kicker kx850.2 overheat

[Dannie717]

This Kicker kx850.2 played at a high level for an hour. The heat sink measured 110 deg.F. but the fan will not come on. I tested the fan on a 12 v power supply and it checks ok. B+ is measured from ground to the fan socket + terminal, but 0v across both terminals.
Any ideas anyone?

[Osvaldo de Banfield]

May be that the fan is driven by a transistor or fet at a given temperature. The, some components in the sensor may be fake, for instance, a PTC, a NTC, or other thing. Also a transistor may be open circuit. Finally, may be a op amp or comparator used with a reference voltage, some of them also may be faulty.

[Osvaldo de Banfield]

Also the temp sensor can be a diode like an 1N4148.

[Perry Babin]

110°F is very cool for electronic components. Don't expect the fan to come on until the amp gets too hot to hold your hand on it. The fan runs at 2 speeds. It won't run at high speed until the amp is so hot that you can't hold your hand on the sink for more than a second.

Generally, the fan will spin up for a second when the amp is initially powered up. If it spins, everything is probably OK.

[Dannie717]

Thanks Osvaldo for the suggestion.Perry, I heated the heatsink up to about 150 deg.F. and that fan kicked right in! Thanks again Perry.