2 speed electric fan: broken, or am I doing something wrong?

[BerniniCaCO3]

Getting ready to drop in my electric fan.
I had it and a spare battery, well, a large jump box, on the bench and wanted to know which was high speed and which was low.

I figure that it'll draw however much current it needs, that's how electricity works ya know. Fuses aren't necessary unless something's shorting.

Well, I hooked the green wire to the negative clamp, and touched the red positive clamp to one of the two black leads. Fan turns on. Seems like it moves a lot of air, maybe this is the high speed?

Move it over to the other black. Uhhh... the fan does not move, and smoke starts coming out of the back, particularly right past the harness.

Is there an internal short in the motor, time to go back to the junkyard?
Or was there supposed to be a fuse or anything else?? I'm thinking the former though, just want to make sure it wasn't anything wrong with hooking the fan directly to a battery that did anything.

Taurus fans are also 2 speed and just as good as the mark viii ones?

[BerniniCaCO3]

I don't know enough about motors: internal short must be the cause, not brushes or bearings etc.?
I'm thinking spending $70 on a replacement motor might not be a bad idea: I'd probably still have a better fan with now a new OE motor, than spending $100 on a china fan.

[1987cp]

If you get a Taurus fan, make sure it's from a 3.8L car. I ended up with the smaller one from a 3.0L car since at the time I couldn't get a single person to cough up any info other than "Uh, 95 Taurus, man." The one I have is adequate, and the compactness is nice, but I'd be a little happier if it were the bigger 3.8L fan.


BTW, what's this about spending $100 on a fan? New Sentra fans are like $80, and they're supposed to be excellent.

Whether it's worth getting a new motor for your fan is up to you. I know a place here that sells used fans for as cheap as $25, but I'll be the first to admit that mine is slightly noisy.

[tjc78]

If you get a Taurus fan, make sure it's from a 3.8L car. I ended up with the smaller one from a 3.0L car since at the time I couldn't get a single person to cough up any info other than "Uh, 95 Taurus, man." The one I have is adequate, and the compactness is nice, but I'd be a little happier if it were the bigger 3.8L fan.

Could you grab one from those late 80s early 90s FWD Continentals? They were Taurus based and only came in 3.8 IIRC.

[1990LTD]

Could you grab one from those late 80s early 90s FWD Continentals? They were Taurus based and only came in 3.8 IIRC.

The updated version of the Taurus based Continental had a 4.6 as well, perhaps the fan would be equal or greater than the 3.8? Don't know about fitment since people have only discussed the 3.8 fitting. The modular Continentals were 95-2002

[gadget73]

are you sure that green is negative? I seem to recall my Mark 8 fan having a black negative, and an orange and yellow for the+ feeds depending on the speed. Black is generally DC negative, green is ground with house wiring.

[GM_Guy]

What is the fan out of?
Some fans 2nd speed works by applying voltage to BOTH terminals. Some by one or the other. Some do ground switching just to add to the confusion. =-)

Alex.

[BerniniCaCO3]

mark viii
should I try voltage to both terminals?

[BerniniCaCO3]

let me know what the case is for a mark viii fan specifically.
I'd swear it's green w/ black line, black, black-- but maybe one of those is just sooty and had a stripe or something

To further add confusion, there were 1 and 2 speed fans. I presume that 3 leads == 2 speed?

[Lincolnmania]

you will burn the fan up running power to both wires at the same time

[1987cp]

Do I need to go searching for my fan-plug picture again? On mine ('95 Tortoise 3.0L), one of the two outer leads is ground; put a big wire there. Middle lead is hot for low, opposite lead is hot for high, have to disconnect low to engage high (SPDT relay time).

[BerniniCaCO3]

right: I don't intend to run hot to both at the same time!
But I need to know which is the ground and which 2 are the hot! I'd naturally concluded that 2 black & 1 green meant hte green was ground, but when one of the blacks + green = smoke and an obvious short, that natural conclusion must not be right!

I don't have the plug, but 1987cp, if you can trace whether the green wire is a ground or a hot do let me know.

[BerniniCaCO3]

Hah! whoops!
On the suggestion that it must be a black wire that is a ground, I double checked...
"-BLACK Outboard black lead is a GROUND.

+BLACK Center lead is a POSITIVE lead...actuates fan on engine temp.

+BLUE Outboard lead is a POSITIVE lead..actuates fan w/ aircon."

Hahahahahaha. SO, when I connected blue, thinking it was ground, to the black that was actually ground, it ran at low speed. When I connected blue to the OTHER black, which was ...also hot... It was just running in an wonderful O-resistance circuit, making lovely smoke.
Seems to still run. Whew.

I'm guessing blue (A/C) is probably low speed, but honestly I can barely hear the difference between the 2 speeds... mind looking up for me?

I'm following a fellow's plans for a 4-relay, 2 temperature-sensor design that uses the relays to switch off the low circuit when it turns on the high. Ought to work, once I figure which is low and which is high!
I'm heating up a pyrex of oil with a candy thermometer to test the whole setup outside the car. Last thing I want to do is be on the beltway breaking in the new engine and discover that the radiator fan doesn't work.

[BerniniCaCO3]

huh, yeah, my father can't tell the speed difference either

[1987cp]

Why would you possibly need four relays? Probably better post up the circuitry this person suggested so we can pick at it.


You must have completely missed my comment on employing a SPDT.


SPDT relays have a central post that is normally closed; powering the relay cuts that off and engages the normally open terminal. That's how I make the switch from low speed to high speed. A normal 40-amp SPST relay switches the fan on and off. Two relays, that's it.



That said, since my setup uses a temp probe to engage low speed and the A/C signal to switch to high speed, I am interested in adding either a third relay or possibly a transistor so that low can be engaged with either A/C or the temp probe, with high speed coming on only if both signals are present. Since the third component would only be switching a low-current signal, I'm pretty sure a transistor should be adequate for the job, leaving more relay spots on my fusebox open for other uses.