24V Heater blower resistor

[FF LC FREAK]

Hi all,

Does anyone know the specs on the heater blower resistor on a 24 volt rig? I broke my resistor, and it is beyond repair. They are NLA from Toyota. On my 12 volt fj40, the resistor is a 1 ohm 50 watt resistor. I'm guessing that would be incorrect on a 24 volt system, but I'm not sure. So, does anyone know the specs? Or, do you know where I could get one? I don't mind sourcing a new resistor, but I need to know what to get.

Thanks!

 

[Chris Wilcox]

Post a picture of where it is on the truck and I will go measure it for you. At least on A hj60 24V truck.
Send me a PM also when you do this since I don't check this subforum often.
Chris

 

[FF LC FREAK]

Here's a pic. Sorry for the poor quality. Its the resistor on the blower motor:

After a closer look, I see a 4 ohm symbol on it. So, that solves half the equation. Now, I just need to know how many watts. Anyone got an idea?

 

[Chris Wilcox]

Is that a BJ40/42. The 60 series is much different in that there are more than one resistor and it is probably in the airflow. I'll go have a look.
For the wattage, could you use the fuse rating x voltage to bracket the upper end of it?
Chris

 

[langsen]

I'm not sure about the resistor values for the front heater, since there are more than two speeds. But last year I replaced the resistor on the rear heater in my 24 volt HJ60. That rear heater blower only has two speeds, low speed (with a resistor), and high speed (bypasses resistor). I used a 20 ohm, 25 watt fireproof resistor based on what little info I could find, and it's been working fine. Ideally, I'd swap it out for a PWM controller to save some power but haven't got around to that yet.

 

[bj40green]

Here is a data sheet for (ceramic tube) wirewound power resistors.
Compare the dimensions your resistor with the ones in the data sheet to get an idea of the wattage.
Dimensions are in mm.
http://www.resistor.tw/spec-en-dr.htm

Good luck,

Rudi

 

[FF LC FREAK]

Thanks guys for the help!

First off, if I do the fuse amp x volts (20 amp fuse according to the owners manual x 24 volts) I get 480 watts. I don't know if they differentiate between 12 and 24 volts, though. But, that seems really high. On a 12 volt system, it is a 50 watt resistor (12x20=240). I guess if I divide by 5, I would get the proper 50 watt resistor. On a 24 volt rig, I would get roughly a 100 watt resistor using the same math.

But, using Rudi's link, I end up with measurements close to a 30 watt resistor. That would make more sense to me since a 24 volt system uses half the amps of a 12 volt system.

However, I did a little more research. My current resistor is roughly 3.5 inches (19 mm) long. Looking at the Allied Electrical website here - http://www.alliedelec.com/images/products/datasheets/bm/OHMITE/70022136.pdf - their 50 watt resistor is the closest match. That also coincides with a 12 volt resistor. Would Toyota have used the same resistor for both a 12 and 24 volt system?

So, now I'm a little confused. I might just order a 25 watt resistor (as close to 30 watts as I can get) and a 50 watt resistor. Try each of them and see which one works and doesn't overheat. Unless someone else has another idea, that will be my course of action. Does anyone have any better ideas?

Thanks!

 

[bj40green]

Here is a bit about how it works.
Let's say that the ventilator is 100W.
To reduce the speed there is a resistor in series which eat's up half the power. So 50Watts for the ventilator and 50 Watts goes into the resistor. The above is not 100% true but for explaining it's good enough.
So my advice is; buy the 50 Watt resistor and you're good.
Or wait till somebody else chimes in with the real specs.

Rudi

 

[Dbradford04]

Dude...I think I have one at home...I have a complete blower motor, and I think the resistor is there...I'll check when I get home later this month...let me know if you still need it.

D

 

[FF LC FREAK]

Thanks Dan! I might take you up on that. I don't mind getting a new resistor, though. They're only like $8 or $10. I just wasn't sure what to get. But, as you saw, I'm not going to need the heater anytime real soon. It was actually me pulling off the head that busted the resistor. As I reached into the engine compartment, I caught one of the connections with my sleeve and busted it off. As I tried to remove the resistor to fix it, it fell apart. Oh well.

 

[FF LC FREAK]

For a follow up, I bought an Ohmite 4 ohm 50 watt resistor (p/n L50J4R0E) from Allied Electronics. I put it on tonight and it works like a charm. The motor runs approximately 1/2 speed with this resistor, which seems about what the stock resistor did. It is a little longer and thinner than the original. I had to make a simple little bracket to make it fit in the stock area. Pretty easy.

 

[bj40green]

Good job! Another problem solved.
How warm/hot is the resistor when your heather is at 1/2 speed?
Can you touch it?

Rudi

 

[jmphilion]

I just bought this little guy on Amazon.ca for 4,48 $ !!

I will let you know how it goes once it gets here..

Green 50 Watt 4 Ohm 5% Aluminum Shell Wire Wound Resistor

de uxcell

 

[Diesel42]

Great thread, thanks for posting the research. Many, including me, will benfit from this sooner or later. Well done.

 

[jmphilion]

Ok, got it in..
It's smaller than i first thought.. If you ask why it's sideways.. Because it's got a little bracket on each side, i riveted it to the original resitor bracket in place.

Couldn't test it, there is something else wrong with my wires.

Pretty weird.. I'm getting no power at all at the blower unit plug, nor at the switch..
But the fuse is fine (same line as the filter light, that does light up at startup sequence).

I'll be spending some time with my old friend the repair manual.

J

 

[jmphilion]

Update!

It works fine! I get two speed like it used to.

That little heat sink is getting really hot reducing the speed. I let it run for about 5 min in the garage, so i guess it will get better ventillation on the road. Will check at intervals.

Btw, my other electrical problem was simply the ground that was not passing to the blower. So i added one from the blower to the body.

I had the same thing happening to my wiper motor, did the same.

 

[tornio]

hi guys , this is my first post ... so after have received a lot of help from all the forum (THANK'S) I want to help solve this little problem :

IF the blower is 100w let me say :

to reduce to +/- half speed we need half voltage so a 24v 100w motor need +/- 4,2 A

to drop half voltage ( r=v/a ) we need r = 2.85

the power dissipation of this resistor must be (w=va) 4,2 x 12 = 50.4 w

but somebody can say : why Toyota put 4 ohm instead of 3 ? I don't know why but :

normally the blower is on when also the engine is on .... so the voltage now is almost 28v

load 100w 28v is 3,5 amper

TO REDUCE TO HALF : 14V / 3,5A = 4 ohm

the power required is 14 x 3.5 = 49 w so 50w resistor is the same

how you say " this is only my little cent' "

Thank's to all guys !!!! an sorry for my english , (i want improve it)

this is my rusty rusty rusty 1983 bj42 180k km stock

 

[tornio]

I forgot to resize the photo .....

 

[ivanhoe]

You call that rusty, you haven't seen a Canadian BJ42. I like your roof camper

 

[jmphilion]

Sure is a nice roof tent! - thanks for the info as well, it helps understand how it works.
JM