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Old 05-04-2006, 05:35 PM
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#1 Cooling Fan Not Working Properly??

Hello Folks,

My #1 cooling fan will only come on with A/C activated, I would like to just add a switch in place of the relay, which will mean removing relay and putting in a wire from Hot side (60 AMPS) to a switch inside under dash.

Is this do--able, looking in the Haynes manual, the control side of the relay are both Hot(ECM Battery fuse 20A)Hot at all times, the other part of the relay has a MAXI fuse 60 AMP Hot at all times.

What way can I setup this with a manual switch? I can't find a 60 AMP switch anywhere.

I hope this is clear (understandable)?

Any help is appreicated!! Thanks,
willy1

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Old 05-04-2006, 07:11 PM
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Doc here,

For a Manual override , you need to track down the wire from the RELAY coil (usually a ground side) to the Temp sensor, And / or other switch..In the case of the A/C activation on, it may be the hot side of the Relay coil..

You'll have to look at your diagram to see what turns the relay on in A/C mode to be sure, find that wire, and if it is a ground activation, run it to a switch that has the centerwiper grounded. Reverse is true if it's activated by 12 volts..In this configuration, It will manually turn the relay on and off bypassing the switch / sensor..

You can't just pull the relay and bypass the contacts with a switch..the "60 Amps" Say's it all..(assuming 30 per fan..) Most aftermarket switch contacts are only good to about 5 amps..You'll burn the switch up and possibly start a fire. Unless you can find one rated at 60 amps contact rating, you'd probably need a trailer to pull it..(exaggeration..But it would be big and bulky..)

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Old 05-04-2006, 07:17 PM
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Sounds like the fan and the relay are working OK when the A/C is on.

If you want to run the fan manually, just add a switch that will energize the relay coil.

Typically this is done by switching the ground side of the relay coil.

The relay coil has an ignition ON hot feed.
When a switch makes a connection to ground, the coil will activate the relay and run the fan.

This is a common arrangement with engine temperature sensors that control the ground side of the relay.

The manual switch is another path to ground to activate the relay.

vicrod
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Old 05-05-2006, 11:21 AM
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Thanks Guys,

I believe I understand,... In the manual all inputs to the coil side are coming from the PCM(Power Train Control Module) if I run one or any of these wires to ground it should start that relay..Correct??

The relay to the compressor is also wired the same a wire from the PCM to the relay coil.

The wires going to the PCM: Do they need to be cut, if I tie into this wire piggyback it, will it cause a problem in the PCM or should I disconnect it and put a wire nut on it?

Thanks a Bunch!!
Willy1
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Old 05-05-2006, 03:51 PM
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Doc here,

If you Want to run it in manual and Automatic , And the wires are from a BCM, Most likely the *Ground* side is not true Ground..

Most BCM "Low" output functions are actually a high speed "Low" or negative pulse..Hard grounding MAY damage the quad driver..

To do that, get a Double pole Double throw switch, (6 contacts 3 per side/On/On),

Cut the BCM/Relay Wire, and extend to your switch.

Wire the BCM and fan relay wire to one set of terminals , Center wiper and lower terminal on the same side. This will be automatic.

The other side set of terminals will be Center wiper to ground and the upper Terminal to the relay..

In this configuration, The switch will be in automatic when in the up position and manual in the down position, but hard ground and BCM will be isolated from each other when you throw the switch.. (just to be safe..).

This way , there is no chance of damaging the BCM from a "Hard Ground".

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