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Old 1st May 2017, 08:41   #1
Mike Trident
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Default Gold Resistor exploded?

I fitted a new gold resistor to the fan about 6 weeks ago, and everything was fine until yesterday.

I fitted my recently aquired front bumper yesterday morning. The bumper came with all the lights and temp sensor fitted, so I figured that before I replaced all the bolts and fittings I would check all the lights were working. I started the engine and checked the indicators were flashing, yes! small spot lights, yes! headlights, yes! All good to go!

(I had the bonnet open) Out of the blue I saw smoke coming up from from the left side radiator area, very quickly followed by a pop noise. I quickly turned off the engine and was ready to get a bucket of water expecting flames!

The smoke had that electrical smell, and slowly cleared. I figured I knew what it was, so got my torch and shone it into the front grill at the resistor. Yes, it was the resistor, one of the ends looks to have blown out of the gold case.

I am at a loss as to what caused it. I am guessing the fan didn't start. Now I know that the resistor MUST have the fan blowing on it because it gets hot very very quickly as i found out when I was fitting it just a few weeks ago.

The only thing that I can think of is that when the temp sensor has been disconnected the system has to re-set. I do remember when starting the engine that the gauge in the car was showing -9 deg, but I didn't think anything about it as it had done the same last time the bumper was off. Did the -9 deg cause the fan not to start? I can't remember if when I fitted the resistor if I turned on the air-con demist which turned on the fan straight away.

I have ordered a new gold resistor, but I just wondered if anyone else has had a similar experience.
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Old 1st May 2017, 09:15   #2
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Faulty resistor, or, the fan was jammed or has failed. No need to look any further. The resistor regulates the current (well limits it is a more accurate description), to the fan. If the fan runs it will cool the resistor. If the fan motor is short circuit or stuck it will draw more current, overloading the resistor.
Check the fan, if its ok just fit another (better quallity?) resistor.
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Old 1st May 2017, 09:34   #3
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My third one went last week, also popped. Had one go 3 years ago that popped , set light to the wd40 I had sprayed onto the bonnet catch and got sucked into the air filter. That also set light and melted the air intake😳. First one was a eBay unit, second replacement not. Fan was working.
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Old 1st May 2017, 09:54   #4
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Quote:
Originally Posted by Mike Trident View Post
I fitted a new gold resistor to the fan about 6 weeks ago and everything was fine until yesterday.
It suggests to me that the failure is associated with the recent work around the front end of the car. I think six weeks of normal operation would indicate the fan system was OK before the bumper stripdown. Anything that impares fan rotation will short out the circuit, so there's a strong possibility that the blades were not as clear/free as they might have been.

I wonder why the 80amp fusible link in the under bonnect fuse box didn't blow first? Isn't it supposed to prevent this? I've suggested before that this fuse is too big. To support the argument, I've replaced mine with a smaller fuse. My fan is now running perfectly well with a 40amp link despite 'calculations' suggesting the startup current needs the 80amp fuse. I'd suggest the fan wiring will ignite before an 80amp fuse gives in. To me, the size of the wiring looks more like 35-40amp.

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Old 1st May 2017, 09:56   #5
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Are the GOLD RESISTORS that are failing been supplied via traders on the Forum or were they "ebay" specials ?
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Old 1st May 2017, 10:02   #6
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I too had one fail last year. Had been on the car for about 2 - 3 years. one end had blown out. mine came from a trader here as did the replacement. could water have gotten into the resistor?

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Old 1st May 2017, 10:04   #7
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Quote:
Originally Posted by steve-45 View Post
Are the GOLD RESISTORS that are failing been supplied via traders on the Forum or were they "ebay" specials ?
From the three or four events I've read about on the forum, they were bought from both forum traders and from ebay. I recall Jules reporting a 2-3 per thousand failure rate. Any resistors imported from China are obviously not recommended.

Resistor Smoke Signals: http://www.the75andztclub.co.uk/foru...d.php?t=181368

TC

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Old 1st May 2017, 10:15   #8
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Originally Posted by macafee2 View Post
Could water have gotten into the resistor?
It's been suggested as a cause, but i don't buy it myself. In my opinion, the underlying cause is uncontrollable overheating, which suggests insufficient cooling and/or current overload.

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Old 1st May 2017, 10:39   #9
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Quote:
could water have gotten into the resistor?

Quote:
Quote:
Originally Posted by T-Cut View Post
It's been suggested as a cause, but i don't buy it myself. In my opinion, the underlying cause is uncontrollable overheating, which suggests insufficient cooling and/or current overload.

TC
I would say yes myself if the join to the resistor as not been heat shrank tight, it is always best to make sure the heat shrink is pushed fully home up against the wall of the resistor.
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Old 1st May 2017, 10:54   #10
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Quote:
Originally Posted by Arctic View Post
I would say yes myself if the join to the resistor as not been heat shrank tight, it is always best to make sure the heat shrink is pushed fully home up against the wall of the resistor.
It's a worthwhile precaution, but there's no way to demonstrate how much it contributes to resistor longevity. These failures happen so infrequently, it's just as likely to be within normal manufacturing tolerance. Everything has a failure rate. Jules has said that 0.3% or so of his resistors fail, so it's pretty rare. So, when it does happen it attracts a lot of attention and invites various theories about the cause.

I'm more concerned about the lack of fuse protection. It's obvious that the 80amp fusible link in the motor supply circuit isn't doing what it should.

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