Blower Resistor

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jims-terrano

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Does anyone know if there’s a difference in the resistor for the blower between years? Reason being my 99 has stopped worked so I have a spare heater box from a later model so fitted the resistor from that but it’s a different size. The plug is the same and so is the fitting for the heater box. The later seems smaller and earlier is bigger, see the photo below. Have fitted it and it is working but if different it might blow this one too.
 

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If it fits the hole and the plug fits then it is just a modified later type, the main thing is it needs to fit the hole properly in order to maintain an air flow over it for cooling, Rick
 
I would say that they have changed the design to get more of the carbon resistance track up into the air flow, so as Rick says, it dissipates the heat and reduces the risk of burn out.
 
I changed my resistor and pollen filter late last year. Its seems to have burnt out again. Im guessing a blockage or flow problem causing it to overheat. Are there any culprit easy to access areas to check out or is it all tucked away behind the dash?
 
Does this symbol on the bottom of the image mean that there should be continuity between each of my resistor connection? Following the workshop manual as This relatively new resistor has failed i believe.

Have continuity on 3 of the 4 connections but no visible damage as far as i can tell.
 

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New resistor. Had some dirt on it but cleaned up.
 

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Firstly the symptoms of a blown resistor are that your heater fan/blower only works on number 4.
It’s normally the thermal cut out that corrodes and stops conducting current. I’ve just checked continuity between all four connectors on my faulty resistor and can confirm there is no continuity between them at all. Thinking logically there will be one output to the fan direct from the resistor and then three inputs from speed settings one to three on the switch with the fourth setting on the switch going direct to the fan. Effectively the resistor is dropping the voltage from 12v in three steps which slows the fan down.
 
Thanks Jim. Ive since had a read up on how they work. The symptoms you have described are what this newer resistor cured. I was surprised it only lasted 6 months at the most which lead me to look for something else occuring.

I will get a replacement ordered and see if maybe I have a blockage or air flow issue causing the resistor to over heat.
 
Have you changed pollen filter lately? This blocks and restricts air flow and then causes the resistor to overheat.

As a test but I hasten to add not a fix as it could effect safety you could bridge the thermal cut out with solder and a thin wire of some sort. This used to be a fix in the downloads section but it was decided that the thermal cut out is a safety device so the download was removed for obvious reasons. Personally I think temporarily bridging will prove if it is the resistor causing your problems.
 

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