Activate idle up with electric fan?

[daktah]

Anyone know if it's possible to make an electric radiator fan trigger the idle up solenoid while it's on similar to the blower and defroster? It drags my idle down by about 200 rpm and brings my alternator voltage down from the load and lower rpm.

[evildky]

Possible sure, I have no idea how to do it but I'm sure it's possible.

You just need to determine what signal the the ecu needs on what pin to activate high idle or figure out what signal on what wire the ecu sends to the ficv to turn it on. I'd think it would be simpler and safer to trigger the ficv. Most likely 12v or switched ground.

[centralcoaster33]

It's my understanding that those systems trigger the use of the auxiliary air control valve (AACV). Which is like and in addition to the IACV. So, have you done an AC delete? If so, just pair up the AC switch to the fan switch and if your car thinks the AC is on, it will use the AACV during idle I'm pretty sure. If you don't have a delete, you'll want to duplicate the signal for the idle up without engaging the AC system, so at that point I'd look to the wiring diagram and written explanation of the AC system and see about tapping into the part that triggers the AACV. So a little FSM studying would be your next step.

Additionally, you could look into why your car can't handle the draw of an electric fan. That seems like an issue in itself worth investigating.

[daktah]

I'd think it would be simpler and safer to trigger the ficv. Most likely 12v or switched ground.

Duh Why didn't I think of that. If it's just a plain old 2 pin solenoid I'll just splice it into the fan relay wiring and it should get 12 volts whenever the fan turns on

It's my understanding that those systems trigger the use of the auxiliary air control valve (AACV). Which is like and in addition to the IACV. So, have you done an AC delete? If so, just pair up the AC switch to the fan switch and if your car thinks the AC is on, it will use the AACV during idle I'm pretty sure. If you don't have a delete, you'll want to duplicate the signal for the idle up without engaging the AC system, so at that point I'd look to the wiring diagram and written explanation of the AC system and see about tapping into the part that triggers the AACV. So a little FSM studying would be your next step.

Additionally, you could look into why your car can't handle the draw of an electric fan. That seems like an issue in itself worth investigating.

The car has its AC system removed it's going to get reinstalled in the near future so I don't want to mess with any of the AC wiring. I also really don't feel like taking the time trying to replicate a signal in an ancient ECU so I'm just going to go with the splice into the iacv method.
It's pretty simple why the alternator gets saturated at idle on the fan kicks on. it's a 70 amp alternator so it can put out 70 amps at 3k or 4k (or whatever the manufacturer produces it for), at idle it's going to be more like 35. That 35 amps needs to drive the entire vehicle Electric System (aside from HVAC and defrost Because they kick on the iacv) including ignition, injection, timing, the ECU, radio and amp, and all the various sensors and lights and indicators and other doodads. The bare minimum this is going to draw is like 15 amps, leaving ,20 amps of overhead at idle. Now add in a big electric fan that draws 20-25 amps while running and over 40 at startup and it's easy to see how it immediately saturates the alternator which loads the engine and drops the idle, which drops the voltage, making the fan and whole system use more current to make up for the voltage drop.
I'm planning on installing a cheap gm 110 amp 3 wire later on to solve this problem at the source.

[centralcoaster33]

Since you have AC delete, you don't even have to pair up or rewire anything I think. Simply push the AC button and leave it on. That should trigger the AACV when you idle... at least it did on my car in the past. I didn't have such low power, but I did have low idle and that helped form me then. I guess for your car it might make the idle too high if it were on and the fan wasn't, but I'd try it to see... can't hurt and could save you some rewiring time.

As far as the IACV, I thought those received a variable voltage signal, so that they open part way and all the way and such, as needed. I could be wrong about that.

[daktah]

I'm pretty sure it's not variable Because whenever I hit the HVAC or defrost it always idles up to the exact same rpm, 900 to 1200 where I set it. I jumped it with a 5 amp 12v battery as well and it went straight to 1200 too so splicing in the rad fan relay should work as intended.

[centralcoaster33]

This is good to know. Thank you.