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  #1  
Old 03-03-2009, 04:00 PM
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what causes relays to burn out

I am asking because I put some electric fans on my truck(universal type) and the relay has gone out about 3 times this year, I have a tempurature control thing on the fans and I am thinking about just deleting it and having the fans run all the time even though I think that they are doing that right now.
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  #2  
Old 03-03-2009, 04:54 PM
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High current or high temp can destroy relays. Fans draw a lot of current so you must be sure all of your connections are solid and correctly made.
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  #3  
Old 03-03-2009, 05:13 PM
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Depends on why you are replacing them.

1. If the relay is too small ( say a 20 AMP or 30 AMP relay ) for the application ( 40 AMP continual draw ) the contacts are going to give up really quick.

2. If the relay is not rated for the contact cycles you are using it for. Say you have a relay that is good for 10,000 cycles, and your fans are turning on and off enough to pass that mark in a short amount of time, then you need a relay that has a higher cycle duty rate on it.

You would need to bench test, and more then likely take the cover off the relay, and physically inspect it, to see what is going wrong with it ( blacked / melted contacts or the contacts don't move when the coil is energized ) to know what is up with it.
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  #4  
Old 03-03-2009, 06:59 PM
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I took the relay apart and saw that it was blackened so I sprayed some electrical cleaner on it and plugged it in with the ignition on and nothing happened however, I can push the contact to touch the other contact and it will turn on, and I did the whole plug a wire across to make a connection and the fans worked, but as for the amps or the contact cycles of the relay I have no idea I think it might be a 30 amp, but also it has a 25 amp fuse and it has not blown yet, slighty melted but not blown
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  #5  
Old 03-03-2009, 07:55 PM
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Sounds like the install is under sized for what you are doing.

Fuse holders and fuses should not melt at all. Sounds like the setup is running right at 24 or 25 AMPS, and some heat caused either by current inrush or under sized wire is working against you.

What size wire are you running ?

The circuit should be sized so it is 80% of the max load.

If the fans draw 30 Amps, that is 80% of what the circuit needs to be sized for, so a 37.5 Amp setup is the minimum. This means you should have a 40 Amp relay, and a 40 Amp fuse.

Also wire size plays into this, so if the above is true, that would mean 8 AWG automotive wire ( 105* C temp, not the 90* C THHN at home depot ).

If the fans are 25 AMP, you should still stick with the 40 ( or higher ) relay, that has a higher cycle count on it ( data sheet will show this value ), and run 10AWG wire both ground and power to make sure you are not choking it.

Also, only good solder splices, no butt crimps on this install ( those add resistance to the circuit ).

Sounds like it is time to start over with the install.
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  #6  
Old 03-03-2009, 09:47 PM
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yep I am going to have to start over, I am also probably, just to make it simpler, delete the whole deal that makes the fan turn on at a certain temperature and just have it turn on when the truck turns on or when I turn the AC on

and the wires running to the fans are about an 8 gauge

forgot, also does anyone know where I can get a relay block for about 4 relays, and at around 40 amps, so that way I can have just one relay per fan

also is there a way to check for how many amps the fan draws with a digital multimeter
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Last edited by Stephen87; 03-03-2009 at 11:46 PM. Reason: forgot info
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  #7  
Old 03-04-2009, 10:26 AM
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Rather then running the fans all the time, why not look at a Flex-a-lite controller ?

This has the temp probe input ( for the on / off setting ) as well as the relay functions ( solid state ).

This is Flex-a-lite part number FLX-31165
So you get an idea prior to ordering, here are the instructions
right click save as:
http://www.flex-a-lite.com/auto/31165-99943.pdf

Summit racing has them, and Amazon sells them with free shipping.

For the draw on the fan, if you meter goes high enough, switch the probe to current position, put meter to the current setting, and place inline with the fan or just check the data sheet for the fan.
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  #8  
Old 03-05-2009, 12:43 AM
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would the one that you have posted be a much better choice that what I have currently setup

http://store.summitracing.com/partde...5&autoview=sku
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Last edited by Stephen87; 03-05-2009 at 12:50 AM.
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  #9  
Old 03-05-2009, 08:25 AM
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If you are burning up relays, I would say yes.

I don't know much about the Hayden controllers myself, never used them.
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  #10  
Old 03-05-2009, 12:22 PM
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I was reading into the flex a lite and it looks to be a pretty sound controller I am probably going to go with that for the radiator fans and then I am going to rig a system to the ac compressor for the condensor fans so that way when i turn the ac on the other 2 fans turn on
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Old 03-05-2009, 12:22 PM


 
 
 
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