I measured the voltage on the intercooler relay #208 with the key off and key on.

Key off- 12 volts supplied to the high current side of the relay only

Key on - 12 volts suppled to high and low current sides of the relay

Is the front pin on this relay connected to the pin 70 white and orange wire on the PCM that Sal has discussed?

If so, then grounding this front pin at the relay seems to be an easier method than cutting into wiring harness to get the pump to run. Comments?

 

Hello-

peice of cake...and no fussin' around with the wiring harness:

I used a fuse tap (with some "needle nose" modification) to tap the hot side. This allows use, key off.

Awesome mod, BTW. Esp. with electric fans.

-Andy

 

Andy,
What exactly did you do?

There are 4 blades on the relay

| | ___
| | ___

Front of truck here

Left most vertical line above is 12 volts always.
Next vertical line above goes to the pump.

Horizontal line above is 12 volts with key on.
Horizontal line above is PCM 70 wire??? My original question.

If you take the relay out and jump the 2 horizontal lines then the pump runs all the time.

I was thinking of a ground on the lower horizontal line above so that the pump woud run with the key on.

Is this okay? Why wouldn't everyone with electric fans not just ground this side of the relay?

Mark

 

Hi-

according to your diagram, you would run the fuse tap to the forward most horizontal line....

I guess I should have explained it this way:

from a (always on) 12 volt power source (battery or distribution block) run a wire to a 20amp in-line fuse, then to a GROUNDED switch. From the switch, run accessory power (switch on) to the fuse tap.

this hook-up requires a 3 prong switch (power in, ground, power out)

By electric fans, I meant aftermarket fans for the heat exchanger, not for the engine.

Hope this helps-

Andy

 

Like this

| | ----
| | --x-- driverside

Front side of truck

Are you saying to jump the 2 bold lines together ?

 

just a fuse tap on the one with the "x", no jumpers.

 

Nope, just more confusing to me. You are running 12 volts to the --x-- below?

+12 Pump +12 key on
| | ----
| | --x--


Front side of truck

My understanding is that if you ground the --X-- terminal above the relay will close and the pump will run. The PCM works by grounding not suppling voltage.

 

Hey guys I wired up my switch up this evening. I only linked these 2 wires and the switch turns the pump on and off. In off position the pump operates as normal.



The wires that need to be linked are where the X's.


| | -----
xx
| | -----



Front
of
Truck

Im not saying the way that is posted above is wrong, Im just saying that this has worked for me. I did a few temp tests tonoght and posted the results @ https://www.f150online.com/forums/sh...hreadid=123327

 

Buzz,
Yes that works you are just jumping the High current 12 volt supply to the pump. I am still searching for the answer if it hurts to ground the PCM output pin.

Mark

 

We used to ground out the e.fan pin on the pcm on cobras to turn the e fan on manually. Doesnt hurt a thing.

 

**** I remember that too, the only problem with grounding the pcm wire is the pump will only come on with ignition on. As far as I know on my truck the pump is on when ever the truck is running, I (we) were looking for a way to circulate the water in between runs at the track.


Mark, grounding the PCM has no ill effects, the downside it the pump only runs when ignition is on.

 

Well whats the diff whether the iginition is on or off? You are only going to be running that pump with an e fan in manual mode and will spals on the intercooler for 8-10 mins max. At least this way, the iginiton on sort of gives you a reminder to keep an eye on time.

 

The difference is power to all components will kill your battery fast, with only electric fan and pump on battery will last longer. I guess Im just lazy and dont wanna have to turn the heater,stereo and subs off, I just wanna flip a switch. Also if Pre 02 guys wanna lock the truck and roam, they can without worrying about somebody enjoying their truck. Not everybody can lock the truck, walk away and ude the keypad to reopen.

 

Your electric water pump is wired for key-on. Then you have a serious power draw.

My intercooler set-up (not better, just different) allows key off use only. when I key on, my pump switches off, and my Maziere kicks on.

Key off: Intercooler pump, elec. fans, NX-Ntercooler

key on: Water pump, Engine fan

This all driven by two dry-cell (NAPA) batteries.

I guess it's my reminder to pay attention to both cooling systems.


And the voltmeter!!!


-Andy

 

Andy, Were you addressing me or **** ? The way I did it, I can turn pump on without the key even in the ignition. This is what Ive observed on my truck, whenever the truck is running the intercooler pump is on. If I was to ground the wire at the PCM (Pin 70)with a switch, the pump can only come on with the key in the run position. This is the reason I did it the way I posted above, is this the way your method works ? In my above post I was letting **** know the reason I didnt like grounding the PCM. Lemme ask you this because your obviously more electrical savy than me, what advantages or disadvantages do you see in the way I have it done ? If your way is better by all means I will do it that way. Also, Have you ever taken readings to see what kinda decrease in temps the NX kit yields ? Im not speaking about intercooler exit air temps, I mean at idle, if you hit the NX cooler what kinda water temp changes occurred ?


Thanks

BTW Whats with the dry cell batteries ? Do they just power your fan and pumps or they part of the whole electrical system ?