This is posted in the FAQ section.

Q: Can the fans be rigged to come on while the engine is not running?

A: Yes. There is a temperature sensor on the block (passenger side under the third spark plug) with one wire going to it. Take the wire off and splice another wire off of it. Route that spliced wire into the car and up behind the dash. Then just hook it up to a switch. Run another wire from the other contact on the switch to a ground, and then when you switch it on, both fans will come on high.

My questions are how will this effect the computer? Will this mod throw a trouble code? How will the computer react to this when the ECM sends a signal to turn the other fan on (passenger side) while both fans are all ready running? Finally, does anyone make a manual fan override setup like the fourth gens have? I would prefer this setup because the fans will operate normally and if it gets too warm, just hit the switch!

 

This item in the FAQ is incorrect - I'll notify the admin....

The fan relay(s) control the fan(s). The coil of both relays receives power from the ignition switch. The coil of the primary fan relay is controlled by (grounded by) the ECM, and the coil of the secondary fan switch is controlled by (grounded by) the temperature switch in the passenger side head, or the A/C liquid line high pressure switch. Grounding either of the coils will run the fans when the ignition is switched on, and will not effect the computer. If you want the fans to run with the ignition off, you must power the relay coils, as well, and diodes must be used on the factory ignition feeds to the relay coils to block the current from flowing back into the other devices connected to the ignition circuit.

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Tim

1992 Z28, 305 TPI 5 speed, 12.1 sec @ 114.7 mph

1984 Berlinetta 305 TPI Auto, 13.8 sec @ 99.7 mph

 

Thanks for the help Tim! Will the FAQ mod work properly if the ignition is on? I just need both fans to be on high constant when ever the ignition is on. I dont mind having to use a manual switch. I'm having cooling problems since I installed the custom aluminum ram-air boxes. No air is getting to the radiator from the grill openings, all of that air is going straight into the filter housing! The cars pulls alot harder with the ram-air, but in warm weather, it now gets upto 225 - 230 withOUT the AC running!

 

All you have to do is put the ground wires in series by tying them together,then putting that wire through a switch and the other to ground.I dont run the factory ecm anymore so I run both fans off the fan switch in the head.

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Check out my Hompage,or the beginnings of one.355 dynoed at 400HP at 5800RPM & 410LBFT of TQ,on Motorhttp://www.procharged89z.cz28.com/index.html

 

You mean connect both negative relay coil wires together in parallel......Actually, you can do that, but the problem with that, if you retain the computer, is that the computer looses the ability to run just one fan, which puts more wear on the second fan & takes more power, which can be a concern if underdrive pullies are used.

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Tim

1992 Z28, 305 TPI 5 speed, 12.1 sec @ 114.7 mph

1984 Berlinetta 305 TPI Auto, 13.8 sec @ 99.7 mph

 

I've discovered on my car as well (by having both fans turn on together) that the factory wiring cannot handle (at least on my car) both fans running at the same time. The 20a fuse blows in a split second of them both comming on. But that's the least of my problems at the moment.

I don't know if this is true for all 3rd gens w/the dual fan setup, but if it is, it could be a problem if ever the 2nd fan comes on at the "emergency temp" it's designed to.

Then again,, since I have the knack for finding the only defective products, it could just be a problem on my car only.

Tim, since you seem to know a bit about this subject. Doesn't the ECM watch the coolant sensor in the intake base to turn the fan on at the 235 temp ? If the JET coolant sensor replaces the original on the pass side head (at least I assume from the look of it's design), would that make the aux fan kick on 1st (at 200 I think it is)then the ECM controlled at 235 ?
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[This message has been edited by deadbird (edited July 16, 2001).]

 

Oops,that is what I meant
I have to run it this way becaue my Tec 2 only has one output for either a fan turn on or tcc control and I have it wired up for tcc control.I have to tell most here when I did this mod the car wasnt a stocker,I had a blower on it and this helped cool it down quick and keep the temp stable in hot weather.I wouldnt recommed it for close to stock vehicles.Use this mod wisely i guess



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Check out my Hompage,or the beginnings of one.355 dynoed at 400HP at 5800RPM & 410LBFT of TQ,on Motorhttp://www.procharged89z.cz28.com/index.html

 

The two fans are controlled independently. If you "tie them together", both fans will come on when either "controller" requests fan. First "on" request gets both fans. Last "off" request shuts them off.

Mine are protected through a fusible link. I've had mine tied together for over a year, now, and haven't blown anything (except air across the radiator ), yet. I had mine wired to come on with the ignition off, as well (only the pass head switch is effective then), but it took too much of a toll on my battery. Both fans would run for as much as 20 minutes after shut down (using a 225* switch). Now that I'm burning PROMs, I can control the fans there. It makes the pass head switch pretty useless, in my case.

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'87 IROC 5.7l TPI - original owner!

 

my brother did his own riggin'- he took the wires off the relay and ran them to the blower motor and spliced them into the relay on the blower motor. now he's got the fans rigged up to be controlled my the fan switch! its adjustable fan speeds accessible through the inside of the car. its kinda lame, but it solved the problem of the fans not coming on at all

 

So if I splice a wire into my primary coolant fan relay, and my secondary coolant fan relay, and run them to the same switch, which will ground both of them, this means that when i don't have the toggle switch on and the ecm turns the primary fan on, the secondary fan will go on too?

Does that make sense, or did I misread something in the post?

 

all that the sensor in the passanger side of the head does is ground the system. so if you want to retane the factory settings but still have a switch. all you have to do is run a wire from the sensor wire (keeping the sensor connected) to a switch in the car someware then to a ground. This will run both fans on high. But only if the car is on. with the switch off it will act like normal. also the ecm will not no a differnce

 

sorry my above post will only operate the secondary fan

 

If you read carefully and do a little homework, you'll discover that that isn't the only FAQ, Tech Article, or Tech Data that is either blatantly incorrect , misleading, or presumptive.

The sad part is, I doubt that anyone has the spare time to clean it all up. Hey - Dave Mustain hasn't been doing much lately...