Back in the threads on 12v heater fan motors I posted the NAPA heater fan rheostat that I used. I was driving around yesterday morning and had the fan on about 20% (which means the resistor is dropping a fair amount of the 12v) for about 1/2 hour. I got too warm so I went to turn it off; the **** was so hot it was nearly melted! It wouldn't turn the shaft, it was so soft. Got a nice burn...

I hereby withdraw my endorsement of this POS. Or maybe it would be OK if a dropping resistor was added in front of it. I may install the GM-type coils that mount in the fan housing (see BobbyTNM's post back then).

 

Ah crap! I was the one who brought that thread up way back when. I bought the 6 volt version but have yet to get it hooked up. Thanks for the warning.

Shane

 

It "may" be OK for 6v. It has gotten plenty warm before, but not this hot.

 

Thanks for the heads up, Ross. I was planning on using that switch, but it looks like I'll be coming up with a different plan. This is probably why all the OE's mount their dropping resistors in the heater plenum. They are in airflow that way to help keep them cool.

 

Or use them "wide open". Here in the cooler climes, I noticed the heat thing and have just made it a point to use it only on HIGH.

With any resistor/reducer, the lower the setting - the higher the resistance - the more heat is created.

 

That's an option MT but my heater really puts out the heat! It can get plenty cold here too but it quickly gets stuffy. I do have a water control valve, and need to hook it up.

BOR, yes you're right, plus the heat they give off is useful.

 

Heaters? you guys have heaters??

Thats a bummer Ross

Bobby

 

Yeah, but we don't have to mess with AC!

 

Joe, if you need any heater switch assistance CALL ME!! haha

 

yup, i use the same pos. can get VERY warm. never got hot enough to soften plastic. have had on for hours at a time. guess i just got lucky. keep us posted on what you use as replacement.

 

As I recall, you've replaced your heater motor with a 12 volt version. Could be the motor you used requires more watts to turn (or turns at a higher rpm) and the extra draw could be causing the excess draw attempt (that the rheostat tries to step down at lower rpm) to over heat. Wouldn't take very much at all to put a rheostatic switch over the top.

Another stupid question though: since these are available in both 12 volt and 6 volt versions, are you sure you have the 12 volt and not the 6 volt version? If you told the guys at NAPA it's for your 52 they may have looked at th ecomputer and slipped you a 6 volt switch. Just thinking out loud.

 

even the OEM 6v switch with the resister coil hanging off the back in my '53 F250 gets plenty darn toasty when run on low. doesn't take long for it to heat up enough to give ya a good burn. i wish there was a simple way to pull the fan motor and squirrel cage without having to pull the heater core too as mine makes more noise than air at the moment.

 

DL, depending which exact heater you have, you don't lose but a few drops of coolant pulling these heaters, because the hoses enter/leave the core higher than the engine. It doesn't get any easier.

Julie, I got it after I converted to 12v, so it's the right piece. I always look up the P/N online and just tell them I want that.

I have some massive dropping resistors I scarfed up cheap, they are used on Porsches to give variable radiator fan speeds. I'm going to see if putting one in series gives me a better range and less heat in the switch.

Porsche 924 924S 944 Radiator Cooling Fan Resistor: eBay Motors (item 280583133708 end time Nov-07-10 16:08:39 PST)

 

Good point!!

 

Howdy,


Yeah. Using a dropping resistor is a terrible way to do it. Simple? yes. But they do get hot if you don't size the resistor for the power it will have to dissipate. Or provide a suitable heat sink or air source to cool it.


You'll have the same problem with the instrument dimmer too depending on how many instrument lights, radio lights etc you have.

My plan is to use a solid state PWM motor speed controller for my heater.

The advantage is that it will provide full voltage to the motor and will not get hot when you crank it back! The following links explain what PWM means if anyone is interested.....

I haven't measured the max current my heater motor draws but I am assuming it's less than 15 A or so.

The following controller should work for that.

They have a kit model which I would build myself. The one below is the assembled and tested model for a little bit more.

MX033 - DC PWM Motor Speed Controller 15 Amp - Assembled & Tested

I'll measure my heater motor at max "draw" and if it's more than 15A I'll get the 30A model. It's only about $30.

MX066 - DC PWM Motor Speed Controller - Assembled & Tested


This type of DC motor speed control is exactly the same way a cordless electric drill motor is controlled. It would be extremely inefficient to use a dropping resistor in a battery operated device because of the energy loss due to the resistor.

Not only would it get hot, but that heat is also lost power that could be used to run the drill longer.... Your battery would go dead MUCH faster since it's also heating the resistor. You also would get a voltage drop at the drive motor resulting in a loss of torque and motor efficiency.

These type of circuits are also extensively used in model cars and electric trains etc....


Here's another one that is good for about 15A but I like the ones above better...

http://www.virtualvillage.com/12v-15..._medium=shcomp



Cheers,


Rick