Guests - If You want access to member only forums on HSO. You will gain access only when you sign-in or Sign-Up on HotSpotOutdoors.

It's easy - LOOK UPPER right menu.

Sign in to follow this  
Followers 0
Jeremy airjer W

Diagnosing Blower Motor Problems

6 posts in this topic

I wrote this up back in January and finally got around to moving it to the auto forum. This should help if you ever run into this problem.

The diagram is generic and loosely based on GM's setup and more specifically a Silverado. Most manufacturers have a similar setup and the only major differences would be a ground side control (instead of the switch supplying power to the resistor it would be grounding the power from the resistor if this is the case you test light would need to be connected to power to test the switch) and late model Chrysler minivans (they use a module that looks for a difference in a/c voltage from the switch)

If the blower works on high only than likely the resistor assembly is the culprit since power to the blower essentially bypasses all of the resistors and/or the resistor assembly entirely. The reason why none off the other speeds will work is that the resistor or the circuit for the speed four setting has burned out. The lower the setting the more resistance you need to drop the voltage to the blower. The first speed setting requires all four resistors to drop the voltage enough to turn the blower at its slowest speed. Speed 2 needs to turn the blower a little faster so it uses three resistors. Speed 3 uses two resistors and speed 4 uses one.

In some cases the fan will work on high and speed setting 4. The likely cause for this is the speed 3 resistor or circuit has burned out. Speed 4 still works because it doesn't use the lower speeds resistors to control the speed of the blower. If the speed 2 resistor burns out than speed 1 and 2 will not work but 3, 4 and high will continue to work. If the speed 1 resistor burns out than speeds 2, 3, 4, and high will continue to work.

This leads us to how do we know if its the resistor or the switch or the blower. If the blower works on high than we know the blower works. That leaves us with either the switch or the resistor assembly (there are many other possibilities) wich can be easily tested with a test light (or a voltmeter if you choose) The first thing to do is locate the resistor assemble. They can be behind the glove box, under the dash close to the blower motor or under the hood, again usually close to the blower motor. It will typically have 5 to six wires going to it. We'll start by unplugging the connector, turning the key on and connecting your test light to ground.

1.Turn the switch to high and backprope all the wires. Two of them should illuminate the test light. In the diagram below this would be wire E & F. If you don't have a digram then hold the test light on one of the two wires and move the switch to another speed setting. the wire that continuously illuminates the test light regardless of the switch position will be the constant power for high blower speed and will not need to be rechecked in the following steps.

2. Turn the switch to the next lowest setting. Backprobe the remaining wires to see if one of them illuminates the test light. Repeat until you have checked all of the speed settings.

3. If the test light has illuminated a different wire for each setting then we can reasonably assume that the switch is functioning as intended and the source of the problem is the blower resistor.

4. If you find one or more settings (but not all the settings) on the switch that does not illuminate the test light on any wire than we can reasonably assume that the switch has failed.

There are a few other things that can cause blower motors not to work as intended. The switch or the resistor assembly are the two most common problems.

resistordiagram-1.jpg

Share this post


Link to post
Share on other sites

I installed a new resistor (98 plymouth breeze) and it cured the problem for approx 10 minutes and now the fan only works on high again. I assume that the blower motor is pulling too much load and this caused the resistor to burn out again? Or is it possible I got a "bad" new resistor? Thanks in advance.

CnE

Share this post


Link to post
Share on other sites

The resistors go bad for a reason, they overheat due to to much of a draw from the blower motor. Replace the blower motor and another resistor.

Share this post


Link to post
Share on other sites

The breeze is a ground side control systym. This means that the power goes through the blower first. The resistors and the switch are on the ground side. The only current that the resistor sees is what is necessary to get through the resistor. Its hard to explain in words.

This is a tuff call. If the part was O.E. I would be a little concerned that there may be another problem. If it where aftermarket I would lean towards it possibly being defective. If it where a customers car I wouldn't have any problem trying another.

Share this post


Link to post
Share on other sites

Go figure, I read this post yesterday and after work, my blower motor is not blowing on any speed. It has to happen on one of the coldest days.

I have a Linc. Town car as my shooter and it has auto temp control. I figured it was a blower motor or the ATC head. Well a little Cub parking lot diag. and I got it fixed for now. I searched and found the elec. motor housing cover for the blower motor and banged on it once with a quick square I had in my trunk. Started blowing right away! At least I know it’s a blower motor and not ATC head. Plus the blower motor is located under the hood by the fire wall and is very easy to get at. Some are behind the glove box area.

Had to share this, because I have not had a blower motor go out in one of my Veh. in many years, but after reading this thread and with in minutes, mine was failed.

Also figure I would share this , because it could get you some heat for the ride home from work and help a person figure out what is wrong. Just give the blower motor a rap and it will buy you some time. What happens is the brush's stick because or wear or somthing. The bang free's them up for a short period of time, before they stick again, that or something sticking inside of the blower motor. The blower motor will have to be replaced as soon as you can.

Good luck!!!

Share this post


Link to post
Share on other sites

LOL, Glad I could help!!!! \:D

Good point about tapping on the blower if it does not work at all. There have been many blower motors diagnosed with a good tap by this guy!!

Another thing I was going to mention is that If any of you are looking for diagrams or specific repair info head to your local library. Many libraries offer ALLDATA for free. ALLDATA is on of the two (Mitchell is the other) main automotive resources for independent shops.

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  
Followers 0



  • Posts

    • Another disaster. I tried making relatively safe picks, and bombed. I have gone from the top 60 after two events all the way down to just over the 90th percentile. I need to just go with my gut
    • that is what we were thinking too.
    • Live link.   http://www.dnr.state.mn.us/features/webcams/falconcam/index.html      


    • BEFORE BEGINNING

      Before you begin, make sure you have a good strong battery and make sure it's charged up. If you have a bad or weak battery, you may want to replace it because if it doesn't crank good and strong, you are likely to get a low, inaccurate reading. Make sure your engine is warmed up to operating temperature(if possible). About 10 minutes of riding should do.

      First, take out the spark plug and thread in the adapter for the compression tester. Make sure you have the correct size adapter for your particular ATV. Slide your kill switch to the "off" position. Some ATVs won't crank over with the kill switch in the "off" position, so if yours is like this, then you will need to either unhook your ignition coil or ground the end of the spark plug wire to a good ground. You can use a jumper wire with alligator clips on each end to ground it. Next, make sure the throttle is in the wide open position. You can either hold the throttle lever with your thumb or you may be able to tape it or use a zip tie to fasten it to your handlebars to hold it in the wide open position. If you don't have the throttle in the wide open position, you will probably get too low of a reading. Also, if you are testing a newly rebuilt engine, the engine needs to have been run for, at least, 30 or 40 minutes or you will probably get too low of a reading.

      NOTE: Before you begin with the actual test, make sure the threaded adapter is screwed in good and isn't leaking any air out around it.

      ACTUAL TESTING

      With the throttle in the wide open position, push the start button and crank the engine over until the hand on the gauge stops moving. Each time the engine turns over the hand should raise a little more until it reaches the maximum compression of the engine. When it stops, that is your compression reading. This usually takes no more than 10 seconds. Try to avoid cranking an engine for more than 10 seconds at a time as this is hard on the starter and the battery. Now, push the relief valve on your compression gauge and that will reset the hand back to zero. It's a good ideal to repeat the test a couple or three times to make sure you get an accurate reading. On kick start models, it will be the same procedure, but obviously you will be kicking it over instead of using a start button. Worn piston rings and cylinder walls will increase the number of strokes it takes to reach the maximum reading. If you're kicking, it could possibly take as many as 10-20 kicks to get the highest reading.

      THE READING

      You will need to check your repair manual for your particular model for the correct compression specifications. See note below. Usually, an engine will run OK if it has at least 100 PSI of compression. Most engines will have somewhere between 100-250 and some as high as 300 PSI, depending on the engine. Sometimes they will run with under 100 PSI, but usually not very well. If you get a low reading, you can do a "wet test" to try to help determine the problem.

      If your reading is too high, then you probably have carbon built up on your piston and combustion chamber.

      NOTE: You may get a low reading on some engines because some engines have a decompressor assembly built into the camshaft. Check the service manual for your quad to see whether or not your quad has a decompressor assembly built into the cam.

      WET TEST

      If you got a low reading, pour about 1-2 teaspoons of clean motor oil down into the cylinder through the spark plug hole and do the compression test again. If your reading increases, then your rings or cylinder walls are probably worn. If your reading doesn't increase, then it's probably your valves. You could have a bent valve, you may have leaky valve seats, or your valve clearance may not be adjusted properly. Also, low compression can be caused by a blown head gasket.

      CAUSES OF LOW COMPRESSION

      *Worn piston rings or worn or damaged cylinder walls
      *Leaking valves
      *Valve clearance not properly set
      *Blown head gasket

      CAUSE OF HIGH COMPRESSION (stock engines)

      *Carbon buildup in combustion chamber and on piston

      NOTE: Compression testing is a good way to keep track or "gauge" the wear in your engine. When you first get your ATV or when you rebuild the engine in your ATV, you can do a compression test and then later on, you can do them periodically. This will help you determine the wear in your engine each time you do a compression test and will guide you in knowing when your engine needs rebuilding.

      This is about all I can think of. I hope I didn't leave anything out and I hope this helps everyone with their compression tests.
    • As dumb as this sounds how is this done?
    • Try a compression check. And make sure the choke is opening all the way.
    • They are not the best out their but for the price and your average person not too bad I guess, Its going to send lead to where its pointed. This is probably what is going to happen he is going to buy a package shoot it for awhile then start upgrading everything to how he wants it and it is going to end up costing way more than if he just built one himself how he wants it.  
    • Hello, well I convinced my brother in-law to pick up my buddies old 1980 185 although pretty sure he said it was bored out to a 200? Here is the deal it's been sitting for a solid 8 years. I know it ran fine before. Not the delema-----   It starts right up (he bought a new carb odd amazon) although it sounds like a jet with high rpms. Looked at the throttle cable that's fine. Floats are fine. So he plugged this hole in the air filter and got it to idle down although when he hit the gas wouldn't get any power. Read a few things online and they tell you to just bypass the filter box and all that so back to amazon we went to get one of those filters that mount right up to the carb and it's still the same issue..   I just haven't seen anything like this? Do you guys have any thoughts or tricks that we/he could try?! Thanks in advance
    • Hi Everyone,  I'm looking into buying my first true fish finder and I'm a little perplex with the mapping card situation.  I'm looking at Humminbird Helix 5's and 7's.  I'm drawn to the autochart feature.  From my understanding, you can record 8 hours of charting onto the internal storage, but, is there any native mapping included on the unit or do I absolutely have to get some sort of mapping chip, zerolines or lake master, or navionics?  Can I store data on a blank SD card?  I've been researching this a lot and haven't found any conclusive answers. Thanks everyone!
  • Our Sponsors