The resistor in my 2003 Sprinter 2500 keep going bad after a few hours. I have replaced 4 in the last month. Does it have something to do with the blower motor ?? The van is modified to carry my wife who is a quadriplegia with MS so I really need the heater/ac in working order. Can anyone help me solve this puzzle ?
Blower motor resistor problems
- Thread starter Rangeley
- Start date
First let me extend you a hale and hearty welcome to the forum. 
That is too many failures for things to be normal.
My first guess would be some sort of harness/wire problem. Some people have had problems with critters getting into the engine bay and chewing wires. Poor connections or grounds may cause local heating. Do the resistor connections proper show signs of heating or melted insulation? A problem there would transfer more heat to the already hot resistor assembly.
Another possibility might be that the blower motor bearings are going bad which might put additional load on the blower supply. The blower fan is available to the left of the engine bay. You should be able to reach in and spin it with your hand to see if it seems tight or moving freely.
There is a cabin air supply filter under the hood near the center. That could be plugged and restricting air flow which is used to help cool the resistor assembly while in use.
Good luck.
vic
That is too many failures for things to be normal.
My first guess would be some sort of harness/wire problem. Some people have had problems with critters getting into the engine bay and chewing wires. Poor connections or grounds may cause local heating. Do the resistor connections proper show signs of heating or melted insulation? A problem there would transfer more heat to the already hot resistor assembly.
Another possibility might be that the blower motor bearings are going bad which might put additional load on the blower supply. The blower fan is available to the left of the engine bay. You should be able to reach in and spin it with your hand to see if it seems tight or moving freely.
There is a cabin air supply filter under the hood near the center. That could be plugged and restricting air flow which is used to help cool the resistor assembly while in use.
Good luck.
vic
hulagun
Haulin' A** since 1974
Rangely,
I just replaced my van's 2nd resistor in 2 years last week and took the opportunity to pull out the fan motor - because I read somewhere on this forum that it was a good idea to lube the bearings and such. Apparently a motor that is getting old or dry can cause resistors to shorten their life.
I was able to get the motor out of the housing, apart from the fan blades... with a lot of grimy cussing... but it is a sealed unit and there is NO way I could see to lube any bushings or bearings without further tricky disassembly. I squirted some TriFlo at the shaft and put it all back together. Not sure it made any difference. But it is working on all 4 speeds for the time being.
My recommendation is to replace your cabin filter, check that there are no other blockages in the vent system, and if no other problem is found... spring for a new OEM fan motor. IIRC, they cost about $150. But at the rate you are buying resistors, that may be a bargain.
I just replaced my van's 2nd resistor in 2 years last week and took the opportunity to pull out the fan motor - because I read somewhere on this forum that it was a good idea to lube the bearings and such. Apparently a motor that is getting old or dry can cause resistors to shorten their life.
I was able to get the motor out of the housing, apart from the fan blades... with a lot of grimy cussing... but it is a sealed unit and there is NO way I could see to lube any bushings or bearings without further tricky disassembly. I squirted some TriFlo at the shaft and put it all back together. Not sure it made any difference. But it is working on all 4 speeds for the time being.
My recommendation is to replace your cabin filter, check that there are no other blockages in the vent system, and if no other problem is found... spring for a new OEM fan motor. IIRC, they cost about $150. But at the rate you are buying resistors, that may be a bargain.
autostaretx
Erratic Member
Here's a screen grab of an old thread.
Note the cylinder on the left side of the resistor.
That's a "thermal fuse" .. and when it pops, the motor stops.
You could replace it with a (not too much) higher-rated fuse, or at least with the 420F part listed in the text:
good luck
--dick
Note the cylinder on the left side of the resistor.
That's a "thermal fuse" .. and when it pops, the motor stops.
You could replace it with a (not too much) higher-rated fuse, or at least with the 420F part listed in the text:
good luck
--dick
MercedesGenIn
Mercedes-Benz Resource
Hi there,
It would be a good idea to have a close look-see at the plug in connector and its spades. Often due to the placement of this device weather/moisture etc gets to work on the contact spades. Corrosion causes some low resistance to the joints and secondary heating occurs (Quite large current is drawn by the blower motor - check out the cable size!)
One or two things could be happening here:
The extra heat produced from the tarnished corroded spades in the connector is adding to the heat produced in the 'dropper' itself thus terminating it more quickly due to overheat - or the other units are not faulty (assuming they are not obviously visibly blown apart!) and you could have a reoccurring poor connection in the connector.
Additionally - I would not totally discount an intermittent motor with a dead-spot on the commutator/poor brushes, especially if the other speed control resistors were found not to be faulty.
All the best
Steve
It would be a good idea to have a close look-see at the plug in connector and its spades. Often due to the placement of this device weather/moisture etc gets to work on the contact spades. Corrosion causes some low resistance to the joints and secondary heating occurs (Quite large current is drawn by the blower motor - check out the cable size!)
One or two things could be happening here:
The extra heat produced from the tarnished corroded spades in the connector is adding to the heat produced in the 'dropper' itself thus terminating it more quickly due to overheat - or the other units are not faulty (assuming they are not obviously visibly blown apart!) and you could have a reoccurring poor connection in the connector.
Additionally - I would not totally discount an intermittent motor with a dead-spot on the commutator/poor brushes, especially if the other speed control resistors were found not to be faulty.
All the best
Steve
sarl_cagan
2006 118" SHC in Portland, OR
Reviving another blower resistor thread!
Finally got around to testing out the fan/AC/Espar situation on the van today. 5 months into ownership... I'm slow. I had the ole "blower only works on high" scenario but it did indeed blow. I went to swap in a new resistor (link here... thanks @gilee) and found the old was was particularly difficult to remove. I suspected maybe some plastic had moved around in there. Sure enough, I found that one of the wires (pin 4) on my van side connector has fried.
A few questions for you all:
1) I'm not really an electrical guy so when things are melted, I tend to proceed with added caution. Would this be considered a "normal" failure? Or cross into the realm of likely sketchy mouse chewed wires somewhere deep in the firewall? I'll try and scope out what I can in terms of nibbles tomorrow.
2) Is there a fuse I can pull to ensure this connector doesn't receive power until I figure out a solution? Sure... I won't have a blower, but that's ok for now. Maybe this one (see below)? Any reason not to do this? Am I overthinking this?
3) Any recommendations to remedy this? A few thoughts come to my mind:
A) Snipping a van-side connector out from a donor Sprinter, snipping out mine, and crimping connectors to both and connecting them. Finding a donor Sprinter is not super easy... especially for something this small.
B) Mayyyyybe I can de-pin that connector and find a replacement? I need to check if the metal that disintegrated is the connector or the pin.
(edit 1- I noticed there is a VW and Audi symbol on the connector. After some googling, I found THIS. Then it cross referenced to Dorman Part Number 645707 at Rock Auto... Anyone gone down this road before? They sure look similar)
(edit 2 - heck... even Amazon has them - HERE)
C) Plug in the new one and let 'er rip... maybe it will still work... blower was working when I unplugged it! (I'm afraid of an accidental short though)
On the plus side, my air condition AND Espar showed good signs of life! I had considered them both dead to the world. The bacon button didn't do anything at first and then right when I gave up... mini jet sounds. The Espar even greeted me with an spark-like ember out of it's exhaust. I'm not sure the last time it was used. I need to learn how to make sense of the AC data coming out of the AP200. Air seemed cold.. but it was also not warm out side.
Thanks everyone
Finally got around to testing out the fan/AC/Espar situation on the van today. 5 months into ownership... I'm slow. I had the ole "blower only works on high" scenario but it did indeed blow. I went to swap in a new resistor (link here... thanks @gilee) and found the old was was particularly difficult to remove. I suspected maybe some plastic had moved around in there. Sure enough, I found that one of the wires (pin 4) on my van side connector has fried.
A few questions for you all:
1) I'm not really an electrical guy so when things are melted, I tend to proceed with added caution. Would this be considered a "normal" failure? Or cross into the realm of likely sketchy mouse chewed wires somewhere deep in the firewall? I'll try and scope out what I can in terms of nibbles tomorrow.
2) Is there a fuse I can pull to ensure this connector doesn't receive power until I figure out a solution? Sure... I won't have a blower, but that's ok for now. Maybe this one (see below)? Any reason not to do this? Am I overthinking this?
3) Any recommendations to remedy this? A few thoughts come to my mind:
A) Snipping a van-side connector out from a donor Sprinter, snipping out mine, and crimping connectors to both and connecting them. Finding a donor Sprinter is not super easy... especially for something this small.
B) Mayyyyybe I can de-pin that connector and find a replacement? I need to check if the metal that disintegrated is the connector or the pin.
(edit 1- I noticed there is a VW and Audi symbol on the connector. After some googling, I found THIS. Then it cross referenced to Dorman Part Number 645707 at Rock Auto... Anyone gone down this road before? They sure look similar)
(edit 2 - heck... even Amazon has them - HERE)
C) Plug in the new one and let 'er rip... maybe it will still work... blower was working when I unplugged it! (I'm afraid of an accidental short though)
On the plus side, my air condition AND Espar showed good signs of life! I had considered them both dead to the world. The bacon button didn't do anything at first and then right when I gave up... mini jet sounds. The Espar even greeted me with an spark-like ember out of it's exhaust. I'm not sure the last time it was used. I need to learn how to make sense of the AC data coming out of the AP200. Air seemed cold.. but it was also not warm out side.
Thanks everyone
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B
billintomahawk
Guest
I'd drop the fan out and check for debris like dead mice, nests or only the Sprinter gods know what jam caused the burnout.
With the fan out you can check it for easy rotation, clean it, etc. Mine had 3 dead mice....
bill in tomahawk
With the fan out you can check it for easy rotation, clean it, etc. Mine had 3 dead mice....
bill in tomahawk
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gilee
2006 Sprinter 2500 Camper
I also replaced my resistor pack, bought it cheap on ebay from China. It works well on my previous sprinter. I didn't get melted socket, so lucky me.
With 200K miles, I also drop the motor to replace the carbon contacts... and lub/clean the fan a little.
I do see many debris and ppl talks about dead mice too, so this time I added a net around the vent to the hood. just in case.
I also insulated the Blower housing before wrapping back to original insulation on for stock looks.
Going by the pictures it doesn't look like it would fit, but my opinion should not stop you from trying it.
The damaged connector.
There's no real danger. The issue isn't really the melted insulation, but the condition of the molded in slide on connector. If the female slide connector has not lost it's ability to clamp the resistor male slide and the female slide can be cleaned up, it might be reusable. One repair could be to cut the melted connector loose, cut back the burned wire, and crimp on a short piece of wire with a new female slide connector. The chopped up OEM connector would then be installed with the new crimp connector installed after the OEM connector is in place. If you are concerned about electrical insulation a bit of Duct Seal or other putty could be used to cover the new crimp connector after installed.
vic
gilee
2006 Sprinter 2500 Camper
You right Aqua, I thought it was camera angle at first, but you are right. it is Much Bigger... as long as it gets through the hole, it has room inside.
For my new resistor, the Connector is slightly different too, especially the Notch that holds to resister in place, is not right, so I made some DIY mods and it fits perfectly. Incase you or anyone runs into this as well in the future.
As you see what I circled in red, the GAP is much smaller on the new resistor, so it won't slide in and lock. so I just cut some off, make that notch thinner, and it fits perfectly.
autostaretx
Erratic Member
Middle things first: YES, fuse 21 on the steering wheel panel will disable *only* the fan motor.
It can happen if the springy contact metal "relaxes" a bit, leading to (slightly) less than wonderful connection.
Running the fan at full tilt all the time maximizes the current, so heat can happen (this is why the resistor block has a thermal fuse hanging on it ... it also shuts down the cabin fan in the event of a fire (from any source).
I'm assuming that's "pin 4" that's melted (see left diagram below) ... it may have popped the attached thermal fuse (an ohmmeter across it would tell all)
You can certainly pull the fuse for peace-of-mind.
The heat can remove some of the "springy" properties of the socket's pin
It doesn't matter much if it melts through to the adjacent pin, since they're all just (eventually) going to the fan.
If the thermal fuse is melted, nothing is going through that pin at the present anyway.
I'd recommend wrapping the shell in tape, but the heat will both melt the adhesive and the tape.
As Vic wrote, you can continue to use the existing socket.
Your fan motor may well have worn bearings or diced mice inside it, causing it to require (demand?) more current to turn at all, leading to the melted pin. Opening it up and cleaning it would not hurt.
--dick
Page in service manual covering the resistor block:
A melted plastic connector shell like that is usually due to *slightly* higher resistance on the pin .... current through resistance causes heat.
It can happen if the springy contact metal "relaxes" a bit, leading to (slightly) less than wonderful connection.
Running the fan at full tilt all the time maximizes the current, so heat can happen (this is why the resistor block has a thermal fuse hanging on it ... it also shuts down the cabin fan in the event of a fire (from any source).
I'm assuming that's "pin 4" that's melted (see left diagram below) ... it may have popped the attached thermal fuse (an ohmmeter across it would tell all)
You're not over-thinking this, although there should only be current flowing through that pin when the fan is on.
You can certainly pull the fuse for peace-of-mind.
If nothing else, simply plugging/unplugging the resistor block a few times will "clean" the contact surfaces.
The heat can remove some of the "springy" properties of the socket's pin
It doesn't matter much if it melts through to the adjacent pin, since they're all just (eventually) going to the fan.
If the thermal fuse is melted, nothing is going through that pin at the present anyway.
I'd recommend wrapping the shell in tape, but the heat will both melt the adhesive and the tape.
As Vic wrote, you can continue to use the existing socket.
Your fan motor may well have worn bearings or diced mice inside it, causing it to require (demand?) more current to turn at all, leading to the melted pin. Opening it up and cleaning it would not hurt.
--dick
Page in service manual covering the resistor block:
autostaretx
Erratic Member
The Dorman socket looks like a reasonable substitution ... but if the blower motor is demanding extra current, the same problem may recur.
--dick
--dick
hulagun
Haulin' A** since 1974
When I did my trailer wiring I sealed up any exposed electrical crimp connectors using "Liquid Electrical Tape" available at Harbor Freight and other places. It works well. I am also a fan of self-sealing super tape on bundles of small wire or single 2-8 gauge wire (like battery cables) however it is awkward to wrap around a single 10-18 gauge wire. That's where the liquid tape worked nicely.
hulagun
Haulin' A** since 1974
Gilee, If you could create and post a tutorial on how to disassemble and lube or repair the Sprinter vent fan motor, I would be grateful. I could not see a way to crack open the fan motor in my 2005 Sprinter.
I would believe that mice can chew thru most "net" material. I imagine you used metal mesh of some kind? I would love to see your method here too, even just a photo.
Thanks!
marklg
Well-known member
My solution for rodent proofing is hardware cloth. It's a grid of fairly strong galvanized steel. They won't chew through it. I think it is too strong and it tastes bad. My problem was roof rats, so the 1/4" worked. They sell 1/8".
Regards,
Mark
B
billintomahawk
Guest
gilee
2006 Sprinter 2500 Camper
When I get home, will share more detail info.
I didnt open up the motor, not able to. So only changed the brushing and lube both ends from exterior...
sarl_cagan
2006 118" SHC in Portland, OR
@billintomahawk , @Aqua Puttana , @autostaretx , thanks for all the help!
I've also ordered the Dorman replacement connector. Will report back if it mates.
Also, it is possible to measure the resistance and see if it's abnormally high? I suspect this would not help if the high loads (think motor catches something or bearing seizure) were intermittent.
I too, would be very appreciative. Especially the carbon brush part.
I've also ordered the Dorman replacement connector. Will report back if it mates.
Also, it is possible to measure the resistance and see if it's abnormally high? I suspect this would not help if the high loads (think motor catches something or bearing seizure) were intermittent.
gilee
2006 Sprinter 2500 Camper
For lubricating the motor, I am Unable to open up the motor without breaking something or worried not able to put it back, so I didn't try. I opened up many motors before, but this one I cannot figure out how (without damaging it)
So I decided to clean it, and lubricate with wheel bearing grease from each end of the axle bearing area. I first use ~120PSI compressed air to blow it clean, then I connect the motor to power, and spend it. I use lower voltage to just get it to turn... maybe 60 or couple hundred rpm??
While turning, I apply wheel bearing grease to the end, while moving the motor facing up, so gravity pull the axle downward, exposing more for the grease to get inside.
For the other side, the Plastic blades are pressed in, so again, I don't want to risk damaging it, so I use a wire bended it into "J" shape, and put in some grease, and spin it... I keep repeating this and try to do it as much as possible. With power off, I try to spin the fan with my hand as fast as I can, and it does feel smoother each time I repeats it more times.
Then I remove the brushing, assuming it is never replaced, its over 200K already.
I did this twice, one from my previous sprinter, and I found this way is the easiest and best way to remove the clip that holding the spring and the brushings.
Just becareful, as they will crack and break.
I just ordered the cheapest one from ebay, $10 I think. it is longer, but its ok, I just cut them into right length, then file them into curve shape.
I wish I can provide more info on "Opening up the motor" but I doubt this motor even possible to be opened without permanent damage. if anyone did it before, please chime in. Thanks.
Incase you don't know how to take the motor out of the plastic housing, push into these 3 rubbers stopper, and the motor will pop/push/fall out.
Hope this helps guys!
So I decided to clean it, and lubricate with wheel bearing grease from each end of the axle bearing area. I first use ~120PSI compressed air to blow it clean, then I connect the motor to power, and spend it. I use lower voltage to just get it to turn... maybe 60 or couple hundred rpm??
While turning, I apply wheel bearing grease to the end, while moving the motor facing up, so gravity pull the axle downward, exposing more for the grease to get inside.
For the other side, the Plastic blades are pressed in, so again, I don't want to risk damaging it, so I use a wire bended it into "J" shape, and put in some grease, and spin it... I keep repeating this and try to do it as much as possible. With power off, I try to spin the fan with my hand as fast as I can, and it does feel smoother each time I repeats it more times.
Then I remove the brushing, assuming it is never replaced, its over 200K already.
I did this twice, one from my previous sprinter, and I found this way is the easiest and best way to remove the clip that holding the spring and the brushings.
Just becareful, as they will crack and break.
I just ordered the cheapest one from ebay, $10 I think. it is longer, but its ok, I just cut them into right length, then file them into curve shape.
I wish I can provide more info on "Opening up the motor" but I doubt this motor even possible to be opened without permanent damage. if anyone did it before, please chime in. Thanks.
Incase you don't know how to take the motor out of the plastic housing, push into these 3 rubbers stopper, and the motor will pop/push/fall out.
Hope this helps guys!
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