dropping resistor repair 3,8/96

[tums]

the dropping resistor seems to be a very weak spot. I took off the heads - to find they were perfectly ok - the leak was the gasket (or sealant of the studs) of the waterpump and the rest of the problem a corroded dropping resistor. It looked exactly like wiswinds - the foto a duplicate.

Now what to do if none is available (in time)? Try to repair it. Believe me, the better option is to buy one, however there are some reasons to repair:
1. you are not willing to wait
2. you are not willing to have the same problem in the next 50 years
3. youre not finding a replacement
4. somehow there should be a way to fix it ...

The resistor got around 1 ohm, the exact value should not be an issue as the fans may run a little faster or slower - so what.
It should be made of special material (incluiding nickel) as the usual metal will not have enough resistance. Now the copper is bonded to this surface and eventually will corrode, especially as heat and humidity will help.
The body holding it is ceramic and the inside should be cement. If you are cautious with a hard steelneedle and a small hammer you will get the connection from wire to resistor free.
You have to clean the tip of the resistor(band) to bare metal. soldering will not help because of the type of the material - what you will need is hard-soldering with flux. If done correctly the brass will "creep" on the metal - it should not "sit" on it (it will get cherry-red glowing!).
You will have to dissassamble the connector since you will have to do the same to the wires and the creeping heat may destroy the plastic. It is simple, with a small hook pull out the inner plastic, then the red silicone clot at the back, now releasing the plastic-clamp inside you pull out the wires.
Drill the wires, as they will spread when heated and put a drop of brass on them. Done this put them on the spot on the resistor and heat both untill it combines.
Finally take epoxy compound and fix the connection (take care: not the resistor-metal, which will get hot) to the (most probably broken) ceramic body. It might smell, but should work.
If I am not mistaken that should last a little longer than the original.
I have pics about this, but no idea where to put them.

If you ask if I am crazy: going 2000 miles pulling a caravan through mountains with a cooking transmission (actually: cavitating) not knowing what the heck is going on - you want ot make shure - not again.

[Selectron]

Unfortunately, we know neither the resistance value nor the power rating of that resistor. If we knew them then I'd suggest replacing it with an aluminium-bodied wirewound, mounted on a metal heatsink - something like this:



I think I remember 12Ounce mentioning aluminium wirewounds so maybe he was saying the same thing, or maybe it was something else.

I'd be curious to see the photos if you can upload them. If you click on Post Reply (not Quick Reply) you will see an option to Attach Files, and if you click on Manage Attachments then that allows you to upload them.

Or you can do quick uploads at www.imageshack.us - no registration required, or you can get a free photo hosting account at www.photobucket.com - registration required but it gives you more control over your photos - you can create albums, set the account to publically-viewable or not, etc.

[tums]

I got the same idea - basicly any common glazed (emailled) wire-resistor would do. I measured app 1 ohm with a digital meter what is fair enough - it is not the NASA but a simple "dropping" design, the worst that could happen the fans running a little faster or slower.

Doing some simple math the maximum power to sustain would be (on a short) 14V / 1 ohm comes to 14 amps x 14 V = roughly 200 watts. As there is a fuse with 40 amps and as the design looks quiete "strong" it should be expected for the worst case.

However: this 1 ohm was seemingly with some corrosion around. I now measured again for curiosity and found less then 0.2 ohms - for one the hard-soldering seems to work, for another: you should not use a resistor not designed for this pupose. Reason can be that the amp-flow and corresponding heat in the resistor follow a certain scheme, depending on the construction. That means that the resistor "working" has another value (due to its heating up) so to substitute a reasonable value you would have to measure the voltage-drop on the system working and calculate the resistance, then find another resistor giving the same value (at this condition).

Now there are some on the market, and - they are not "cheap" either: but if not "out and in" plus spending money plus fumbling around then the overall situation is like waiting, spending, changing connectors, not getting a better result in the end

and in the background the welding equippment is lurking

well, actually repairing cost me less time then the internet alone.
Thanks for the hint with the files, " .... I'll do my best". Hope, here they come:

Note: in pic 2 the only connection left is a fibre - if you measure that "cold" it will give the correct resistance - however under load it will heat up, gain resistance and thus behave completely different

[Selectron]

You've made a neat job of that - much tidier than I expected. If I remember correctly the replacements are a ridiculous price, but what you have there will probably outlast a replacement anyway so I reckon it was time well-spent. Thanks for letting us see the photos.

[tums]

Thanks for the flowers

[wiswind]

I have mentioned before.....I suspect that there are a lot of folks driving around with that part not working....NO low speed fan operation.
I personally believe that this is the hardest on the transmission.
When in stop and go traffic......I like to put the A/C on to keep the radiator fans on at low speed.....keeping the motor at a more constant coolant temperature and keeping the transmission cooler by keeping air moving through the auxillary transmission fluid cooler.....as well as keeping the in-radiator transmission fluid cooler at a lower temprature.
If you have no low speed radiator fan function.....then it is just plain not good.

My Sienna seems to run the fans ONLY when the A/C compressor is on.......which is still good....but I like the windstar's staying on better.
I keep thinking that some day I am going to put a big toggle switch on the dashboard.....and be able to put those fans ON and keep them ON when I want them on.

[onit]

Is that the one that controls the fan to come on and off? if so i had that replaced under warranty within the first two years that i owned the car. I had taken it in for them to check leaking coolant and the temp gauge going to the high side. The tech had told me it was a thermistor. Is that what this part is called? It hasn't given me any problems since. The one thing i have done since i had that climbing temp gauge problem is always glance at the temp gauge and also check on a daily basis the coolant level.

[tums]

It does not control the fan on/off but slow/fast - it is nothing more then a bottleneck for the amperes to creep through before doing their work turning the fan.

If it is corroded (or at the brink of failing) it means that bottleneck is getting tighter, the fan slower and the average temperatur higher (less cooling). There may be other symptoms depending from the actual state of failing.

You could call it a thermistor since it should change resistance - but actually I would call it a resistor by function (as Ford does - see title).

[wiswind]

It is a resistor......stays the same basic value.
The thing is......when the PCM commands the low speed fan operation......you will have NO fan.....
You will have fan operation when high speed fan operation is called for.

So....in stop and go traffic....with the A/C on.....you will have hot condensor coils on the front of the radiator......and no radiator fan......except when high speed function is called for.
HOWEVER.......with a good dropping resistor......in stop and go traffic with the A/C on......your radiator fans will be on at LOW speed and stay on.......keeping your coolant at a more consistant and lower temperature......AND your transmission fluid cooler.