Can someone tell me where the wire (and what color) for the cylinder head temp sensor wire joins into a main harness? I have the diagram that shows the sensor under the intake but i need to tie into the wire for my fan controller. BTW 5.4 3v engine.

 

anyone????

 

Ok,
I have the diagram but have a question. It shows the signal return to be on circuit 359(grey/red). The problem is, it looks like there are a lot of signal returns on circuit 359. Can i tap in to this at the PCM or do i need to get it before it joins (if it joins) the other signal returns? I wouldnt think you would get a good reading if it joined other returns though. See below:

 

Hey Gobra:

I have looked at all the diagrams I have access to and can't find anything on that sensor more than what I have sent you. Sorry I couldn't help.

Good luck with it.

 

Thanks for your help, i have the diagrams i need, i just need some splainin now...

 

Hi Gobra;

Ummm - 'Lectricity 101: circuit 359 are all the returns to ground. Every point on that circuit is 0 volts. What you need is to tap into " C107" pin 1 ( right side of the CHT sensor - bottom right on your diagram.

Hope this helps.

BTW - what controller are you using, that requires this input, - does it not also have it's own sensor?

Cheers
Grog

 

That is what i was thinking but wasnt sure. I am using the spal controller. You tap into the temp sensor that is going to the processor, when the signal (temp readout) is where you want the fan to come on, you set the controller for that input.

So how is the processor getting a signal (temp) from the sensor? I would think that the feed line is 12 v and the thermister varies resistance inversely with temp. Therefore, there is a voltage drop and that is where your signal comes in. The processor has to get feedback from the sensor, im just trying to figure out how/where....

 

Hi Gobra;

Not seeeing the complete diagram, so I can't be 100%, but I think c107 pin 1 IS the input to the PCM.

I would guess that the PCM internally provides a regulated voltage source (not the +12v bus) - this is regualted and it needs to be to assure accuracy - most likely +5v, which is commonly used.

I checked my own '2000 diagram and that's how it's connected. I don't see it being very different - this isn't new technology.

Simple to check - hook up a voltmeter to this point and start the truck - you should see a change as the truck heats up - it won't be linear - the PCM handles the voltage/temp transfer function.

Hope this helps.

Cheers
Grog

 

Just thought of something, i wonder if the controller can handle the inverse relationship of the thermistor. It might make the fan come on when the voltage increases even thought that means that the temp is coming down. I need to contact spal.


Oh yeah, i havent found the coolant temp sensor (that reads out in the diagnostic mode). IS that calculated from the cylinder head temp? If not, where IS the sensor?

Thanks