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Discussion Starter #1
Originally I hadn't plan on using the fan relay, but after reading about fried switches the other day I changed my mind. I wired it up tonight and although everything appears to work fine I have a novice question about the proper way to wire this relay. According to the Manual :eek: the terminal marked 87 is suppose to be wired directly to a 12 volt power source. My question is does it matter if this source is always "hot" like where the positive cable from the battery connects to the starter solinoid :confused: My concern is that the relay might somehow drain the battery if its wired like this. :( Thanks in advance for any guidance.
 

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Gil, as Ryan says you should be fine.

ALWAYS HOT allows you to run the fan motor with the ignition off.......but I've never done that for a cooldown. It will work fine using the switched ignition as a source too.

You do turn off the Master Disconnect when you park it, right? That should kill everything except the computer, clock, radio memory.
 

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Discussion Starter #4
Thanks for the input. I do turn the master disconnect off when I park it, but since I'm jumping the master disconnect switch with a section of wire with a 10AMP automatically resettting circuit breaker (to keep power to the computer, clock & radio) I was still worried about a potential drain on the battery.
 

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I experienced the opposite of what's mentioned above. I had my relay power wired to an always hot fuse off the fuse panel. I also had a keep alive jumper on my battery kill switch. With the car off and the kill switch in kill mode, the battery would drain.

Once I changed that connection to the relay to a switched fuse, the battery drain problem went away.

There's really no advantage from an engine cooling point of view to run the fan after the car is off...unless you have an electric water pump. The fan would cool the water in the radiator, but that water won't make it into the engine since the water pump isn't moving. I guess it could have a margin impact on cooling the motor by circulating air through the engine bay...but I don't think it would justify dealing with a dead battery.
 

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I agree with Dan - no point having the fan stuff energized with the master disconnect off. I have a temperature switch in addition to a manual override for the fan, and if that switch failed it could draw down the battery fairly quick.

Dennis B.
 

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Discussion Starter #7
Okay, it's two votes each. Anybody want to offer a tie breaker :confused:
 

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Gil

Run the relay in series with your switch. The switch will activate the relay. The relay coil is very low current draw so the switch will not fry. The relay contact take the load.

You can use the battery power for this. You flip the switch at startup and the fan runs.

The idea of the relay is to bear the high current load not the switch... You just use a switch to control the relay (temperature switch, manual switch, etc)
 

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Dan,
Technically not true - the water temp differential will circulate the water through the engine. On the practical side - I wouldn't bother leaving it running either.
 

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Gil
On a 0 332 209 150 BOSCH relay use terminal #30 as 12v B+ it is N/C on #87a . #87 is energized when power is applied to #85 and #86 closing the contact making the voltage flow through #30 to #87 and out.You use a switch to power the relay that will be carring a large current load. Horn, Fan, Lights, FuelPump,etc..
LUCAS SWITCHES
The three position Lucas switch - Dim, Flicker and Off.
Or what about the other 3 settings: Smoke, Smolder and Burn?
 
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