Okay so the resistor bank goes bad on my crossfire, needed a little heat and no fan? Let the car sit and it's dead the next day because the fan kicked on in the off position with the fan. Look at the print and the fan is wired hot all the time from the battery? Why did they do this knowing the bank could short out at any time? I guess in most cases the fan just wouldn't work but mine shorted where it don't shut down. Just thought Id mention it.

 

They did that because in order to switch battery off to EVERYTHING, you'd need a huge relay or many smaller relays - and relays are high failure items themselves.
Going solid state is way cheaper and, overall, more reliable.

 

The fan is wired to battery B+ because of the REST feature, the thing that uses residual heat energy from the engine to keep the interior warm while you are in the bar ( pub ) having the after work toddy.

 

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REST also helps when broken down in the most extreme cold (hopefully in time for a rescue?). Although I would agree keeping the car warm while having that ONE 'on the way home' stress relief. LOL


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I've been wondering for awhile why Residual Engine Heat Utilization is abbreviated REST. I couldn't find it in the forum.
The best I can find is the German word: Restwärmenutzung which according to google translate means "Use of residual heat".
Maybe Viper-666 can help with the German language.

 

Well, learned something new once again. Thanks all for the response!

 

Does this sentence really say what happened or is it just an assumption? The battery and resistor was OK when starting the car so the resistor had to fail between starting the car and before the heater was turned on, or am I missing something?

 

Okay, here is the scenerio. Went to start the car the next morning, the battery was completely dead. Hooked up one of those battery starters and immediately the fan came on with the fan switch in the off position. Apparently internally the resistor shorted to ground and the fan was energized thus draining the battery overnite with the ignition off.

 

Not quite Dave... The regulator had to fail before he let the car sit, not at startup.
It sounds to me like the 'resistor' <Dammit, it's a regulator, not a resistor> failed while the car was running the previous time. When he shut the car off, he did not notice that the fan kept running, which is certainly possible. This is all conceivable.

The act of putting the top up or down, particularly with the engine not running, can also zap the fan regulator. My battery was over four years old (violated my own four year rule, you'd think I'd listen to my own advice), back in 2015. I tried to put the top up without starting the car, and zapped my seat belt module. Running old batteries and/or cycling the top without the engine running can take out modules in the car. I still think some SKREEMS die due to this cause. And don't get me started on those damn "battery tenders"...