Low Speed Fan Resistor - we need solution
#703
#704
Ok gang, could use a little help here. I ordered what I thought was the right part from Mouser: 284-HS100-47F, PWR RES 100w 47 1%, Arcol wirewound resistor. http://www.mouser.com/ProductDetail/...kSjPXYqw%3d%3d
So, got everything wired up, it's not pretty but it'll do for now, started the car, turned on the AC, high speed fan's working, but no low. Granted it's warm here today, but still, no low. Had a voltage test light, there's voltage going from the car-side low speed wire to the resistor, and through it with no lead on the end, but once I connect the fan-side low speed wire to the resistor to complete the circuit, it drops to such a low amount, that nothing happens (very low/dim test light).
Can someone verify that I bought the right part, and shed any thoughts on what might be going on? I'm also using 12G wire all around.
Thanks in advance!
So I know it's getting power, but it seems like the resistor is diluting it too much.
So, got everything wired up, it's not pretty but it'll do for now, started the car, turned on the AC, high speed fan's working, but no low. Granted it's warm here today, but still, no low. Had a voltage test light, there's voltage going from the car-side low speed wire to the resistor, and through it with no lead on the end, but once I connect the fan-side low speed wire to the resistor to complete the circuit, it drops to such a low amount, that nothing happens (very low/dim test light).
Can someone verify that I bought the right part, and shed any thoughts on what might be going on? I'm also using 12G wire all around.
Thanks in advance!
So I know it's getting power, but it seems like the resistor is diluting it too much.
#707
Read through most of this thread and I have not found the answer to my question.
Is there a fix for the early model with the 2 wiring harnesses that does not require removing the fan? From what I have read the resister fix that works on the late model cars will not work on the early models with the 2 wiring harnesses on the fan, is this true?
Is there a fix for the early model with the 2 wiring harnesses that does not require removing the fan? From what I have read the resister fix that works on the late model cars will not work on the early models with the 2 wiring harnesses on the fan, is this true?
#708
This weekend I replaced the radiator, thermostat & housing, flushed the system & wired in the resisitor.
This shows where I mounted the resistor using only one screw to minimise damage, I also left as much of the resistor suspended in air as possible to avoid dissipating heat into the body, the resistor is not touching the loom as it appears to in the photo.
This shows where I mounted the resistor using only one screw to minimise damage, I also left as much of the resistor suspended in air as possible to avoid dissipating heat into the body, the resistor is not touching the loom as it appears to in the photo.
#709
The purpose of the metal housing of the resistor is to dissipate heat caused by current flow. It is intended that it be mounted to a larger metal surface. You really want to dissipate heat into the car frame, so as not to burn up the resistor. In the electronics business we call that a heat sink.
I hear you, but given that the resistor is contained within it's own Aluminium heat sink I don't envisage any problems. There is enough of the heat sink in contact with the chassis to dissipate heat, probably about 50%.
Also the climatic differences between Britain and SoCal mean the fan is seldom in action anyway.
Maybe BMW should have used your logic when they suspended/exposed the original and rather fragile resistor in an air dam!
Aaron.
Last edited by vwgillybilly; 07-09-2012 at 02:13 AM.
#710
Unfortunately for those w/ 2 plugs, resistor must be wired onto the terminals of the old shot 1 inside the fan. The difference is the relay wiring route. I dunno if anyone has extracted that known-to-stick relay inside & relocated outside for easier access & troubleshooting. I'd definitely wanna try to once I'd need this mod.....at same time, testing that C4 looking concoction of a resistor(in the pic above) from a good friend.
#711
#712
Has anyone tried using two .68 ohm resistors in parallel instead of a single .33 ohm resistor in series?
Lower current through each resistor would be less heat. You also get the stock .34 ohms as the final resistance.
At Mouser:
http://ph.mouser.com/ProductDetail/A...JylgtxTg%3d%3d
On eBay:
http://www.ebay.com/itm/150684453740...#ht_760wt_1163
Maybe overkill, but maybe not, considering how hot some of your resistors are getting...
Lower current through each resistor would be less heat. You also get the stock .34 ohms as the final resistance.
At Mouser:
http://ph.mouser.com/ProductDetail/A...JylgtxTg%3d%3d
On eBay:
http://www.ebay.com/itm/150684453740...#ht_760wt_1163
Maybe overkill, but maybe not, considering how hot some of your resistors are getting...
Last edited by gknorr; 07-10-2012 at 09:59 AM. Reason: Fixed eBay link to .68 ohm resistor (was a 68 ohm resistor!)
#713
Has anyone tried using two .68 ohm resistors in parallel instead of a single .33 ohm resistor in series?
Lower current through each resistor would be less heat. You also get the stock .34 ohms as the final resistance.
At Mouser:
http://ph.mouser.com/ProductDetail/A...JylgtxTg%3d%3d
On eBay:
http://www.ebay.com/itm/68-Ohm-68R-1...#ht_760wt_1111
Maybe overkill, but maybe not, considering how hot some of your resistors are getting...
Lower current through each resistor would be less heat. You also get the stock .34 ohms as the final resistance.
At Mouser:
http://ph.mouser.com/ProductDetail/A...JylgtxTg%3d%3d
On eBay:
http://www.ebay.com/itm/68-Ohm-68R-1...#ht_760wt_1111
Maybe overkill, but maybe not, considering how hot some of your resistors are getting...
#716
#717
#718
http://www.arcolresistors.com/wp-con...S-10-05.45.pdf
Note that the heat dissipation rating is much less if there is no heat sink -- e.g. 100W on heat sink goes to 30W no heat sink. The verbal description of this in the data sheet is:
"the resistor must be mounted on a heat sink of correct thermal resistance for the power being dissipated."
#719
Hey folks - someone must be able to figure out a cost-effective DIY repair for the prone-to-fail low speed fan resistor. Mine has now failed, but I sure don't want to spend $200+ just for parts, assuming I can complete the replacement myself, since I'm sure that eventually someone is going to determine that its a $5.00 part that is the source of this grief. The next person to have their unit replaced PLEASE save the old one; I'll pay to have it shipped to me and I'll see what I can do.
#720
The mouser resistor is better, because it has a good heatsink for better cooling possibilities. BTW, the original design seems to rely on air flow by the fan for cooling. That's almost a suicide pack.
I am surprised that no one has simply tried a better design from scratch. Instead of using a resistor to step down the voltage, use a switching regulator, with an input of 12v and an output of, what, 6v? The ones I use everyday can easily handle 15 amps.
#721
#722
#723
#724
For the earlier design, this should be it:
http://wds.spaghetticoder.org/en/svg...5989.svg?m=r50
http://wds.spaghetticoder.org/en/svg...5989.svg?m=r50
Here are the three that I know about: