professionalpyroman

Folks,

here is a write up of a rebuild I did on my car to get the blower fan back to working order. I replaced the power transistor for the blower fan as well as rebuilt the amp circuitry. The required components have been listed on the forum before and the link to that thread is included in the document. Again, might be applicable to your car, might not. I had my fan work intermittently and eventually not at all. I performed the repairs described in the document, and now the fan works perfectly. I started working on this car when I was a teenager, 15 years ago, and I have never known the blower to work as well as it does now. Your mileage may vary with the degree of repair needed, and your relative skill. It's a fairly easy circuit to practice on if you think you might want to repair other circuits in your car as well. Take pictures and take your time.

Matt

gsmithrx7

I have a blower malfunction where grounding the blower will allow it to run at full speed only.

I have a used transistor to swap in but I need to know how to test it so I know it is good.

This way I can also test the original transistor to make sure it is bad before I tear down the housing to replace it.
I do have a spare fan amp if the transistor is good.

This is the transistor in the heatsink, The dealer had me buy the other transistor, but found out later my blower does not use this one!
It was built at the end of 1988 using a blower unit to be used in the 1989 models!
I am new to electronics.
I bought a multi-meter. and promptly blew the fuse in it!

Hot_Dog

Refer to this YouTube video:

gsmithrx7

Thanks for the video, I will have to do some research to learn about this testing.
It is not as straight as I hoped!

professionalpyroman

I would go ahead and replace the big transistor at the motor regardless. That requires the least amount of soldering work to replace, you don't have to have as much skill to work on it. If replacing the transistor fixes your problem, great. If not, you still have a new transistor in the motor assembly and the problem will be in the little fan amp box that is soldered to the climate controls. Sometimes it's just a cold solder joint that has cracked but it can also be capacitors or diodes. Those parts are easy to find and replace on the amp board since it is a single sided circuit board.

Remember to put some thermal paste (like for a computer heatsink) on the transistor so it has a good thermal transfer to the big heatsink on the motor assembly. Take pictures and we can help if you have questions about stuff

You can get those transistors new for a buck or two apiece.

Hot_Dog

I agree with pryoman. Just replace it. I bought a couple for my S5 a few years ago. They seem to be more scarce and expensive today. Aliexpress sells them for a few bucks apiece, but they're shipped from China. I've ordered from Aliexpress before. They seem to be a reliable company. Here's their link for that transistor: https://www.aliexpress.us/item/32568...2usa4itemAdapt

professionalpyroman

There's all kinds available. Look for transistors that feature the TO-3 package design like in my picture in the write up.

Hot_Dog

Ok, I guess the mfg dictates the availability, but they all must meet the same spec. The one in pryoman's write-up is mfg'd by Onsemi p/n ON MJ11016G, and is available in the US from Digikey, Newark or Mouser Electronics. Here is a link from Digikey: https://www.digikey.com/en/products/...J11016G/919445

gsmithrx7

Thanks for all the tips, it is difficult for me understand electronic things, this will get me off in the right direction!

professionalpyroman

I found this video. These could be possible replacements, but someone would have to try it out in a heavy duty cycle of running the fan constantly during hot weather.