Heater fan speed

[Hartless]

Have a 3710 with a factory cab. The heater fan will not increase in speed when turned to 2 and 3. It stays on low speed. Any help is appreciated. Thanks

 

[Dave_eng]

Blower speed problems often reside in the blower resistor which you access by taking off the cab roof.

I have attached a page from the WSM showing how to test the resistor.

Dave

 

[Hartless]

Thanks. Got the roof off and will test the register this weekend. Getting cold in Michigan and need the heater.

 

[Dave_eng]

Blower speed problems often reside in the blower resistor which you access by taking off the cab roof.

I have attached a page from the WSM showing how to test the resistor.
A page from parts illustration showing location of resistor.

Dave

 

[Hartless]

Got the resistor out and tested it. It tests to the specs so it is good. The fan does spin but only at 1 speed and not enough to blow enough air. Can barely feel the air thru the defroster vents. Thanks.

 

[Hartless]

Battery was low at 11.75 amps.

When started the battery tested above 14. I disconnected the power going to the blower motor and tested the volts going to the blower. All 3 speeds tested at 13.6 volts. When I disconnect the resistor the power tested on speed 3 is 13.6. Nothing at speed 1 and 2 with the resistor disconnected.

 

[eserv]

Battery was low at 11.75 amps.

When started the battery tested above 14. I disconnected the power going to the blower motor and tested the volts going to the blower. All 3 speeds tested at 13.6 volts. When I disconnect the resistor the power tested on speed 3 is 13.6. Nothing at speed 1 and 2 with the resistor disconnected.

This is the circuit diagram

 

[Dave_eng]

I have attached more info based upon eserv's wiring diagram.

It took me a little while to realize how the speed control is achieved.

In low speed, power for the blower passes through both internal resistors in the resistor.

In high speed, power bypasses the resistor completely utilizing a high speed relay controlled by the blower switch.

In medium speed, power utilizes one of two internal resistors within the main resistor and is controlled by a second medium speed relay which the blower switch turns on.

See if you can identify these two relays. It is possible the blower switch is gone but unlikely as it only switches relay trigger current.

A 5 amp fuse looks important in providing the blower switch with power to trigger both relays.

Dave

 

[Hartless]

It's the blower motor. After running a bunch of voltage and amp tests I hooked up an extra blower motor my buddy had for a duramax and it worked on all 3 speeds. Kubota wants $500 for the blower motor. I am calling a shop to see if they can clean it and put new bushings in it. If not, I am buying one online for $35 that is close to fitting and will make it work.Thanks for helping out with diagnosing the problem. I appreciate it.

 

[Dave_eng]

Thanks for the update.

Weird problem for a newer machine.

Dave

 

[D2Cat]

Dave, I appreciate all the help you offer folks with their electrical problems. I read them all and try to learn. I have to read it (usually more than once), and then physically do it to really get electrical stuff in my head!

I'm a slow learner, but your diagrams and input really helps. Thanks.

 

[Hartless]

Does anyone know of a replacement blower motor that may fit in place of a Kubota blower motor? Or any reason why a $35 blower motor shouldn't be used to replace the $500 Kubota with a little modification. Thanks.

Bringing mine in Monday to a shop so it can be looked at and maybe fixed but the guy said they purposely do not make replacement parts so you have to buy a new one

 

[Dave_eng]

Dave, I appreciate all the help you offer folks with their electrical problems. I read them all and try to learn. I have to read it (usually more than once), and then physically do it to really get electrical stuff in my head!

I'm a slow learner, but your diagrams and input really helps. Thanks.

Thanks. Greatly appreciate your comments D2Cat!

When writing a post, I try and remind myself of how little I knew 60 years ago and how many people helped me along the way and write accordingly. In the beginning, invisible electricity is difficult to understand for everyone.

Dave

 

[Dave_eng]

Does anyone know of a replacement blower motor that may fit in place of a Kubota blower motor? Or any reason why a $35 blower motor shouldn't be used to replace the $500 Kubota with a little modification. Thanks.

Bringing mine in Monday to a shop so it can be looked at and maybe fixed but the guy said they purposely do not make replacement parts so you have to buy a new one

Could you post a photo or two of the motor.

Dave

 

[D2Cat]

A few months ago helped a neighbor with his M9540 cooling system. He had to replace the motor on his tractor. The motor is mounted in a housing that could not be duplicated with any stock motor. Maybe your is different, but I have my doubts. Good luck and post some picture of the motor when you can. Thanks.

 

[Hartless]

I have my doubts to. Although I am not opposed to cutting a hole in the head liner to accommodate a a blower that is deeper.

 

[Hartless]

There is no housing just the motor and cage.

 

[BAP]

There is no housing just the motor and cage.

Looks similar to a heater motor used in the mid 1970’s GM trucks.