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a_2000_se

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Discussion starter · #1 ·
...did a quick search and didn't see a specific value......

I just measured the cooling fan resistance at the connectors, (fans isolated, connectors removed). This is on an 11/99 car, SOHC, SPI, VIN P

Both fan coils measured approximately 0.5 ohms.
(half an ohm, reversed the leads to check for diode and got half an ohm both ways.)

I have a spare fan motor from 2001 or 2002 SOHC car in my box of spare parts and it measures 13.5 ohms. It is for all practical purposes a 'NEW' fan motor (the car had only 400 miles on it).

For grins the Cooling Fan Resistor measures out at approximately 0.5 ohms also

The question: Did the cooling fans change part numbers for later cars or are my fans indicating a potential future problem at 0.5 ohms? (They are working fine with no related fuse, relay or wiring problems.)
 
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Discussion starter · #3 ·
Yeah - I'm not liking what I'm seeing either.

Actually, on my year at least, the fan motors are paralleled and in series with the fan resistor so total resistance is .5+ 1/2(.5) or .75 ohms. Total circuit current is ~18amps or ~9amps through each fan - Low Speed, Assuming 13.5volts. This branch is Fused at 30amps.

High Speed - This gets ugly. It's fused at 50amps and could be very close to that since there is no fan resistor.

I measured a fan assembly on a same year salvaged car. One fan motor was .5 ohms and the other was 2.5 ohms, connectors open fans isolated.

Could this be a sign that the insulating coating on the fan motor windings is breaking down, eventually leading to a cooling fan failure and damage to more than just a fuse, relay, harness or worse......

That's a big change in resistance from 10 - 13 ohms new to 0.5 ohms 11 years later. I think I'll look into having the electric motors rewound/rebuilt.

Anyone else want to measure their cooling fan motors coil resistance? Disconnect the connectors first.
 
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Discussion starter · #4 ·
Got some more info and did some digging around.

Trivia:

Ford wants $450 for a new cooling fan assembly on my year car.
Tousley would do it for $272.50 plus shipping.

Ford doesn't sell just the electric motors themselves.


From the 'NEW' spare parts motor I have:

BOSCH T Made in Mexico
GPB 684 12V F 00H X2B 004 00
904 CW 28319 2 NOM

The important info here is :
Type GPB, 12 volt motor.

I found on Bosch's site something very close, in looks and specs but don't see what the connector looks like: Part number 3 137 227 744
Not the exact part number nor is the exact part number on their 'Part Number Listing' page.

Image


http://www.boschmotorsandcontrols.co.uk/elektromotoren/produkt/3137227744/index.htm

If we take the following specs:

Nominal voltage UN 12 V
Nominal power PN 181 W
Nominal current IN 20 A

And if we use the Nominal voltage and current we get:

coil resistance of 0.6 ohms.

which is probably within the error of the meter I used when I got 0.5 ohms.

I guess things are where they should be with my existing fan motors......
All seems to be good.
 
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#6 ·
Buy just a resistor?

mikeeshaq said:
with 13.5 ohms = ~ 1 Amp
With .5 ohms = ~25 Amp
[I=E/R] I=current in Amps, E=Volts, R= ohms

Watts = I squared R
1x1x13.5=~13.5 Watts
25 x 25 x .5= ~325 Watts
Click to expand...
This thread, http://www.focusfanatics.com/forum/showthread.php?t=114907&page=15, and http://www.focusfanatics.com/forum/showthread.php?t=322169&page=4 are awesome for what I've been dealing with (and every other Focus owner it seems).

However, instead of buying the $45 plug/wires/resistor from the parts store, I was wondering if I could just buy the resistor at Radio Shack, snip off the old one in the holed cage thing, and solder the new one on? Which size resistor would I buy? I cannot find this answer anywhere. Yes, the resistor is fried, I tested it with a multimeter. Radio Shack sells resistors by watts, and I know I haven't forgotten that much physics, but isn't the rating in ohms?

From http://www.focusfanatics.com/forum/showthread.php?t=322169&page=3
FocusKnot said:
I measured 4.55 volts across the resistor with the fans running. The resistor measured about 1 ohm. That means about 21 watts of heat is being generated.
Click to expand...
So am I buying a ~21 W resistor?

Thank you in advance!
 
#7 ·
You found some good threads for reading, what I wonder in response to your question is whether Radio Shack sells resistors in that high of a power rating (open coil style).

My old resistor color code chart is hidden away elsewhere, so I can't refer to it easily. IIIRC the ohm rating on all the small ones is followed by the Watt rating so both measures are needed to size one correctly, even in the smaller sizes.

So you're absolutely correct, Ohms plus watt rating to get the right fitment.

If you had some Nichrome wire handy, in an appropriate diameter, you could measure the right length & coil it on a rod to make your own high power resistor (grin).

Luck
 
#8 ·
LightningFocus said:
So am I buying a ~21 W resistor?
Click to expand...
No! Resistors must have a power rating that is greater than the heat they are dissipating...the more the better.

Also, my resistance measurements are not that accurate. Measuring very low resistances is tricky and requires very good equipment. My measurements were made with a cheap VOM and intended to only convey the thought that the fan resistor gets very hot and eventually destroys the OEM connector.

The fan resistor is designed to dissipate its heat into free air. If you were to replace it with a high power (let's say 50W) resistor, most of those are designed to be mounted to a heat-conducting surface. The fan shroud would not be suitable for that.

Without going into a lot more, my short answer is, do not attempt to replace the fan resistor with anything other than what it came with.
 
#9 ·
sailor said:
If you had some Nichrome wire handy, in an appropriate diameter, you could measure the right length & coil it on a rod to make your own high power resistor (grin).
Click to expand...
If... Ha. Some day I'll have everything in my garage.

FocusKnot said:
Without going into a lot more, my short answer is, do not attempt to replace the fan resistor with anything other than what it came with.
Click to expand...
Well damn. I guess I'll just spend the money and (from what it seems) replace it every 2/3 years.

Time to get at this before the rain comes for the day.

Thank you all very much!
 
#10 ·
If you get the new design, it comes with pigtail leads and the connector is not used. In theory this should make the fan resistor much more reliable. I have not heard of any of these failing, so maybe that is a good sign.

In the rust belt areas, the fan resistor is subject to extreme corrosion that can kill it. The corrosion causes localized heating where the wire gets pitted and this often causes the wire to burn completely through. You will see many of those with gaps in the wire where this happens. I noticed that you live in Florida, so that should not be an issue.
 
#11 ·
FocusKnot said:
If you get the new design, it comes with pigtail leads and the connector is not used.
Click to expand...
The one I bought looks just like the old one. No special designs. Lifetime warranty - which is nice.

Would you suggest doing what you did in this post:

FocusKnot said:
Photo 5 shows how I made a repair by drilling a hole in the male terminals and attaching ring terminal connectors as I described in my earlier posting
Click to expand...
Does this help dissipate the heat and not cause another blowout?
 
#12 ·
I would recommend what I did to fix my resistor to those that are able to do it. My car has the original fan resistor which I had to repair as described in that thread. We don't have severe corrosion issues here in Dallas, so my resistor was in good shape. What failed was the connector, and with that eliminated, I expect a very long life from it...perhaps the life of the car. That's also why in the new design they eliminated the connector altogether.

BTW, some have repaired their resistor by drilling holes in the terminals and soldering pigtail wires (or the harness directly) to them. That should work equally well.
 
#13 ·
LightningFocus said:
If... Ha. Some day I'll have everything in my garage.

Thank you all very much!
Click to expand...
Hope you enjoyed the tongue in cheek comment on how to make your own resistor.

That kind of do it yourself came from old Radio/Electric literature and would be more useful in making a custom heating element.

As long as a replacement is avail. it's better than going to that extreme for most.

Cheers
 
#14 ·
The actual resistor pretty much does not fail, i.e. the looped coil there, it can be used over and what I did and working fine now over a year later. The part that pops is the thermal limiter right before it, the small diode looking thing, it melts when it hits a certain load like a fuse. Commonly though the connector can melt first.

In reference to the OP, I'm wondering if full length carbon brushes add a bit more resistance to brand new motor numbers, ergo, why the heavily used ones read lower, brushes are very worn to lower that. The carbon often is a resistance.........someone feel free to correct me there.
 
Discussion starter · #15 ·
Three years later and probably 35k miles (180k+ total), still on the original fans.

Sooooo.... This now means they will fail tomorrow? Lol.

For the last 3 or 4 years I've had my scan gauge set to warn me when the temperature exceeds 223 degrees F. The low speed fans turn on around this temp here or maybe slightly lower, so I get an audible warning one time. I glance at the gauge display and the temperature is already dropping (a lag time between reporting alarm) so I know my low speed fan is still functioning.

Maybe I should start looking for the replacement fans. Yes. Resistance of the brushes could very well change as they wear.

Here is the question though....... What is the highest mileage anyone has got on their original fans and how much have you used your AC (since your fans are always on when the AC is on and at HIGH speed too)?
 
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#16 ·
I have LEDs that tell me low and high fans are on, as well as a/c clutch cycling.

I'm bumping 200K with one car and the fans were torn up in accident, I rebuilt the shroud and same exact fans used over. Still working now.

In my view the fan motors on these are quite awesome, I still have original fan motors in 2 Tempos and a Contour as well, they just don't die. I'm pretty sure aftermarket can't touch that.

Here in Texas, you gotta have working a/c or the car does not get driven............
 
Discussion starter · #17 ·
That's good to know, a few more years on these fans. We haven't used the AC much over the years, so that may be good for an extra couple years too. Hmmmm what will fail first on this nearly original car......
 
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#18 ·
I bought a new cooling fan resistor unit. Both it and the old one measure .3 ohms at the terminals, and .1 ohms on either side of the resistor itself. No fan comes on until 230-233 degrees F. Could the new resistor unit be bad?
 
#19 · (Edited)
cstarkeyc said:
I bought a new cooling fan resistor unit. Both it and the old one measure .3 ohms at the terminals, and .1 ohms on either side of the resistor itself. No fan comes on until 230-233 degrees F. Could the new resistor unit be bad?
Click to expand...
The resistor does not determine when the fans run - the PCM does based on input it receives from various sensors/switches. Resistor only determines low speed fan speed. And your resistor specs out OK.

Do your fans run with the AC on (engine cold or hot)?

Paul
 
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#20 ·
cstarkeyc said:
I bought a new cooling fan resistor unit. Both it and the old one measure .3 ohms at the terminals, and .1 ohms on either side of the resistor itself. No fan comes on until 230-233 degrees F. Could the new resistor unit be bad?
Click to expand...
Those resistor measurements are about right. The actual resistance is so low that most cheap meters cannot accurately measure it.


Are you trying to tell us that you don't have low speed operation...just high speed?


If that is the case, then you may have a bad relay.
 
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