LiquidBlue

Just posting a little test/observation I made a while back in case it helps someone out concerning if their fans are operating correctly.

This is for a factory setup 1990 LB9 Dual Fans, automatic transmission:

fired her up, turned on the a/c (engine cold) both fans turn on.

turn off a/c, drive side fan remains on for about 1 min, then turns off

turn a/c back on, drive side fan back on, pass side off. about 1 min later, pass side turns on

ac off, temp now 110, turn back a/c on, driver side on immediately, pass side on in about 30 sec this time

ac off, temp now 120, turn back on, driver on immediately, pass side on in about 15 sec

ac off, let temp rise about 220, around 230, driver fan comes on. (seems too late to me in Austin) turn on a/c, pass fan turns on immediately

ac on, temp falls under 220, turn off a/c. pass fan off right away, drive side off in about 1 min

temp still under 220, a/c back on, both fans turn on immediately

Fast355

iTrader: (2)

Your observation sounds factory correct. You can either tap into the 2nd fan output on the 7730 and enable it in the tuning or replace the fan switch in the passenger side head to a cooler turn on. When I TPI swapped my 1983 G20, used the switch in the head in parallel with the 2nd ECM output in the 7730 I was running at the time. The switch was merely a backup measure to have some cooling if the ECM failed to activate the fans.

I had Nissan fans on mine and the way mine was setup the fans were dual speed. I ran a 180F thermostat. Fans were off without AC until 190F, low fan speed enabled. Drop to 185F they went off. Rise to 195F both fans on high speed. Drop below 190F both fans would reduce to low-speed. Turn the ac on, both fans on high speed with the ac request input. I also ecm controlled the AC clutch providing a turn-on delay to the clutch. At 50 mph the fans disabled unless the engine was over 210F. Under 45 mph the fans would turn back on if any of the above criteria was met, temps or a/c use. If the engine reached 210F the fans would turn back on at high speed even at 75-80 mph and help cool the engine down. The stock temperature switch in the passenger head was a backup to the ECM control and activated both fans on low-speed at ~220F which it actually came into play once when the CTS failed on a trip. The setup worked very well in DFW heat.

80schild

iTrader: (5)

curious why your pass side fan came on when the engine was cold. I don't believe mine comes on until the coolant reaches 215f or so (a/c on or off doesn't seem to matter). I replaced that switch with one for a TTA years ago. I think the stock one is 238f, which is ridiculously high in my opinion.

LiquidBlue

Because the A/C was on.

80schild

iTrader: (5)

If I start my engine cold, and turn on the a/c, only the driver side fan turns on. The passenger side doesn't turn on until the coolant temp gets to 215.

I may need to watch it again, but I believe that's the way it works.

Fast355

iTrader: (2)

IIRC it should also turn on with the a/c if the pressure is over 190 psi. The primary fan turns on with the a/c request signal, secondary fan comes on at 190 psi. On the 1987 that I TPI swapped, with the a/c on in hot weather, both fans were active well before the coolant hit 238F.

I also set my TPI swapped G20 up to have both fans on high speed with a/c in use. Makes a big difference in the ac cooling, especially at idle with a hot interior.

80schild

iTrader: (5)

I'll have to look at it again now that it's getting hotter. It was only about 75 degrees outside when I charged it up. I did change out my fan switch to the Four Seasons 36669, so it may be slightly off from stock.

1989karr

This seems correct, in your profile it says 87 GTA... if i recall, the fan operation changed in 1990 which is why LBs fan operates different from yours.... .

89 and down:
Normal cooling: Passenger side fan came on when car got hot... driver side fan came on at like 240? when the passenger side was insufficient to bring temps down. pass side is operated by the ECM, driver is operated by the fan switch in pass head
AC: I think only the driver side fan comes on


LB's is for a 90 dual fan, so operation would be different.

For me I have an 87 but I wired my fans to come on at the same time.. improves cooling and ac output significantly. That plus I have a LS shroud.

80schild

iTrader: (5)

Mine seems to work that way but it's reversed. Driver side is controlled by the ECM, and passenger side is controlled by the switch.

I replaced that switch years ago with one for a Grand National or TTA. It turns on at 215 I think instead of 238. Definitely an improvement without having to change any wiring.

Fast355

iTrader: (2)

On my G20, used a switch for a 1985ish 2.8L F-car. It comes on at 212F. I said 220F earlier, but looked up the switch I used and the specs show 212F. It was only for backup anyway as the ECM had both fans on before that in normal operation.

1989karr

It COUDL be the connestors are swtched on yours or even the original post i recall seeing the info from.



Id look at dual operation though. Really helps control heat and improve ac!