fan relay diode
Thread Starter
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
fan relay diode
recently there was a post that referenced a fan relay diode that would ground any current developed by the fan suddenly free-wheeling while the car was at speed and the relay opening. made sense to me so i got a tyco relay (same specs as the bosch relay mentioned in the post). i was surprised to see the schematic showing the diodes on the coil, not the contacts!
can anyone explain this to me?
can anyone explain this to me?
Le Mans Master
Joined: Apr 2001
Posts: 5,000
Likes: 1
From: Minneapolis, Mn USA
Some of the Bosch HD relays have suppression diodes across the contacts built in. I know the 70A units I installed do.
Then you should also install another diode across the fan motor + to -. This is called the Freewheeling diode and suppresses the voltage developed by the fan motor as it freely spins after 12V power is removed from the motor windings.
The relay contact will remove the fan from the 12V circuit, but the voltage needs a path to dissipate through and this is what the freewheeling diode provides. A 400V 3A (1N5404) or 1000V 3A (1N5406) diode is a good unit. You can get them at Radio Shack.
Schematics on how to do this are all over the web. Look up Mark VIII wiring or Electric fan wiring to find them.
B...
Then you should also install another diode across the fan motor + to -. This is called the Freewheeling diode and suppresses the voltage developed by the fan motor as it freely spins after 12V power is removed from the motor windings.
The relay contact will remove the fan from the 12V circuit, but the voltage needs a path to dissipate through and this is what the freewheeling diode provides. A 400V 3A (1N5404) or 1000V 3A (1N5406) diode is a good unit. You can get them at Radio Shack.
Schematics on how to do this are all over the web. Look up Mark VIII wiring or Electric fan wiring to find them.
B...
Safety Car
Joined: Oct 2007
Posts: 3,729
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From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
Diodes across coils...
almost all newer electronic systems incoroprate Diodes across all coils, (relays, Solenoids) this surpresses EMI backfeeding into the system and reduces high voltage spikes which can kill electronic omponets.
69VETT
69VETT
