Radiator Fan Resistor - Alfa Romeo Forum
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(Post Link) post #1 of 3 Old 12-12-09 Thread Starter
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Radiator Fan Resistor

I've got a phase 1 spider with AC, it has 2 fan resistors mounted in the fan cowling. Both are in a right state with burnt out connections. I went to Alfa for replacements but they were 50 each, bit pricey for me. It's a common problem as Alfa told me the design has changed.

I went to a scrappy today and had about 4 which were all shot. I did manage to find one that looks like new from a 166. It's a newer design. I noticed the phase 2 TS engine cars only have the one sensor rather than the 2.

Can I fit just the one resistor and splice the 2 pairs of wires into it? Why are there 2, is it to kick in the fans at different temperatures?
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Those resistors are for the low/first speed of the fans, they are connected in series with the fans and one resistor per fan. The fans are switched on/off by a bi-thermal switch in the bottom of the radiator; first thermal switch point powers the fans through those resitors (low/first speed), second thermal switch point powers the fans directly for high speed.

The two fans with the two resitors are wired in parrallel, so if one resistor fails the second one will still pass current to both fans, so you do not need to splice the wires. There are just two to give the fans a certain speed, if both fans run through one resistor they will spin slower (2 resistors in parrallel = less resistance = higher fan speed).

The resitors are pretty low resistance (<1 Ohm), I think you can read that value on the side -so if the 166 resistor reads the same value, just use it. Even if it's not 100% the same you could use it, the fans will than spin somewhat slower on low speed.

What I've seen with my resistors is that the resistor's internal thermal fuse blew; if you look in between the plastic bit and the ceramic bit, you can see that fuse. So resistor itself was fine, just the 2ct thermal fuse blew. I just bypassed that fuse, works fine ever since. I don't see the benefit of that thermal fuse there, especially as the second speed of the fans bypasses the resistors completely.


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Last edited by SpeakerDocktor; 13-12-09 at 06:43.
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(Post Link) post #3 of 3 Old 13-12-09 Thread Starter
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Great reply, thanks for your help.
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fan , radiator , resistor

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