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View Full Version : Electrical Hum + Buzz In Engine Bay


Tillsy
07-01-2012, 10:05 AM
When in either accessory or run modes there is a hum in the engine bay. I can't seem to track down where this is coming from - anyone know what it might be, and why it would occur in accessory mode (sounds like something is draining power at a time it does not need to).

When I short the otterstat to test the fans I find that 70ish% of the time a buzzing sound comes from somewhere in the engine bay as well - sounds very much like a relay going spastic (or that silly door buzzer). Sometimes does not occur though. Furthermore the two times I have started her so far I could hear it too (though barely because obviously the engine drowns it out). Any thoughts on what this one might be?
jawn101
07-01-2012, 10:14 AM
The hum is the Idle speed motor, and it's normal. :)

Not sure about your second noise though. Maybe a video would help.
Bitsyncmaster
07-01-2012, 10:54 AM
The hum is the Idle speed motor, and it's normal. :)

Not sure about your second noise though. Maybe a video would help.

+1

My new idle ECU stops that noise (battery drain) by shutting off the idle motor power if the engine is not running.
Tillsy
07-01-2012, 06:01 PM
+1

My new idle ECU stops that noise (battery drain) by shutting off the idle motor power if the engine is not running.

Looks like I'll have to make another order with you soon then :) I can live with the hum if it's for a reason, but my bigger concern was battery drain.
jawn101
07-01-2012, 06:03 PM
Looks like I'll have to make another order with you soon then :) I can live with the hum if it's for a reason, but my bigger concern was battery drain.

Not to take away from Dave at all, since his products are awesome. But the idle motor only spins if the car is 'on' - if you're leaving it on for extended periods of time anyway (shows or something?) you could just unplug the ISM :)
Bitsyncmaster
07-01-2012, 06:08 PM
Not to take away from Dave at all, since his products are awesome. But the idle motor only spins if the car is 'on' - if you're leaving it on for extended periods of time anyway (shows or something?) you could just unplug the ISM :)

You also want to unplug the white wire off the resistor block. With the switch to on, that coil is drawing many amps.
jawn101
07-01-2012, 06:10 PM
You also want to unplug the white wire off the resistor block. With the switch to on, that thing is drawing many amps.

Ah, so it's more complicated than just killing the motor itself then. Plus your ECU provides a whole host of other tuning opportunities that you don't get otherwise. In a world with limitless cash that's the way to go for sure :)