@ quickbooks,

that setup will result in melting of the connector........
The heatsink for the resistor is too small!
Mount it to the body!

 

Well, as I said previously that is a concern of mine.

Spurred on, I made a quick test today. Note that most common auto wiring plugs are rated for 105 centigrade (224 F) service.

I backed the car into the driveway, turned on the a/c, popped the hood, and pulled up a chair to watch. Admittedly the test was short, only 15 minutes, but I did not notice an appreciable change in temperature after the first five minutes.

The resistor itself is hot, but not flaming hot. The tip top of the wiring harness bracket was hot to the touch, but allowed momentary finger contact without burning. The lower part of the bracket, where the wiring is attached, was in a normal temperature range that allowed continuous finger contact. Further, I had a cup of water and an eye dropper, and I occasionally dropped a drop of water onto the resistor. It did not sizzle, but evaporated slowly. The drop would remain on the resistor for a reasonable time. There was no noticeable temperature on the plastic plug itself.

For comparison, I carefully made the finger test elsewhere in the engine compartment. There is a plastic sensor/valve on the passenger side right in front of the motor mount with a two wire plug. It was noticeably hot to the same finger sense as my resistor mount. So, my resistor mount is comparable to other engine compartment electrics.

I will inspect it again after a hot day of city driving, but I think the arrangement is within heat limits. Note also that if the engine or environment is hot enough to trigger high speed fan, the resistor is cut out. So in very hot environments there should not be heat buildup on the resistor. Finally, recall that the original resistor is mounted in a plastic housing, and must issue the same heat for the same voltage drop.

I do notice an improvement in my a/c with the fan running. The supplied air is cooler than I remember last week, even when driving. Again with my hand, the radiator was cool, but the a/c cooler was hot. Clearly an idling car with a/c on needs a fan to cool the cabin.

p.s.
When I moved the car out to make this test, I heard this "pop pop pop" and I thought, ugh, I've just shorted out something under the hood. But the car seemed just fine. Then I discovered some bubble wrap had fallen on the floor and I had driven over it!

 

I used the same resistor, but built a heat sink from aluminum sheet stock. Works great. Will take pic soon.

 

I have a late '02 build with the low speed fan not working. Resistor is fried.
I read through this thread and unless I missed something, do I have an option other than just replacing the fan unit? Looks like finding/buying a resistor seprately is a problem, but I thought I would ask.



DrO any update on your "kits"?

 

Getting the resister is not a problem. But on the pre-04s you have to remove the fan to mount it. At that point the $80-120 for a new fan from Rock Auto or some other vendor makes sense. The fan from the Dealer is $225 and WAY overpriced.

///Rich

 

Yep, thanks. After sleeping on it, I decided to just buy the whole unit.

 

So last weekend I replaced the OEM fan with a TYC one from Rock Auto. I really wanted a Dorman 620-902 but that was backordered everywhere and frankly now that I have seen the TYC it looked identical to the OEM one and now is working fine in Artoo so saving $40 seems like the way to go.

Today I did some closer looking at the fan I replaced. My fan also had a sticking relay that required a whack sometimes to get the fan to shut off when the car gets turned off. I kept a 6" extension next to the seat for whenever that happened which was not very often but when it happened it was always inconvenient. I wanted to get a new relay and when I went to the dealer the #61360141229 was superseded and since I never saw the relay I thought I was out of luck as I thought the relay was big and black. But today I realized that the relay is the same as the new ones (after 3/03) and is on the fan instead of the fuse block which is good news. So I will get one of those and replace it on my bad fan.

You can also see that my low speed resister is clearly bad. What I intend to do is cut it out and solder on leads that I'll tape to the wires and bring out to the connector terminated with some R/C battery connectors I have around. Then if this TYC ever goes bad, I'll have this one all ready to go with a new relay ready to take the external resister I prepared when I thought it would work jumped at the connector.

One question. What is that little device that is in series with the resister? Chris, did you or anyone else measure that? I am wondering if the resister for the older, two plug fans, is rated differently which frankly would be my luck.

But I'll have a fan here when I need it with a new relay and tapped for the external resister. The motor seems to never go. And since these seem to go every 35,000 miles or so, in about two years I'll be slipping it in to see what happens if someone doesn't borrow it first.

Pictures of the fan relay and bad resister are attached.

Rich

 

I suspect the device in series with the resistor is either a diode (to stop back voltages) or a thermal fuse (to stop overheats)........
But as mine is still buried on the fan I can not check this.

 

That is what I was thinking. I am thinking diode as it looks to be different on both ends. But it doesn't look like any diode I have seen before.

I put this in the nothing is easy category and I'll do some readings when I get the chance.

///Rich

 

Rich,
Your factory resistor looks exactly like mine did before I installed the new one. As far as the sticking relay goes, I had the same problem you did. Ever so often the relay would stick and the fan would run after the engine was shut off. A quick tap on the relay would fix it temporarily. I did not replace this relay and thought I would address it when the time came. Since I have changed the resistor (over a month now) it hasn't stuck a single time.

I used to have to switch the A/C on if I was sitting in traffic, so that the fan would work. Any length of time spent this way would usually result in the relay sticking (at least 15-20% of the time). Since the resistor "upgrade" I have used the A/C the same amount, maybe more and haven't had a single problem. Just thought you might find this helpful.

Good luck,
Josh

 

cant post pics will re try

 

Hi, my low speed resistor also has failed I have just fitted the aftermarket resistor as per the chris.j.lamb fix I tried to screw it in the same position as chris, did but could not get my hands in, he must be a gynecologist as a day job . so i screwed it to the engine mount which acts as a smashing heat sink, I had two sizes of wire available one a bit thicker than stock and one a bit thinner my soldering Iron did not have enough power to solder the thick so I plumped for the thinner. and covered it in shrink sleeve. I cut the feed to the low speed fan "well you have to break eggs to make an omelet" stripped a section of the fast speed wire and tapped into it.

 

Beautiful. My guess is that this will never be a problem for you again. I am going to retrofit the fan I took out with a new relay and pigtails off the resistor. I don't ever want to buy another fan again either.

Rich

 

When I tested it after wiring up (before it was mounted) the resistor got too hot to touch within a minute, This resistor is designed to be mounted on a heat sink with compound.

 

I do have small hands.............

 

I considered mounting mine in that same spot, but had some vague concern about drilling holes in what appears to be cast aluminum.

 

As far as I know cast Aluminium is the ideal metal to drill and tap, after say a gearbox casing is cast it undergoes many such procedures, it is prone to cracking with a heavy impact like a sledge hammer blow etc.

 

Yes. When I say pigtails I am going to tap both ends of where the resister used to be. Run the wires along the path of the wires that are there already. Then terminate it with some battery connectors from an R/C truck.

I mounted the resister to the aluminum engine brace as in the picture and when the new one I have in there fails, I'll be ready to go.

Rich

 

Drilling and taping my brace to take 8-32 screws took only about a half hour. It was easy.

Rich

 

Well I knew everything was bigger and better in America but 8 screws! edit..oops 8-32nd of an inch sorry I'm too used to metric

 

I do suppose I could have used M4s but I had 8-32s in stainless that I wasn't using. And I would have had to buy the M4s in stainless.

Rich

PS-It's not bigger and better her. Mostly though it is cheaper as our government has an aversion to VAT or any other reasonable tax scheme to ensure social justice (please no flames). They are only interested in the rich and famous.

 

Slightly off topic talking about stainless, I am surprised how poor the quality of the fasteners and fittings are on the Mini, many of the nuts bolts and brackets have corroded, on inspection they seem to have either no plating or just lick of paint.

all the fittings on my 1980 Ford which I have had from new and has not been garaged are fine. I'm thinking to get a zinc plating kit off ebay,

 

I've just had an Idea, if you have just fitted a new fan and resistor assembly with pigtails, could you not wire up the aftermarket resistor as well, as it is in parallel the resistance would be the same and as the load is 77w each resistor would only be taking half that, then if one fails ( which will be unlikely as they are running cooler) the other automatically take over the full load, EDIT.. my mistake I have been informed, resistors in parallel reduces the resistance.

 

For those who can't find the wirewound resistor, I ordered mine on May from newark.com. They generally have them in stock.

http://www.newark.com/tyco-electroni...45?Ntt=16R5345

 

I'm not so sure about that. When resistors are connected in parallel their combined resistance is less than any of the individual resistances.

If I recall correctly, Rt = 1 / (1/R1 + 1/R2)

Assuming R1 and R2 = 0.47

Rt = 1 / (1 / 0.47) + (1 / 0.47) = 0.235