Fan on walk-in cooler condenser won't shut off

[WillowTheDog]

So normally, the big fan on the top of our walk-in cooler will cycle on and off along with the condenser. But we are currently having a problem where the fan runs continuously - it never shuts off! The condenser still clicks on and off as necessary to control the walk-in temperature, but the big loud fan never stops. When the fan is incorrectly stuck in the ON condition, I can tap the big metal control box next to the fan and it will stop. So whatever is responsible for stopping the fan is sticking somehow, and when I hit it, it releases and stops the fan.

Can anyone clue me in as to which component I need to replace to solve this problem?

[The Viking]

The fan relay...

[install monkey]

contactor /relay stickin

[1mikeefc1]

Sounds like fan speed controller, relay or contactor dependant on what controls the motor.

[monkey spanners]

Fan doohickey.

[WillowTheDog]

Thanks for the help guys. It sounds like the consensus is the contactor/relay.

Here is a photo of the contents of the control box:

http://goo.gl/rnyA5

I'm assuming the faulty part is the thing at the top (labeled "C1"). Right?

Here's a close-up:

http://goo.gl/Lyt1P

Any other troubleshooting advice? Can I lubricate it or something to stop it from sticking?

[install monkey]

does c1 contactor feed the fan or compressor and fan? as there 2 lots of fuses- usually 3ph oncompressor and 2 phase for the fan

[WillowTheDog]

I think the contactor feeds both the compressor *and* the fan. The bank of three fuses on the left feed the compressor while the bank of two fuses on the right with the smaller gauge wires feeds the fan.

So if the compressor is cycling fine but the fan is not, then the contactor is probably OK and the problem is elsewhere, right?

[install monkey]

yep- if the contactor was sticking then the compressor and the fan would continue running together- as long as the cables to the 2 fuses is fed off the load side of the contactor( when not energised the power enters the top of the contactor

I think the contactor feeds both the compressor *and* the fan. The bank of three fuses on the left feed the compressor while the bank of two fuses on the right with the smaller gauge wires feeds the fan.

So if the compressor is cycling fine but the fan is not, then the contactor is probably OK and the problem is elsewhere, right?