As to jumping out the intercooler pump with a switch. Why do I have to go to all the troulbe to go to the wiring harness which is under the battery and a real pain in the butt. The wires to the pump are easily accessable. If the negative supplies the power, why can't I just put a sigle pole double throw togle switch(left-relay, center-pump, right-ground) that will switch the pump from relay to ground but will not allow feed back to the relay? This would be easy to attach.
noelvm

 

You're right that the PCM does pull to ground to activate the relay to turn the motor on. But the motor itself is on the "other side of the relay" from power. That is the relay is turned on by supplying ground, but the relay sends power to the motor, which is already connected to ground.

The easiest thing would probably be to tap into the White wire on the motor. Run that new wire to a switch and from the switch to fused power. Another way would be to wire the switch to the orange/yellow and white wires on the relay. That way you wouldn't need another fuse dangling around, but that probably requires some effort to get to the wires under the fuse/relay box.

Wires:

Motor:
Black = Ground
White = To Relay

PCM:
White/Orange, pin 70 = to relay coil

IC Relay:
Red/Yellow = Fuse #23, hot in run/start
Orange/Yellow = Fuse #106, hot at all times
White/Orange = to PCM
White = to motor


Mark
'00 Lightning
'79+ Corvette

 

Where is the infamous relay anyway? Is it any easier to get to than the wire coming out of the harness. According to Sal you can tap into the white wire with orange tracer and run to a switch and ground the other switch wire. Is this white/orange wire any easier to get to at the relay rather than the wire bundle coming out of the firewall?
noelvm

 

If you need a picture of the wiring diagram let me know and I will try to scan it and send it to you.

Mike

 

Thanks Mike, but I don't need a wiring diagram, what I need to know is the physical location of the relay. If I can find the relay I can find the white/orange wire perhaps easier than going to the wire bundle in the firewall. I guess I can try to back chase the wires to the pump.
noel

 

The relay is in the "battery junction box". That's the box in the engine compartment on the driver side with all the fuses and relays. The wiring diagrams conveniently list the relay numbers for all but the one you want. Start it up and pull one relay out at a time to see which one stops the coolant from flowing.

If you wanted to be extremely clever, with a switch and a relay you could control the pump from the central timing module. Then if you forgot to turn it off, it would automatically shut off after 20 minutes or so. The hood light wiring would probably be an easy source for that.

Mark
'00 Lightning
'79+ Corvette


[This message has been edited by Mark_2kL (edited 09-26-2000).]

 

Well? The white/orange wire from the PCM must run into this box then. It may be easier to pick up here rather than at the bundle at the fire wall. I will look tomorrow. Thanks,
Noel

 

Whatever you do, make very certain you do not apply power to the white/orange wire going to the PCM. I don't know what a replacement costs, and I hope to never find out.

 

Here is what I did. First off I wanted a stealth installation. I compromised by knowing that the only time I would need to pump water was when the engine was off (and my fans were on waiting in the staging lanes), so I created a simple way of bypassing the relay when I was at the track. Basically I used the engine fuse box to 'jumper' the pump control with a switch mounted in the cab. This requires removing the relay when I get to the track and replacing it when I leave. Here's some pics:

The jumper wires installed. I used the empty relay area to the left of the pump relay to plug female spade wires that then run to the cab.


Here is the switch mounted in the cab fuse box cover (a new unmolested one is only $9.



------------------
Joel.......
99.5 White Lightning,
SVT # 0056

 

Thanks Joel,
The switch mounts are really nice. Where did you get the switches?
Noel

 

Noel, I have the receipt at home, but I purchased the switches from an electrical supply house here in Phoenix. I wasn't sure what the pump (or my fans) was going to draw so I erred on the high side with a 20amp switch and the appropriate wire size. I now have my own digital camera (the photos posted above were taken in January), so if you need more detail let me know. The big trick was going through all the terminal bins at Ford looking for a female spade that clipped into the empty relay slots. With the jumpers removed no one would know I’ve done anything.

Joel.....