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fan blower motor speed control not working


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jackx
User

May 18, 2015, 2:10 PM

Post #1 of 10 (892 views)
fan blower motor speed control not working Sign In

I got a 1997 blazer. The blower fan switch does not work. It stopped working when I started
it up today but after driving it about 10 miles the fan came on. I let it run a while then
adjusted the fan speed to slow it down and it quit again.

I pulled the dash apart and I used my voltage meter to check and it is getting
power.

I checked around and I believe it can either be the switch itself or the switch
resistors that apparently are mounted under the hood in the fire wall next to
the blower motor.

How do you determine what needs to be replaced?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 18, 2015, 4:57 PM

Post #2 of 10 (880 views)
Re: fan blower motor speed control not working Sign In

Is the motor getting a ground signal?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jackx
User

May 18, 2015, 6:05 PM

Post #3 of 10 (875 views)
Re: fan blower motor speed control not working Sign In

how do I determine if its getting a ground signal


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 18, 2015, 6:08 PM

Post #4 of 10 (872 views)
Re: fan blower motor speed control not working Sign In

You can use a regular test light if you clip the wire to a power source.They make test lights that will identify either power or ground.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jackx
User

May 19, 2015, 6:57 AM

Post #5 of 10 (862 views)
Re: fan blower motor speed control not working Sign In

I checked the ground wire to the fan with a test light and the light lite up so I guess the ground is
ok.

I switched it on and the fan is working now. Its been raining everyday for a week and maybe
the humidity is causing the switch to act up.

If it does it again I will switch the horn relay with another relay and see if the fan works then.
If it does I'll get a new relay.

If that doesn't fix it I will be back because I'll need some advice as to how determine what is causing
the problem.

If I have to replace the switch I'll need advice. I looked at it and I have no idea how its
attached to the a/c switch mount housing. I do know you can buy the switch itself and you don't have
to buy the entire ac switch mount. The fan sound ok but who knows. I don't have the electrical
testing equipment to monitor the wave. I know its difficult to replace. You have to cut the plastic
housing covering it. That's the last thing I want to do.

I put some dialectic grease on the switch prongs and put the dash back together. I'm guessing if it
works for a week it will be ok for a while.

Thanks for the advice


(This post was edited by jackx on May 19, 2015, 7:19 AM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 19, 2015, 7:21 AM

Post #6 of 10 (858 views)
Re: fan blower motor speed control not working Sign In

If you want to waste a bunch of money, go ahead and use that method.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

May 19, 2015, 7:58 AM

Post #7 of 10 (852 views)
Re: fan blower motor speed control not working Sign In

Little tip.. next time the blower stops working. With the switch on high take something and smack on the blower motor. If the blower take off when you do that, you probably have a faulty blower motor.





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Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

May 19, 2015, 8:01 AM

Post #8 of 10 (850 views)
Re: fan blower motor speed control not working Sign In

Sport - where did you check for ground that tested good then this thing worked? Dielectric grease lasts AGES not days and both doesn't conduct electricity on its own plus it almost 100% waterproof - used for underwater things - hopefully not cars! To dry a wet connection of water the name sake WD-40 = Water Displacing FYI. With a wet (if that's real) connection that is fussy, one then the other to finish.


Where you checked probably pulled on a connection or ground that IS the spot? It would test OK while working of course but whatever you wish now - leave it alone as fixed as you might have or wiggle test away where you were to cause it happen and focus on that area. Now working I doubt you need a new anything,


T



jackx
User

May 19, 2015, 9:58 AM

Post #9 of 10 (843 views)
Re: fan blower motor speed control not working Sign In

 

I did exactly what Hammer time suggested I do and I don't plan to do anything more that
will cost me cash until I figure out what is broke. The only thing that may cost money will
be the switch replacement or replacing the resisters mounted in the firewall or the fan. I
won't do that unless I know they are the problem.

I think the suggestion from Descrete will be difficult but I will try it if the possible "free fix" of
swapping the relays doesn't fix the problem if the fan stops again.

The fan is covered in plastic though and I will have to carve out the plastic cover to get to the fan.
Like I said I may have to do that but its the last thing I really want to do. That plastic is old and
brittle and I fear it will all just crumble away. But what the heck you do what you have to do.

I suspect the fan motor is the culprit. In the big picture it runs all the time. the truck has
over a quarter million miles on it and its never been replaced. I'm betting if I bang on it when
its not running it will come one. If so I will know it needs to be replaced As I have said I do not
have the electrical equipment to test the wave so banging on it is the only way to determine if
its the problem.

I think I will bare the wires and test the wires to the fan first before I cut out the plastic because if
its getting the right voltage the fan should run. If its getting the voltage and not running then I will
know the fan is bad.

Thanks for you advice I will get back if I it the fan stops running again if I need more advice.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 19, 2015, 3:26 PM

Post #10 of 10 (836 views)
Re: fan blower motor speed control not working Sign In

If you actually did those tests correctly, then you don't need any switches or relays. You're eliminated everything but the motor if it's receiving power and ground.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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