Did you perform the replacement yourself (or more to the point, do you feel comfortable removing the blower motor)?

Customer:

yes i can pull it out

Customer:

but my dad did it last time

Doug C :

THanks.
I would like to have you pull the motor out again and using some spare wire hook it directly to 12v/ground (you can use your cars battery) and make sure the fan has not failed

Doug C :

Typically these fans will survive two connector melts between failures

Customer:

which one is black

Customer:

or does it matter

Doug C :

Just a moment I'll check

Doug C :

Not terribly for testing, but we'll do it right

Doug C :

| -- | is black/white -- is black

Customer:

k gimme 10

Customer:

brb

Doug C :

No problem

Customer:

im back fan works fine

Customer:

wires are burnt up

Doug C :

Great

Customer:

do you know why they keep burnin up?

Doug C :

Just to be clear, when the fan was in the car, there was no activity on any speeds, even high correct?

Customer:

none

Doug C :

Thanks

Doug C :

Poor orientation of the terminals, caused excess heat, excess heat led to corrosion/oxidizing etc. They were changed to a new design a year later

Doug C :

Okay do you have a multimeter or test light?

Customer:

neither at the moment

Doug C :

Ok.....

Doug C :

Essentially there are three things we need to consider here

Doug C :

We know the fan is good. We need to verify that there is voltage reaching the blower fan... we can assume this is okay if you checked the proper fuses, but I still like to test on the connector

Doug C :

Second we would want to double check the connector condition, making sure there is no fresh melting/damage to it as this will create a high resistance point and fail the fan. Last we would want to check for ground activation formt he resistor/transistor

Doug C :

If you have the base AC the last one is not necessary as "high" speed bypasses the resistor. If you have an upper model AC however we would need to check this as well.

Customer:

whats the difference in the two ill let you know which one i have

Doug C :

Since we do not have a test light or meter right now, just for fun lets plug the motor back in (you don't need to install it, just plug it in) and check operation again while wiggling the connector. This show a weakness in the connector or a possible stuck brush that has come loose during removal.

Customer:

k

Doug C :

If you have "degrees" listed on your temperature knob, you have an upper model, I believe (I'm going to have to double check this) if you have no degrees but you do have three vertical buttons on the control panel you have the mid range, and if you have just three plain knobs and a recirc/defog button in a row (temp-recirc-fan-defog-mode) you have the base system

Customer:

base'

Doug C :

I'm sorry I have that backwards I believe just one second

Doug C :

Sorry about that, which one of these do you have?

Customer:

middle type

Doug C :

Okay the middle type will require testing for the transistor, as it is not bypassed on High

Doug C :

we still have a way around that though if necessary

Customer:

just got done wiglin wires with no luck thin ima have to re wire pretty hih up in the dash i found where my dad used a splice connectore instead of doin it the riht way

Customer:

wires are supposed to be whit n there brown

Doug C :

My primary concerns regarding wiggling the connector is right at the blower, not where the wiring is patched in... just to make sure the new connector is not failing too

Customer:

that what i did with no luck he changed those wires out last summer

Doug C :

No problem

Doug C :

Odds are we are just looking at a blown transistor if your fuses all checked out okay.
Without a a test light or meter, we are going to have to get a little creative with the testing here... we can do this, it is not the ideal method though... proper tools would be best

Customer:

im in louisiana if its improbable and danerous but probably wont work i may have tried it before

Doug C :

haha

Doug C :

So challenge accepted is what you're saying?

Customer:

it improbably improbable yea lets do it

Doug C :

Since we know the blower motor works on it's own, we need to see if it is dropping votlage (bad fuse, bad relay) or dropping ground (bad transistor, bad AC ecu).

Without a meter or test light, the only way to do this is going to be to supplement them instead

Doug C :

What we want to do is leave the blower motor out, but plugged in... this way you can get easy access tot he connector

Customer:

k

Doug C :

Using a piece of scrap wire, we want to supplement a ground to the motor, expecting the transistor or ac ecu to be not supplying ground.

Doug C :

To do this, we will take a piece of wire and back feed it into the blower fan connector on the -- terminal ( |-- ) then attach it to ground briefly (you can use the door check bolts in the door jam

Doug C :

MAKE SURE you attach it to the -- pin and NOT the | pin. If you attach it to the | pin you will blow the fuse

Doug C :

Just tap it to ground to see if the motor surges, no need to toss a lot of air around..... and make sure the key is on and fan switch is on

Customer:

o yea i forgot to tell you the motor is labelled -,+

Customer:

lol

Doug C :

I never noticed that

Customer:

but ok

Doug C :

Is it aftermarket?

Customer:

i did an i remembered last time foolin with this upside down hangin out the car we couldnt figure out which one was black or red so i seen that there made me lauh but its the one that came with the car we bougght with 43,000 miles

Doug C :

Ah

Customer:

can the wires et bad enouh not to have a chare?

Customer:

charge*

Doug C :

Yes, but usually you will see this when looking at the connector, there will be obvious damage.

Did you try applying ground like I described already? Was there no result?

Customer:

yep i had my brother heelp me so i know the ground was good the connector is not melted

Customer:

tryed wilin the other wire too

Doug C :

Okay that is a OK thing, that means the ground side is -probably- OK and we have a power supply issue

Customer:

wiggling

Doug C :

Lets double check your main blower fuse

Customer:

and then i went back and pulled every fuse out and checked it none of them were blow

Doug C :

In the drivers end cap there will be two large green fuses just outside of the main fuse area, these are both 30A fuses, check these fuses visually by removing them (specifically #6)

Customer:

thats the big 30 amp maxi - fuse

Customer:

yep that one is good

Customer:

both

Doug C :

Okay #20, 7.5A?

Customer:

its good

Doug C :

ok

Doug C :

We are running low on options here..... last thing to check on the power side is the relay

Doug C :

Luckily there is an easy way to do this, we can just swap the relay with another like relay.

Doug C :

I believe the blower relay should be identical to the defogger and a few others, give me just a moment to locate a diagram

Customer:

just let me know which one is the right relay

Customer:

k

Doug C :

Here we go... I'm not holding my breath on this one, but go ahead and swap the blower relay with an adjacent relay:

Full Size Image

Customer:

nothing

Customer:

i tried messing with the wires more i cut them further up and made a loner lead that did not work

Doug C :

Okay.

Are we 100% certain we had good contact when we were applying ground manually to the motor?

Customer:

100%

Doug C :

Okay. At this point we are going to need a test light or a multimeter to go any further.

Based on supplying ground manually not starting the fan, and the fan working outside the car, this points to a power supply issue. The power supply on this fan is pretty basic compared to the ground side. It has a fusible link (shared with a ton of stuff), a fuse, power delivered through the relay to the blower. Your only probable failures are blower fuse, relay, relay fuse. With all checking out OK, it would appear that there may be a wiring issue between the relay and the blower. This is fairly uncommon however. A proper test device would speed this up dramatically

Doug C :

Any possibility of borrowing a test light or meter from someone?

Customer:

be about 30 minutes i have one at my house

Doug C :

Sounds good

Customer:

k

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