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Resistor

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where can i get a blower motor resistor for a 87 superliner. dealer says no got! man I have a lot of trouble trying to get the simple things for this truck :pat:

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where can i get a blower motor resistor for a 87 superliner. dealer says no got! man I have a lot of trouble trying to get the simple things for this truck :pat:

The resistor part number for the RW in this post: http://www.bigmacktrucks.com/index.php?showtopic=15191 is 4379-RD536470 (or at least it used to be). It was built in 1987, so I would imagine it should be the same as yours. I'll try to check on it tomorrow and see if it available or if they're just blowing smoke.

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Sounds like quite a large resistor. How many amps is a blower motor? you could size up a resistor from an electronics supply catalog. I have a few large ones lying around but they are rated for 200 watts only, and those are actually huge.

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Sounds like quite a large resistor. How many amps is a blower motor? you could size up a resistor from an electronics supply catalog. I have a few large ones lying around but they are rated for 200 watts only, and those are actually huge.

Not really too physically large. They depend on airflow through the plenum to survive. Leaves and trash buildup on the cowl inlet screens take them out quickly due to reduced airflow. As Herv stated if the blower motor is run on the "high" position of the switch, the resistor is bypassed electrically and not in the circuit.

Rob

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I am thinking a FLD freightliner may use the same one. If it ant you could rework the mount and it would. The FLD has 4 ter. on it.

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I am thinking a FLD freightliner may use the same one. If it ant you could rework the mount and it would. The FLD has 4 ter. on it.

I am going to take a pic of it and go to freightliner cause i think you is right

Thanks Rich

PS high speed does not work with this resister.

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Hey Dunny, I had a parts man check that number out, it's still a good number and it's available (literally hundreds in Mack's warehouses). He told me probably around $5.00

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Hey Dunny, I had a parts man check that number out, it's still a good number and it's available (literally hundreds in Mack's warehouses). He told me probably around $5.00

i only have 1 mack dealer here. How would i go about getting it cause my dealer says that mack does not stock it anymore

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i only have 1 mack dealer here. How would i go about getting it cause my dealer says that mack does not stock it anymore

Trey don't go to far out of his way for you too?

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Not really too physically large. They depend on airflow through the plenum to survive. Leaves and trash buildup on the cowl inlet screens take them out quickly due to reduced airflow. As Herv stated if the blower motor is run on the "high" position of the switch, the resistor is bypassed electrically and not in the circuit.

Rob

Yes I figured the resistor is used to divide the voltage for low speed. Why i said.. what i said, i have no idea, lol. For some reason I was thinking a few hundred watts but that is not the case.

You can calculate the motors resistance using the formula R=E/I meaning Resistance (in ohms) equals the voltage (E) divided by the amperage(I). So for example: if we have a blower motor that draws 10 amps you divide 12 by 10 which equals 1.2. So to divide the voltage in half you need a 1.2 Ohm resistor. And since the current (amps) will also half, the wattage will be 6 volts times 5 amps which is 30 watts. So you don't need a very large resistor at all. I don't know why i didn't think that one out.

You can easily source one from an online electronics supply company (digikey, mouser, newark) and just connect it.

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Yes I figured the resistor is used to divide the voltage for low speed. Why i said.. what i said, i have no idea, lol. For some reason I was thinking a few hundred watts but that is not the case.

You can calculate the motors resistance using the formula R=E/I meaning Resistance (in ohms) equals the voltage (E) divided by the amperage(I). So for example: if we have a blower motor that draws 10 amps you divide 12 by 10 which equals 1.2. So to divide the voltage in half you need a 1.2 Ohm resistor. And since the current (amps) will also half, the wattage will be 6 volts times 5 amps which is 30 watts. So you don't need a very large resistor at all. I don't know why i didn't think that one out.

You can easily source one from an online electronics supply company (digikey, mouser, newark) and just connect it.

Yes but a standard carbon based resistor does not release it's internal heat as readily as a ceramic case resistor does. I've seen standard plastic cased, carbon based resistors used in this application not hold up long at all.

Rob

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i only have 1 mack dealer here. How would i go about getting it cause my dealer says that mack does not stock it anymore

I don't know if it can be drop shipped to you or not. I would tell your dealer that you know better and then give them the part number you need.

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Yes but a standard carbon based resistor does not release it's internal heat as readily as a ceramic case resistor does. I've seen standard plastic cased, carbon based resistors used in this application not hold up long at all.

Rob

Yea, you would need a wire wound resistor. Either encased in ceramic or better yet, encased in an aluminum finned case to dissipate heat.

You would need allot of carbon resistors to get 30 watts and 1.2 ohms :P

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Yea, you would need a wire wound resistor. Either encased in ceramic or better yet, encased in an aluminum finned case to dissipate heat.

You would need allot of carbon resistors to get 30 watts and 1.2 ohms :P

Hey Hey, watch that fancy wordage, I am a owner operator and all my trucks are old enough to drink :wacko:

Edited by dunny

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I am going to take a pic of it and go to freightliner cause i think you is right

Thanks Rich

PS high speed does not work with this resister.

If the blower does not work on the hi speed setting, then there's something else wrong.

The resistor is not part of the circuit when the switch is in the high speed position, so therefore the problem could be in the switch, motor, wiring, circuit breaker, or it could be a bad ground.

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If the blower does not work on the hi speed setting, then there's something else wrong.

The resistor is not part of the circuit when the switch is in the high speed position, so therefore the problem could be in the switch, motor, wiring, circuit breaker, or it could be a bad ground.

there is some sort of diode on the hot side of the resistor. if i cross each end and the fan switch is on high then the fan blows your hat off :wacko:

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there is some sort of diode on the hot side of the resistor. if i cross each end and the fan switch is on high then the fan blows your hat off :wacko:

That is an "anti spiking" diode. It basically absorbs and routes the transient voltage spike to ground when the switch is operated.

Rob

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