This is what the OE unit looks like:
That very fine coil in the front is for the low speed blower in series with those three much larger ones. Has twice the resistance as the combined other three, with 7 amps of low speed current, they expected that 11 mil wire diameter to safely handle 60 watts. No wonder why mine was powder.
Course Toyota wants around 70 bucks for a new one, but getting the same piece of crap that will also burn up.
So I rolled my own using 35 mil wire but instead of six inches, had more like 18" to jam in that small spot, so this is what I ended up with.
This should last a lot longer. Least I have low speed again.
Edited: Wed May 09, 2012 at 7:38 PM by NickD
Nick you're a wild man... now that is sweet! And you saved the price of roughly a tank of gas. Question is, does the blower operate at roughly the same speed?
I also remember when you repaired the blower motor control on the Caddy... built it better than before. You could probably sell that service on the Caddy forums.
I'm just curious about the wire used... is it a different material that provides less resistance? Can't be just copper right? A special kind of "resistor" wire. Forgive my electrical ignorance...
What's the resistance across each section?
(My toyota truck has only 2 speeds now (out of 4), so I'll probably do something similiar.....)
Its called nichrome wire, same stuff used in an electric space heater, range, or your electric dryer. It can run red hot for years.
At first, I duplicated the original design just to replace it like it was, that was easy, but running it at 6.5 amperes, it practically lite up my work area like an incandescent bulb. Granted, it is located downstream from the blower motor circuit for additional cooling, I was operating at free air, but wasn't too happy with that.
Toyota manual was nice enough to state the resistance of this leg is 1.25 ohms. I just use my micro ohmmeter clip a lead to one end of a piece of wire and run the other end until my meter read 1.25 ohms.
First try was a failure, wound it on a 1/2" mandrel like the coil on the original at the rear, was too close to the plastic in the blower housing. So went down to a 1/4" mandrel and mounted it as shown. The base is actually of good quality, bakelite, can hold an 800*F soldering iron tip to it and not even dent it. Also the ends are soldered to brass terminals, require a special flux for that.
In running 6.5 amps through the larger coil, didn't even turn red, was happy with that. Yes, the blower in low runs at the same speed. Other coils checked out, but their total resistance was around 0.65 ohms, so there super tiny coil was dissipating over twice the power as the other three.
Was easy to remove it in the Supra, three screws for the lower dash panel, remove the connector, one screw for the blower resistor. But had to bend like a pretzel to get it out. Straightening out my old body wasn't easy. LOL.
These are made kind of cheap, many use a brass rivet that turns green for additional problems, and does look like a breadboard to me. Used nichrome a lot in the past, but always on a ceramic core for better heat dissipation. Same stuff is also used in a fuel sender, repaired those as well. If you take your time, can actually make an accurate gas gauge.
Most likely completely irrelevant, but on my 1988 Mazda B2200 truck here are the blower resistance measurements in ohms:
L about 2.0 low
M about 0.9
H2 about 0.3
H1 continuity (0 to 0.1) highest speed
And mine looks very similar to the one in the photo.
Toyota manual just gives the resistance of each of the four resistors, so some serious math would have be used to calculate the total resistance for each speed range. Like adding, LOL.
But two ohms is just about right on for the low speed.
Practically all the electrical on this thing is from Denso, assume your Mazda is the same.
You mentioned that you soldered the nichrome wire. Do you think that will last? Ithought that nichrome wire terminals were spot welded. I did not think solder would hold very long.
Thanks for the refresher... now I remember. I think it's awesome too that you matched the exact resistance, with a little thanks to good Toyota documentation!
Originals were soldered with good old fashion 60/40 rosin core lead tin. In that brass spade, a small "V" was stamped, cleaned that out with a desoldering tool and a bit of help with a .035 drill so the new wire would stick in that hole and can be crimped. Than the solder goes up along the nichrome to lower its resistance. Brass terminals barely get warm.
Seen others where just a brass rivet is used that burns and gets all corroded, clean those up with a wire brush and solder them, then they last forever.
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