Car Blower motor variable switch design

[thenior]

Hello everyone,

I am a totally n00b when it comes to electronics, so bare with me.

I have a Buick LeSabre that has automatic temperature control. It's about 10 degrees out right now, and the blower fan works intermittently. The blower fan is ok, as well as the relay switch - it's something to do with the electronics.

Well, I don't like the automatic temperature control anyway, so I am going to directly wire the blower motor up.

Here is my diagram:

**broken link removed**

First off, I don't fully understand how pulse width modulators or relays work. From my research, this is what it seems like I needed.

I know that the blower motor is 12v, and current relay that is hooked up to it is 30amps. I don't think I can use the current relay - a fellow buick owner said that:

When the dash switch is moved to highest speed the first relay moves to a different contact. This disconnects the resistor set from the circuit and connects to the direct connection. Then a second relay allows the direct connect high speed relay to connect to the blower motor.

SUMMARY

I am trying to directly wire my 12v blower motor to my car battery, and provide variable speeds. I am totally open to other ideas, this was just my initial concept.

Here is the pulse width modulator I was going to buy: **broken link removed**

Thanks for any help anyone can provide

 

[ronv]

Fan Control

Should work.

 

[thenior]

Thanks for the reply!

Not sure on a couple things:

The other switch looking icon (not labeled SW) - is that the Fuse? or Another Switch?

What is the triangular icon at the bottom left of the diagram?

 

[ronv]

Thanks for the reply!

Not sure on a couple things:

The other switch looking icon (not labeled SW) - is that the Fuse? or Another Switch?
That is the relay contact. When the relay coil is energized the contacts close sending 12 volts to the PWM.
What is the triangular icon at the bottom left of the diagram?

The triange is ground or the negitive from the battery.
Sorry, I forgot the fuse.

 

[thenior]

The triange is ground or the negitive from the battery.
Sorry, I forgot the fuse.

It took me a while to get it... but I understand now.

So I would put the fuse between the battery and the first switch, before the circuit that goes to the load on the relay, correct (basically as close to the battery as possible)?

 

[ronv]

Yes. If you have an empty spot on the fuse block that would also work.

 

[thenior]

Sorry, here is another question!

Should the switch be after the relay? Isn't the whole point in having a relay is because it is made to handle a heavier load than a simple switch? Should it be on the other side of the relay from the battery?

 

[MikeMl]

Since the relay coil and the switch are in series, the order doesn't matter. Note that the motor (PWM module) current does not go through the switch contact, only the relay contact. Begs the question: what is the current rating of the switch? What is the maximum blower current? Is the relay even needed? Why not just get a switch which will handle the blower current?

 

[thenior]

Since the relay coil and the switch are in series, the order doesn't matter. Note that the motor (PWM module) current does not go through the switch contact, only the relay contact. Begs the question: what is the current rating of the switch? What is the maximum blower current? Is the relay even needed? Why not just get a switch which will handle the blower current?

The blower motor draws a max of 12v. The current relay in the car for the blower motor is 30A, so that would tell me it draws 30A or less.

So if I were to get something like Amazon.com: 30 Amp Off-On Rocker Switch: Automotive, it should work just fine right?

 

[carmusic]

yes it should work, but i prefer using relays for blowers and high load, i have seen a lot of high power switch melt even if current was under the specs.

 

[CRISespecialist]

try to troubleshoot first instead of connecting directly to the battery and make switch,try to replaced first the temperature switch,i am sure that parts has malfunction or defective.