Blower motor not working

[B1Toad]

Pulled some archives of the JP Magazine article I mentioned before...

Most of the pics didn't survive on the wayback machine but gives you an idea of how this was being address in the DIY community all the way back to 2007.

https://web.archive.org/web/2015012...w-to/electrical/154-0710-jeep-fire-prevention

https://web.archive.org/web/2012100...les/electrical/154_0710_jeep_fire_prevention/

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Basically - cut the wires behind the switch in the dash and have them activate/trigger the relays. Then run key-activated 12V (I think I pulled mine from the cigar lighter) to be the 12V that is the source that then goes to the blower motor.

This keeps the motor from drawing extra current through the switch as it wears out and peaks it's current draw on on the lowest setting (which melts the HVAC switch in the dash).

The blower motor resistor pack still remains a 'fuse' in the system — but that's cheaper than the HVAC switch panel...

Thanks, good article. I don't understand what you mean by "peaks it's current draw on on the lowest setting" though, Why would current draw be higher on low? What I do see on the switch is that the 2 lowest speeds have #16 wire, while med-II has 14 and hi has 12.

On mine I added a second relay to the high speed, I already had one bypassing the mode switch. If one was to do all 4 relays there would be no need to bypass the mode switch though. Interesting.

 

[FarFire70]

Thanks, good article. I don't understand what you mean by "peaks it's current draw on on the lowest setting" though, Why would current draw be higher on low? What I do see on the switch is that the 2 lowest speeds have #16 wire, while med-II has 14 and hi has 12.

On mine I added a second relay to the high speed, I already had one bypassing the mode switch. If one was to do all 4 relays there would be no need to bypass the mode switch though. Interesting.

The blower motor draws/pulls a constant power to operate.

The blower motor resistor has a constant resistor value at each blower motor speed. Highest resistor value at low speed to provide less current to the motor to slow it down.

Power draw of the motor increases with age as the bearings wear out.

As the blower motor needs more power — the lowest setting adds the highest resistance in line of the motor. So the current increases to keep the power the same at the motor.

 

[FarFire70]

On mine I added a second relay to the high speed, I already had one bypassing the mode switch. If one was to do all 4 relays there would be no need to bypass the mode switch though. Interesting.

You've done the opposite needed. High power setting is already a basic straight shot from the battery to the motor due to low resistance in the blower motor resistor.

Lowest setting is where the highest current is created and causes melting of the blower motor resistor, switch, wiring, or all these

 

[FarFire70]

Not a perfect analogy but, in the OEM design without wear:

If you have a garden hose pointed at a pinwheel...

Pinch it with your fingers to minimize water - that's the lowest setting.

The more you open your fingers, the faster the pinwheel spins.

High speed - let your fingers off the hose.

—-

Now add a dime on one of the pinwheel flares. Causing increased drag.

Its will need more water to spin at the lowest speed you had before.

It will require more at the middle and higher settings than before —- but that first movement draws the most.

 

[B1Toad]

I totally understand that a motor draws more current when the load increases, that is a given on any inductive load. But we have fixed resistors on 3 of the speeds to control the speed, so on the 3 lower speeds the circuit is resistive-inductive. The resistor drops the voltage which in turn limits the current. This is proportional to the amount of resistance, so the more resistance, the more current gets limited. (We know that current is limited through the resistor because if it wasn't, the motor would simply draw enough current to maintain it's rated speed and the resistor would not slow it down). So I don't see how the lowest setting, with the most resistance, would proportionally draw more current than any other speed that is controlled by a resistor. One could argue that the high speed circuit, being basically all inductive, would be more likely to experience runaway current when overloaded as there is no fixed resistor in place to limit it.

The other issue I have a problem with is why aren't we seeing low speed meltdowns? Granted I have only seen 6 meltdowns but they have all been the high speed. 3 were Ford vans in a fleet where the high speed terminal on all 3 dash switches melted, 1 was on my 1987 Mercedes 300 where the high speed fuse melted repeatedly, 1 was my Jeep where the input terminal to the mode switch (where all the negative current passes) melted when the blower was on high. The 6th one is the one in this thread, which was the high speed terminal on the blower switch.

I'm not discounting your theory and this is an interesting discussion which I plan to research more. Do you have any examples of low speed meltdowns, or any references to your theory?

 

[FarFire70]

I'm not discounting your theory and this is an interesting discussion which I plan to research more. Do you have any examples of low speed meltdowns, or any references to your theory?

Personal experience. Replaced blower motor resistor twice over the life of the Jeep (150k miles) - both times were after the lowest setting stopped working. Resistor showed burnt damage.

I'd rather the resistor is the fuse vs the switch. But, when it isn't, the switches melts - and examples have been on lowest setting most typically (but this is more anecdotal vs my own experiences).

 

[FarFire70]

Personal experience. Replaced blower motor resistor twice over the life of the Jeep (150k miles) - both times were after the lowest setting stopped working. Resistor showed burnt damage.

I'd rather the resistor is the fuse vs the switch. But, when it isn't, the switches melts - and examples have been on lowest setting most typically (but this is more anecdotal vs my own experiences).

For reference, here's my four relays installed in the dash.

They're obviously pulled out for this picture. But, it shows you can fit four relays within the dash for each four settings of the blower motor.

 

[01saharatj]

Thanks, good article. I don't understand what you mean by "peaks it's current draw on on the lowest setting" though, Why would current draw be higher on low? What I do see on the switch is that the 2 lowest speeds have #16 wire, while med-II has 14 and hi has 12.

On mine I added a second relay to the high speed, I already had one bypassing the mode switch. If one was to do all 4 relays there would be no need to bypass the mode switch though. Interesting.

So from the relay there is a smaller yellow wire and a white wire. Wich one Igor’s to positive power and which one goes to ground?

 

[B1Toad]

So from the relay there is a smaller yellow wire and a white wire. Wich one Igor’s to positive power and which one goes to ground?

On the pigtail socket I bought terminal 86 happens to be white. Since standard practice is to put power to 86 I put it to the lighter power and since 85 is ground and the control on our HCAC uses ground the relay gets triggered by ground. Colors may vary on different pigtails, and although putting ground to 85 and hot to 86 is common practice, in reality the relay will work either way unless it happens to be a metal one with a grounded case.

 

[B1Toad]

For reference, here's my four relays installed in the dash.

View attachment 555233

They're obviously pulled out for this picture. But, it shows you can fit four relays within the dash for each four settings of the blower motor.

I'm seriously considering replacing the ageing blower motor which seems to be the root of the whole issue.

 

[01saharatj]

On the pigtail socket I bought terminal 86 happens to be white. Since standard practice is to put power to 86 I put it to the lighter power and since 85 is ground and the control on our HCAC uses ground the relay gets triggered by ground. Colors may vary on different pigtails, and although putting ground to 85 and hot to 86 is common practice, in reality the relay will work either way unless it happens to be a metal one with a grounded case.

I went ahead and ordered a new blower fan and resistor.

***** But one thing I need to know is where all the grounds are landed and I need to check to see if they are grounded properly or wire broken etc…****any help with this would be appreciated

 

[B1Toad]

It all comes from ground point 202 in the left footwell as a #12 wire that attaches to the small terminal on the 3 port connector of the mode switch. Where are you getting your new parts?

 

[01saharatj]

It all comes from ground point 202 in the left footwell as a #12 wire that attaches to the small terminal on the 3 port connector of the mode switch. Where are you getting your new parts?

Amazon

 

[01saharatj]

Amazon

When you say left footwell is that the drivers side footwell like by the pedals?

 

[B1Toad]

When you say left footwell is that the drivers side footwell like by the pedals?

This is the view as if you were standing in front of your Jeep, G202 is sort of up in the side of the kick panel if you stick your head down by the pedals and look up and to the left. It's a bit awkward to work on, I can only get one hand in there.

 

[01saharatj]

Is this the blend door actuator?

Hey thanks for the above diagram that helps tremendously

 

[01saharatj]

This is the view as if you were standing in front of your Jeep, G202 is sort of up in the side of the kick panel if you stick your head down by the pedals and look up and to the left. It's a bit awkward to work on, I can only get one hand in there.

View attachment 555692

There is nothing grounded on mine according to the diagram that isn’t what’s on mine look at my pics.

 

[01saharatj]

Does anyone know where the blower motor relay is located? Please!

 

[B1Toad]

You should have a ground point on the driver's side, G-302 and 303. On the passenger side you should have G202 and 203 in the same location as it is on the drivers side. Looks like your ground comes from the pass side but when I ran my new ground I used G302 on the driver's side.

 

[B1Toad]

There is a 2001 service manual in the resources section that shows all of this, but it's hard to navigate because it's not hyperlinked. The 2000 manual is mostly if not exactly the same as for the 2001 and it is hyperlinked and much easier to navigate.