PDA

View Full Version : heater/ac fan resistor module


fishermunn
06-28-2016, 12:44 PM
anyone help me locate the resistor module for the fan blower on my 2008 ncv3? the fan only works on the lowest speed. i have pulled the fan motor several times to grease the bearing to stop the squeaking noise.
appreciate any insight or helpful experience.

autostaretx
06-28-2016, 06:47 PM
In the T1N it was mounted in the engine compartment fairly close to the cabin air filter/fan box.

--dick

fishermunn
06-28-2016, 10:21 PM
Thanks, dick.
According to the fiche, it is supposed to be next to the blower unit.
I will take the glove box out and see if I can find it. I have taken the blower out several times, but never noticed the resistor module.
I "assumed" it was behind the switch on the dash board, but according to the parts guy at freightliner, it's next to the blower.

Aqua Puttana
06-28-2016, 10:50 PM
Assuming the design is similar, you should find that it inserts into the main duct. The air flow from the blower is used to help cool the T1N resistor pack.

vic

autostaretx
06-29-2016, 03:04 AM
Assuming the design is similar, you should find that it inserts into the main duct. The air flow from the blower is used to help cool the T1N resistor pack.

Yes, it gets rather hot.
(i'd eyeball it as at least capable of 25 watts, probably running at 10 watts)

--dick

Cvollmar
06-29-2016, 11:06 PM
It is to the left of the blower motor has a 4 pin wire connector. Turn it counter clockwise about 1/4 turn and it should easily come out. Installation is the opposite

fishermunn
06-30-2016, 01:18 AM
as stated by vic, the design is the same as the t1n and the resistor was in fact in the duct upstream of the blower. thanks for the direction, it was obvious once i looked for it.

it is mounted in the portal just like the blower unit, you twist it counter clockwise and it pops out with only the plastic power plug to remove.

i found one at napa and it looks identical and saves me around $20.00 on the part and the cost of shipping one from the nearest dealer.

my fan only works on the lowest setting. i turned it on with the resistor in hand and it does indeed get warm very fast. i can see how the cool ac air would help with heat. i wonder how it handles the winter heating needs? the heat sink on the resistor would be very hot with the heater turned up.

question for dick, when i powered the fan with a 12v battery on the bench, the #12 wire became very hot quickly. my electrical background is sketchy, the battery has a rating of 550 cca. was i sending too much amperage to the fan and heating the wires?

i included two pictures, one of the resistor, very cool looking and one of the open portal where if twists in to the housing.
.
thanks to vic, dic and cvolimar for the help.

autostaretx
06-30-2016, 05:28 AM
question for dick, when i powered the fan with a 12v battery on the bench, the #12 wire became very hot quickly. my electrical background is sketchy, the battery has a rating of 550 cca. was i sending too much amperage to the fan and heating the wires?

Batteries don't "send" current.. the load (fan motor) DEMANDS current.
The battery merely tries to supply what it can, and will be limited in doing so by its own internal resistance. If the battery is the limiting factor, you'll see the voltage at its terminals drop.

If a 12 gauge wire is getting very hot, your motor is demanding a lot of current.
Perhaps it has a shorted winding, and is the cause of damaging the resistor.
Put a fuse (matching the heater fan's rating in the Sprinter) in-line with your #12 wire and see if it pops. (or use a suitable ammeter... i use the $60 Craftsman clamp-on DC ammeter)

--dick
p.s. i'm jealous... the T1N just has a ratty flat ceramic package as the resistor.

77650

parmus
06-30-2016, 09:20 AM
I have just done the fan heater exersize. My fan was running slow as well but seemed to work off 12 volt for a short time. Replaced the resister unit that cost 200 dollars Australian and didnt help. Serious looking unit that i think will last forever. Borowed a mates spare fan motor and all works like a dream. I suspect it was a brush problem (the brushes work very strangly and are quite different from any i have seen before). The brushes seemed to be touching the com but may have been stuffed. My 2009 sprinter has done over 400k and the fan is on 90 percent of the time so i cant complain.

Aqua Puttana
06-30-2016, 12:55 PM
...

question for dick, when i powered the fan with a 12v battery on the bench, the #12 wire became very hot quickly. my electrical background is sketchy, the battery has a rating of 550 cca. was i sending too much amperage to the fan and heating the wires?

...
I'm not Dick.

The fan is a centrifugal design. With no back pressure created from being properly installed into the ducting system the spinning fan would hog air and overload. That is likely why you saw higher than normal current on a bench test. I wouldn't condemn the fan without further testing.

vic

fishermunn
06-30-2016, 04:31 PM
i hooked up the fan with a 30 amp fuse in line from battery and it popped within a few seconds.

vic, how would i test the fan to see if your idea is correct?

i now have a new resistor and fan on order, each returnable if i can find no fault with the original equipment.:popcorn::popcorn:

autostaretx
06-30-2016, 06:32 PM
i hooked up the fan with a 30 amp fuse in line from battery and it popped within a few seconds.

vic, how would i test the fan to see if your idea is correct?
I'm not Vic... but the simple answer is to block airflow through the fan.
So place a sheet of cardboard over the air-inlet (the big hole in the center), and then power it up.
(given your "30 amp fuse" test, i think your motor definitely has problems...)

Have you ever put your hand over a vacuum cleaner's nozzle and heard the motor speed up?
Same principle: if it doesn't get airflow, the fan blades don't have to work so hard to move it.
(they're spinning in a (relative) vacuum, so there's not as much mass of air for the blades to plow through)

I'm not so sure what blocking the outlet does (in terms of relative percentage of motor load).
Blocking the inlet lowers the load the most. Allowing free flow is (let's say) halfway-there.
Blocking the outflow allows the fan to still draw in new air, while at the same time it's busy trying to compress the blocked outflow.

Time to go put my hand on the ShopVac's outlet.... (watch this space) :professor:

Result: (ears ringing...) blocking the outflow makes very little difference in perceived (see "ringing") speed.
Blocking inflow definitely does.
(this may not be a perfect apple-to-apple test: the ShopVac may not be a centrifugal fan)

The "limiting" test would be to block rotation of the fan (screwdriver in blades). Don't try this!
But i'm pretty sure that would pop the fuse, too (and/or fry that section of the rotor). Don't try this!
(a DC motor's maximum power is consumed when the rotor is stalled (i think... running off to verify that)).
Yes... current is highest when the motor is stalled (by a LARGE factor).
ref: http://www.micromo.com/technical-library/dc-motor-tutorials/motor-calculations
note how the "current" (blue line) rises as the speed drops to zero (right end of curves)

--dick (sig moved when p.s.es expanded exploded)

synergy_58
07-10-2016, 05:24 PM
i hooked up the fan with a 30 amp fuse in line from battery and it popped within a few seconds.

vic, how would i test the fan to see if your idea is correct?

i now have a new resistor and fan on order, each returnable if i can find no fault with the original equipment.:popcorn::popcorn:

Get anywhere with your fan motor yet? I'm in the same boat. I now have my fan motor and resistor out, ready to move forward but not sure whats wrong, exactly. The fan works when I juice it up with 12volts. The resistor, I'm not sure how to fix.

Where did you buy yours from? Is it working?

fishermunn
07-10-2016, 11:46 PM
sorry, i got busy and forgot to finish how all this turned out.

i bought the fan motor and resistor from napa. it saved me shipping and was available the next business day for pick up.
since the original fan motor blew the 30 amp fuse when bench tested, i tried hooking the new motor up with my original resistor in place. all 4 fan speeds worked, so i returned the resistor, unopened, and they graciously took it back without a restocking fee.

thank you dick! i was assuming it was the resistor and would have plugged it in first if you wouldn't have chimed in. you saved me from buying a $100.00 part that would not be returnable if opened.

the fan motor and resistor are easily removable and certainly a job that be done by anyone willing to try it.
read this link: http://sprinter-source.com/forum/showthread.php?t=26035&highlight=fan+motor

AtlasAxle
09-14-2016, 07:48 AM
All my heater & resistor problems on my 416 started and finished with corroded connections, check & clean all associated connections before replacing anything. 😊 Regards Atlas