Blower Motor Just Quit Working

[Flounder]

As the title says, the blower motor in my 02 just quit working the other day. I could not get the fan to turn on on any speed with the dash switch. I have checked the speed switch on the dash and it is working as it should, has not melted. Pulled the fan motor out and applied 12V of power to it and it works just fine.

I did notice that the relay cover came off and there was some corrosion on it, so I replaced it and that did not fix the problem. I put the old relay back on and when I manually make the connection, the blower turns on and adjusts to the speed that is selected.

Looking at the wiring diagram, it looks like the power for the relay goes through the blend air door motor. Should I replace that too?

What else could it be or have I missed something along the way?

 

[pbeach]

Very common. There's an enormous library of blower motor threads. Search up.

 

[Obi-Wan]

TJ blower motor resistors are notorious for going up in smoke and causing a dead blower fan.

 

[Flounder]

Very common. There's an enormous library of blower motor threads. Search up.

I have searched the many posts on here and have yet to find one that is doing what mine is doing.

 

[Flounder]

TJ blower motor resistors are notorious for going up in smoke and causing a dead blower fan.

View attachment 643651

Should have mentioned in my original post that i have already replaced this resistor, the blower motor, blend air motor, and the relay switch. Still it will not turn on. The blower fan will turn on when the relay is forced on, which tells me that the signal is not getting to the relay.

I should also mention that the blend air motor does not move or change when the selector switch is moved on the dash. Could that be part of the reason that the signal is not getting to the relay?

Thank you for helping me out.

 

[macleanflood]

Have you ohmed out the selector switch to verify functionality?

-Mac

 

[Flounder]

Have you ohmed out the selector switch to verify functionality?

-Mac

I have ohmed out the speed switch and it is working correctly. The selector switch has only 3 wires and 6 vacuum tubes on the back. The wires going to it have 12v going to it like it should.

 

[B1Toad]

I have ohmed out the speed switch and it is working correctly. The selector switch has only 3 wires and 6 vacuum tubes on the back. The wires going to it have 12v going to it like it should.

The wires on the speed switch supply the ground signal, not 12V +. If you have 12V+ at the speed switch there's a good chance you've lost the ground connection which runs from the ground point in the driver's footwell up to the mode selector switch then on to the speed switch thru the fat green wire. If the ground connection was intact, you'd see zero volts and the blower would run. Seeing 12V + indicates the circuit is open, you're seeing the voltage backfeeding from the blower motor. That same ground supply is also used to engage the AC compressor, if the AC compressor does not engage it's another clue the ground supply connection has failed.

The ground connection almost always fails at the mode switch terminal but if your isn't melted or burnt it could be in the switch or at the footwell. The ground signal gets carried thru the switch to the various modes and all the ground current for the blower also passes thru the switch and comes out on the back where the green wire carries it over to the speed switch..

 

[Flounder]

The wires on the speed switch supply the ground signal, not 12V +. If you have 12V+ at the speed switch there's a good chance you've lost the ground connection which runs from the ground point in the driver's footwell up to the mode selector switch then on to the speed switch thru the fat green wire. If the ground connection was intact, you'd see zero volts and the blower would run. Seeing 12V + indicates the circuit is open, you're seeing the voltage backfeeding from the blower motor. That same ground supply is also used to engage the AC compressor, if the AC compressor does not engage it's another clue the ground supply connection has failed.

The ground connection almost always fails at the mode switch terminal but if your isn't melted or burnt it could be in the switch or at the footwell. The ground signal gets carried thru the switch to the various modes and all the ground current for the blower also passes thru the switch and comes out on the back where the green wire carries it over to the speed switch..

Thanks for the info, but i do not have 12V at the speed switch. I have 12V at the selector switch.

 

[B1Toad]

Thanks for the info, but i do not have 12V at the speed switch. I have 12V at the selector switch.

There is no 12V supplied to the selector switch. Look at the diagram below, it is for a Jeep without AC but the blower circuit is the same. No 12V+ comes to the mode selector switch, only ground. You can see when the mode selector switch is in any position except off it supplies ground to the dark green wire on the connector C3 and feeds that ground into the speed switch thru C1, then the speed switch sends that ground thru the different resistor taps and on to the motor. The motor always has 12V+ available thru the blower relay when the key is on, it's the ground that completes the circuit thru the dash switches.

To prove it out run a temporary ground wire to the dark green wire that feeds the speed switch and see if the blower works.

 

[B1Toad]

Your blend door motor is also ground activated. The only 12V+ supplied to the HVAC control unit is for illumination, everything else is 12V-

 

[Flounder]

There is no 12V supplied to the selector switch. Look at the diagram below, it is for a Jeep without AC but the blower circuit is the same. No 12V+ comes to the mode selector switch, only ground. You can see when the mode selector switch is in any position except off it supplies ground to the dark green wire on the connector C3 and feeds that ground into the speed switch thru C1, then the speed switch sends that ground thru the different resistor taps and on to the motor. The motor always has 12V+ available thru the blower relay when the key is on, it's the ground that completes the circuit thru the dash switches.

To prove it out run a temporary ground wire to the dark green wire that feeds the speed switch and see if the blower works.

View attachment 643734

Thanks for the detailed description and clear explanation. Perhaps I was not very clear at the start. The relay is not getting power to engage and send power to the fan motor. I have forced the relay on and the fan turns on and the speed switch works. However, the relay will not engage unless I am physically forcing it to. Where does the power to engage the relay come from?

 

[B1Toad]

I saw that but what's confusing is the 12V+ at the selector switch which indicates the relay is closed and sending 12V thru the motor and back feeding on an open ground. Sometimes things get confused though on a forum and testing isn't always consistent.

The power to close the blower relay comes from a 10 amp fuse, number 8 in the fuse block. In the diagram below, which is for a 2000, the wire is red and dark green. It branches off to the relay and to the blend switch. It looks like there is 12V+ at the blend switch so I was mistaken that the only 12V+ was illumination, but I know there is no 12V+ supplied to the mode selector or the speed switch.

If you go to our resource section you will find your 2002 service manual complete with wiring diagrams. I haven't checked but I am 99% sure the 2002 will be identical to the 2000 below.

 

[B1Toad]

Here's the 2002. You can find locations of all your connectors and splice points in the W8 wiring section. The wiring looks the same although they didn't show the details of where the relay trigger comes into and out of C205, you have to scroll down to another page.

 

[dbbd1]

Thanks for the detailed description and clear explanation. Perhaps I was not very clear at the start. The relay is not getting power to engage and send power to the fan motor. I have forced the relay on and the fan turns on and the speed switch works. However, the relay will not engage unless I am physically forcing it to. Where does the power to engage the relay come from?

Can you "force" the relay, as you say, and change the speed with the climate control?

Check the coil side of the relay socket for +12v ignition-switched at one and ground at the other.

Have you checked and replaced fuse #8?

 

[CharlesHS]

Since the blower motor relay and blend door get power from the 10A Fuse 8 and the blower motor started when you manually "forced" the blower motor relay into the relay receptacle have you checked the relay wiring going into the receptacle. IF you can get the motor to run forcing the relay into the receptacle that tells me there is either loose or burned wiring or extremely oxidized clips inside the relay receptacle or the relay has too much resistance in the coil circuit to hold the relay energized.
It time to inspect the relay receptacle wiring and take some measurements.

 

[B1Toad]

I'm still suspecting a grounding issue. The only path for 12V+ to the mode switch is a back feed thru the motor which you would see on the outgoing terminals when the switch is off and should go to zero when the switch is on. If the blower wasn't getting 12V+ how could there be 12V+ at the mode switch?

Basically we have 2 conflicting test results, the fact that relay has to be forced on for the blower to run contradicts the fact that there is battery voltage at the mode switch. The only place that voltage can come from is the relay/motor and down thru the resistors.

 

[Flounder]

Thanks for all the advice. It ended up being the wiring going into the relay from fuse #8. It had come out and was not sending the signal to the relay to turn on. Once we replaced that section of wiring, it worked like it should. Thanks to everyone for helping diagnose this issue.

Brandon