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Hi Guys,

I'm trying to find a blower resistor for my Series 1 Esprit. My car doesn't have a squirrel cage blower, instead it has a two speed blade fan welded directly onto the heater box. It has two wires running from the binnacle to the blower. One goes directly to the blower and the other goes through a resistor then to the blower. Does any one know what the resistance of this resistor is? I tried measuring it with an ohm meter but its so corroded I can't get a reliable reading and my meter wanders from 0 to 100 ohms. It looks like the one I have overheated and melted the wires running into it. I would like to replace it with a newer one that has a heat sink possibly from another car.

There are some pictures of the whole thing in this thread.

http://www.thelotusf...tor#entry368629

Picture attached.

Brian

post-13255-0-00605800-1344871797.jpg

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Nobody seems to know what this part is  :cry:

 

My car has a two speed blower, from the binnacle one wire goes straight to the blower, the other goes through the above resistor. I could be wrong but I think all S1s only have a two speed blower motor. 

 

Does any one know the resistance of their blower motor resistor? I'll be able to find a suitable replacement with that information.

 

Brian

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Not quite an answer to your problem but if you measure the current draw of your fan when on full speed (it might be on a label!) you could calculate the necessary size of the resistor needed to drop the voltage by what ever amount you wanted using Ohms Law.

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Looking at the photo, seems that the resistance is still intact and the terminals are your problem. Can you get a decent resistance reading from the element itself? I'd be inclined to drill out the rivets and clean up the ends of the element and the underside of the connections, then rivet it back together again. Bet it would work after that! Nuts and bolts would work just as well.... 

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Hey Guys,

 

Two good suggestions, I've already popped the rivets, so I'll try putting some new terminals to get a reading. I'd like to replace it with a more modern resistor with a heat sink as I think this guy heated up too much and melted the wires from the binnacle.

 

Brian 

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Alright so I've re-riveted the connectors to the resistor and have gotten a good resistance reading of 4Ohms. I figured I would re-install it and see if it still works. Sure enough the blower works nicely but I've definitely discovered the melted connector problem. This resistor gets HOT, after 30 seconds it was way too hot to hold so I turned it off.

 

Based on my math: 

 

I = V / R

3A = 12V / 4Ohm

 

P = I * V

36Watts = 3A * 12V

 

So I need a new resistor that can dissipate 36Watts at 4Ohms shouldn't be too hard to find.

 

Brian

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It's not quite that simple I'm afraid. You need to measure the resistance of the field windings and allow for that too. Also, you need to allow more than 12 volts as the voltage will be higher with the engine running. Once you've calculated your resistor wattage you then should allow a safety factor, probably 2 times is sufficient since a lot of high power resistors can take transient overloads of up to 10 times.

 

The resistor will get hot when in use, they are often mounted in the airflow to cool them.

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Hi Guys,

 

I've sourced a 100watt 4ohm resistor with a nice big heat sink. I wish I'd thought of placing it in the air flow before I re-installed the airbox. I'm thinking of mounting it onto the cross beam under the dash to help dissipate the heat, its a nice big piece of metal so it should be able to dissipate the resistors temperature. I guess the only way to tell for sure is to mount it and run it for a while and see just how hot it gets.

 

Brian 

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