My LS400 seems to be having the same weird blower motor issues as some others around here. I can't find a replacement Blower Motor Resistor online anywhere. Does the 1997 LS have one? Does it use PWM or something else? Does anyone have a part number?

 

It uses PWM and the part number is 87165-50010 or 87165-50020. Both can be used but a new part is discontinued and no longer available.One idea is to find a used one.

In stead, a skilled guy would use a 87165-22040 or 87165-22050 after the big modification. Attached photo shows the inside of 87165-22040 (left) and 87165-22050(right).

These two are for latter models with the circuit simplified using a custom IC. 87165-22040 (left) has some noise problem and 87165-22050 (right) has leaking capacitor problem due to the liquid contains the QAS.

A PWM has good merits such as a lower power dissipation and a smaller size but the switching noise is often heard.

 

Hey, I am having the same issue, blower going out and it's hard to find a replacement 87165-50010/20 module.

It would be nice to be able to mount the newer modules.

1) Is there a bracket or adapter plate available?
2) Can you use the 98+ blower boxes as a drop-in replacement?

Thanks

 

I don't think any bracket or adapter plate is available on the market. A skilled guy would use a 98-00 module instead of a 95-97 module seeing these 2 diagrams below with a DIY work. Luckily connector's pin assignment is the same but module is mechanically different and this has to be dealt with paying an attention on a heat dissipation. The module dissipates some big heat due to the switching loss of the PWM, you know. This thread may be also useful for you.

 

Thanks for that.

In testing I've found that the newer fan speed controller works fine. The harness that it uses will plug right into the fan and the plug on the blower box.

The newer controller will not mount to the blower box - the heatsink and mounting tabs are completely different. An adapter could probably be designed and 3d printed.

I ordered a 98+ blower box, and they are largely similar except for the controller mount and the blend door motor. It looks like the bottom portion of the box will swap over.

Unfortunately the blower box I received to try and transplant was damaged, so it would be difficult to use.

So far though, it looks like the 98+ blower box is very similar to the UFC95-97, and swapping the bottom of the box looks to allow use of the newer and more abundant 87165-22050 or 87165-22040 controllers. I'll find out for sure when I get a unit that hasn't been thrown around.

 

[QUOTE=Yamae;11873524]The module dissipates some big heat due to the switching loss of the PWM, you know. This thread may be also useful for you.

Took a minute to go back and re-read this. The heat you mention, would come from the control module for either the old or newer design, correct? The wiring looks simple enough and the control signal seems to be the same between the 2 since it worked to control the blower.

When I hooked up the newer controller, it controlled the blower as expected but I did not run it long enough to see how hot it got.

Is there any additional heat when using the newer module on the older chassis than what is normally generated by the module? My understanding is that the heat would be handled by mounting the controller properly, with the heatsink in the blower box as designed.

 

The heat is the result of the switching loss of the PWM as is explained here. Your understanding about the heat is correct. Mounting the controller properly makes it mostly possible to work the unit well. Without mounting the unit and if the unit is floating in the air, the unit will become very hot and it may be damaged.

The waveform below shows the switching ratio when the fan speed is set to the lowest on my 98 Celsior. As you see, the rise time is about 0.1msec and the fall time 0.07msec. These 2 and the internal resistance of the MOS-FET cause some heat and it has to be dissipated well attaching the unit to the fan block body. The unit is mechanically different and you need to make and use an adapter plate using a good heat conductive material such as a copper or an aluminum.

 

I think I'd better to add some. The unit 87165-22040 used to have switching noise problem and newly 87165-22050 has released quickly and it showed lesser noise level but those brown capacitors are QAS capacitors and they may leak someday.

The noise is coming from those electrolytic capacitors used. Those work like a mini speaker somewhat. A big PWM switching power is enough to make capacitors to radiate the switching sound as if those work like a speaker. To reduce the noise level, the unit is redesigned and additional glue was used. That's the reason why 87165-22050's capacitors are surrounded by the white glue to damp the sound.

 

Thanks for the details. I installed a 98+ airbox with the newer model blower controller into my 97.

The only physical difference between the blower boxes are the blower control module mounting. The recirculation motor is different on the newer box, but the mounts are there for the old style motor and it carried right over.

So far so good, it controls the same as the original and doesn't seem to overheat. I have my blower back and it's not tied to the old control module (87165-50010)

Either 87165-22040 or 87165-22050 would work now.

 

Thanks for the update. I'm glad that you succeeded to use the controller which was designed and made for newer models.

 

So, you took the lower half of the blower box that holds the motor and it fits to the upper half the holds the blend door controls without modification? Just screws right on?

 

I was able to swap the entire 98+ blower box over. The blend door / recirc motor needs to be swapped over though.

 

Thanks, Man! Summer is coming and I need that AC!

 

Hi Scodge, Will you do us a favor?
When you do, it would be nice to take photos and show us here. There will be many people who will have problem not able to obtain the old blower motor controller. Your photos will help those who suffer the problem.

 

Sure.