3.4l V6 Electric fan not kicking on?
#11
12-14-2011 | 05:00 PM
Your ECM doesn't kick in the main fan til 220 degrees fahrenheit. Thats normally 3/4 of the way to red. The only way to change that is to get another Coolant sensor on a different scale but is still close.
BTW your main fan is turned on by the ECM grounding the FAN RELAY. The ground(-) from the ECM(Green wire) tells the RELAY to turn on the fan. Then it sends power if the key is ON. the relay is energized when the key is ON but needs the ground to switch the relay.
The green wire from the ECM travels right past the battery so you can just pull it out and ground it there to always have the fan on when you have the Key to ON. Better yet you can splice into it and send a wire to the dashboard with a switch. On the other pole of that switch just attach it to ground with a screw. Then when you switch it to ON the relay will get a ground and turn on the fan and you won't have to deal with any volts so it can be a cheap switch.
BTW your main fan is turned on by the ECM grounding the FAN RELAY. The ground(-) from the ECM(Green wire) tells the RELAY to turn on the fan. Then it sends power if the key is ON. the relay is energized when the key is ON but needs the ground to switch the relay.
The green wire from the ECM travels right past the battery so you can just pull it out and ground it there to always have the fan on when you have the Key to ON. Better yet you can splice into it and send a wire to the dashboard with a switch. On the other pole of that switch just attach it to ground with a screw. Then when you switch it to ON the relay will get a ground and turn on the fan and you won't have to deal with any volts so it can be a cheap switch.
The PCM does ground the engine cooling fan relay coil and that relay is in the underhood fuse/relay box.
The PCM also gets info from the a/c pressure sensor so that can also activate the fan. A dead a/c system or disconnected a/c pressure sensor makes no difference. If coolant temp reaches about 230 the fan will turn on (so long as the ECT sensor is good).
I hate this high temp on my recently rebuilt 94 3.4L. The owner's manual calls for a 180F thermostat and I'm about to install one. I'm tired of my coolant temp reaching 3/4 scale before the fan comes on. Hopefully the lower tstat opening temp will increase coolant flow enough to keep the engine temp a bit more stable. The wild coolant temp swings seem brutal on head gaskets, etc.
Last edited by 1augapfel; 12-17-2011 at 07:49 AM. Reason: correct some major memory errors on my part. oops.
#13
12-16-2011 | 02:09 PM
Newbie
Joined: Dec 2011
Posts: 2
From: Tennessee
OK i'll give away my secret
Your coolant temp sensor is just a thermistor, it varies resistance depending on temp. Its never fully open or closed.
So here is your solution:
Either program computer to turn on fan at lower temp or
Get 2 quick connect splices and a resistor. I use a 680ohm 1/2watt resistor and spliced it into the 2 wires going to my CTS. This makes it so my fan comes on a little after half way but when it is very cold in winter my car will idle a little rough for less than a minute. Also you might save a little gas with a shorter cold start cycle.
If you want the fan on at half way on the temp gauge you will need a 470ohm resistor, but you will have rough starts. Your car might die a couple times idling in the cold until it warms up. 330ohm would put you well below half way but i haven't tested that low.
Make sure you have a good spark, use copper plugs. they don't last as long but give the best spark, or iridium plugs last longer
Many gauges cover more degrees so it only seems like your car is getting too hot. It is better to run cooler for HP.
So here is your solution:
Either program computer to turn on fan at lower temp or
Get 2 quick connect splices and a resistor. I use a 680ohm 1/2watt resistor and spliced it into the 2 wires going to my CTS. This makes it so my fan comes on a little after half way but when it is very cold in winter my car will idle a little rough for less than a minute. Also you might save a little gas with a shorter cold start cycle.
If you want the fan on at half way on the temp gauge you will need a 470ohm resistor, but you will have rough starts. Your car might die a couple times idling in the cold until it warms up. 330ohm would put you well below half way but i haven't tested that low.
Make sure you have a good spark, use copper plugs. they don't last as long but give the best spark, or iridium plugs last longer
Many gauges cover more degrees so it only seems like your car is getting too hot. It is better to run cooler for HP.
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