An Idea to Solve the Blower Resistor Problem

[argentcorvid]

After buying 2 Resistors in a week (one has been blown for 4 years, the other this week), I decided that I don't want to do it again.

I was thinking that I could use one of the burned out boards, wire a few much beefier resistors to it, and just let it hang from under the dash. I know these things get HOT, and I'd probably end up putting a big heatsink on it too.

The thing is though, the new replacement module that I have seems to have all 5 of the pins shorted together. Can someone with easy access check this for me? It seems kind of dumb to have something like this where everything is shorted together.

when I get this done, I will have pictures & instructions to share with the group :)

[SE2000]

You don't want to do that imo. The blower cools the resistor. Having it hang will cause it to burn out quicker. I don't think there is enough clearence to have larger resistors and install it.
I have 2 GA's and they both have had their resistors replaced years ago. The trick is to get the newest revision from the dealer. The aftermarket one are based on the earlier ones

[argentcorvid]

Originally posted by SE2000
You don't want to do that imo. The blower cools the resistor. Having it hang will cause it to burn out quicker. I don't think there is enough clearence to have larger resistors and install it.
I have 2 GA's and they both have had their resistors replaced years ago. The trick is to get the newest revision from the dealer. The aftermarket one are based on the earlier ones

Regarding the heat issue, That would be why I would rig a heatsink (maybe with fan) on to it. I am not going to put it back in the hole where it is supposed to go, because none of the tools I have will fit where the other screw is up against the firewall, so I left the original one in there.

Who knows, I might even go fancy and decide to put the whole thing in a box!

I probably won't be getting rid of this car until it dies, so it doesn't really matter to me what modifications I make to the car.

[swapped]

honestly if my resistor dies again i'm going to do that. for the resistors to heat up less you could use several resistors in parallel then combine several of those in series

X--------/\/\/\/---------X--------/\/\/\/---------X--------/\/\/\/---------X
X--------/\/\/\/---------X--------/\/\/\/---------X--------/\/\/\/---------X
X--------/\/\/\/---------X--------/\/\/\/---------X--------/\/\/\/---------X

where X's are combine them together

if you wanted a 100k resistance, you would use 9 100k resistors in the above configuration. 3 100k's in parallel will give you a 33K resistance, so make 3 of those an then connect them in series and you get 100K but now instead of 1 resistor dissipating the power, its distributed across 9 resistors.......

at least thats how i think i would do it

[SE2000]

I know it was for display purposes but your resistance will actually be pretty low. Your wattage will have to be pretty high though.

I installed my replacements 4 years ago, they are still working. For the 99+, it's a 15 min job doing your second one with the right tools. I had no problem doing it and I'm not spring chicken. The part was 20 something bucks. How much will your parts cost? And having to stick a box in the small footwell. I've built many a project and unless you're using recycled parts, it gets expensive.

[argentcorvid]

this will be done mostly with recycled stuff. the heat sink especially; its an old computer one.

I've already blown $60 bucks on the stupid resistor modules ($30 each). maybe I'll just add a heatsink to the back of the module, Who knows. I'm just collecting info right now.

so back to the actual question, I'm looking for the resistance values, pin-to-pin, of the module. For the one I have right now, which just came out of the box, all 5 pins seem to be shorted together (I checked with a multi-meter). Is this the way it is supposed to be?

[SE2000]

Are you sure they are shorted. Yes 1 side is tied together but the other side should show resistance. It will be very low so short your leads to get see what it reads and then across the resistors

[argentcorvid]

ok. its not a dead short.

a-b=2.6 ohm
a-c=1.1
a-d=0.6
a-e=0.6

assuming a cheapie multimeter, does this sound right?

the really weird thing is that it doesn't look like any of the traces cross.

so i'm assuming a we have either a dc shunt or compound motor?

[SE2000]

Those value seem close. you have to remember is that you are basing you values against the motors resistance which is low.
A potentiometer and a large src may be more plausible.
Since GM has FIXED this problem, the ugly contraption to get around this and most people inabilty to manufacture, I doubt anyone will be truly interested in duplicating your idea.
The concept is good and if it was not resolved, I'd think it would be worth persueing

[argentcorvid]

The reason I was thinking of doing this, is that just about anything would have better heat dissipation than some wire traces on a circuit board.

BTW, I'm pretty sure that I got the new style module both times. If the how-to on this site is right, the short green one is the old style, and the new style is a longer, dark color. The ones I have are a dark brownish color with 4 silicone things on it. On the first blown module I tried removing the silicone, and it looks like there is just solder underneath. So I assume that the actual resistance is from the traces?

[argentcorvid]

I just checked how the speed switch connects to the resistor module.
if you are looking at the plug with the clip facing up, this is what I got:


__________T__________
| X X X X X |
---------------------
Gnd 4 2 1 3


The voltage on the pin when the switch was in the corresponding position was ~14.5 vdc. The others read 0 v.

The pin labled 'E' on the resistor module is Ground.
Then I measured the resistance of my new module and got this:

pin | spd | res
A | 3 | 0.7
B | 1 | 3.1
C | 2 | 1.6
D | 4 | 0.3
Speed 5 bypasses the resistor module.

using Ohms Law V=IR -> I=V/R:

on speed 1, there is about 4.6 Amps going through the resistor.
on speed 4, there is about 48 Amps! :???:
That doesn't sound right.

I also figured out why the pins looked shorted together. I was using the wrong pin as negative. The way this thing works is, on speed setting #1, the current goes through all of the traces on the board. The engineers who built this thing have some of the traces connected together at the pins, but only pin E and one other are connected at once. so, it is basically just using the resistance of the copper traces on the board.

Oh well. maybe I'll just J-B weld a spare heatsink i have laying around to it. that will help, I bet.

[SE2000]

You're not adding in the motor resistance. They are in series. The power drop across the resistor reduces power to t he motor, hence, the motor spins slower.
Did your resistors come from the dealer? If not, I don't care where they came from, you cannot expect them to last.
If they are dealer parts, what part #'s did you get?

[AaronGAGT]

Are you guys getting the new design resistors??? Because I've had mine on for like 3 years now.

[pokesmot]

it is possible to use high wattage resistors, and ive even thought about doing this myself; however you will need to determine the resistance value for each fan speed setting, IIRC you will only need 4 resistors.

http://www.hifi-writer.com/blog/graphics/dale-nh250.jpg

Load resistors are capable of withstanding large amounts of current passing through them, and they even have a heatsink design to help dissipate the heat.

[tenspeed]

I don't use position one and two. My fan is either off or on three and above.

I'm at 70,000 miles with the original.

[argentcorvid]

pokesmot:
Yeah, that's exactly what I was thinking. or even a normal 1/4 watt resistor. It HAS to be better than what it has now.

[SE2000]

20 amp fuse for blower. 1/4w resistor. Not likely to last long

[AaronGAGT]

maybe your car has something else wrong with it that it keeps blowing that. I'd say 95% of people that fix it once, don't usually have to do it again. Especially within a week!!!!! You don't need to do all this pointless work with heatsinks, different resistors, etc. Mass overkill.

[SE2000]

Here is a link to someone who took pictures of the normal process

http://www.gaownersclub.com/forum/showthread.php?s=&threadid=42552

[argentcorvid]

SE2000: Yeah you're probably right about the 1/4 watt resistors, but what about the boards? How many watts are they rated for? A good deal less than (amps^2 * 3.1 ohms), apparently.

I was just screwing around, and found out that the four things under the silicone are just solder. I got out my Soldering iron, re-soldered the connection that blew on the first replacement board I had. I will try it out tomorrow. The resulting resistances are the same as the new one I have. I don't know for sure why they chose to do it this way, but maybe the solder blobs are supposed to act as a fuse?

[argentcorvid]

AaronGAGT: It had crossed my mind, that something else might be wrong. I know other people here have had problems with water coming through the firewall and getting into the motor. I haven't noticed that there is any water coming into the car (but it could be a small leak I guess).

But this problem has got me hooked, and now I have to figure this out.

[SE2000]

Originally posted by argentcorvid
SE2000: Yeah you're probably right about the 1/4 watt resistors, but what about the boards? How many watts are they rated for? A good deal less than (amps^2 * 3.1 ohms), apparently.

I was just screwing around, and found out that the four things under the silicone are just solder. I got out my Soldering iron, re-soldered the connection that blew on the first replacement board I had. I will try it out tomorrow. The resulting resistances are the same as the new one I have. I don't know for sure why they chose to do it this way, but maybe the solder blobs are supposed to act as a fuse?

Solder is not suppose to be a fuse. The fuse is a fuse.
In the picture in the link is 2 different resistors. The new longer one is longer to put the resistors further into the airflow cooling them down. If both yours are not the longer type, then EXPECT them to blow.
The ice jams blow the fuse. It can take out the resistor.
The lower the fan speed, the more power that must be dissapated across the resistor. Any obstruction will cause more current in the resistor. People seem to use the lower fan speed for the majority of the time. These factors explain why the resistors blew out.
GM got up to revision 5 to get it right. If you're are not both rev. 5, you are wasting your time. If you had 2 rev. 5 and both went bad, you might have another problem which is a bad motor. You never said fuses were blowing so you do not have ice build up.
If you want to play with this, be my guest. Wanting to share your solution is nice. But I don't think anyone would bother implimenting something like this.
If you want to design a circuit that people would like, my suggestion would be in lighting control.

[pokesmot]

considering resistors cost practically nothing, and if there are people out there who are somewhat electronically inclined; I think this mod would be a good idea.

New GM ACDelco resistors run for around $20 and aren't exactly reliable... but if there are people inclined to make their own blower resistors it will save them money (at the cost of some spare time). $20 as a pose to $4 in parts. thats $16 that can be spent on fixing some other broken part of the GA :D

GM obviously made the resistors cheap... which is why there are so many problems with them in the first place. If you do decide to go ahead with this, post some info and pictures if possible that way anyone else who might be interested can find it.

Although it is apparent many users on this forum don't want to hear about this, I for one would!

[argentcorvid]

A little bit of an update:

Resoldering the blobs on the board allows the module to work for about 10 minutes, before blowing again. I'm pretty sure it's still shoddy construction/design, because using the same module each time, the open occurs in the same place.

I took the car in to the dealer last week to have the blower motor (and another module!) replaced. The module lasted all of 1 day before it let its magic smoke out. I am definitely going the 'make it yourself' route now.

And from a couple of electrical engineers I spoke to, it is plausible that the solder blobs are on there as a fusible link.