Cascade Crew

Xophertony · Posted: Thu Sep 28, 2006 12:48 pm Post subject: dual fan woes

so i found out why my second fan is not enough to keep my GTA cool in traffic. ::drumroll:: the first fan does not work. i was at 225* (ish, stock guage so anyones guess realy) and the fan was not on. time to do some investigation. does anyone know exactly where on the block the primary fan temperature sending unit is?

aaron_sK · Posted: Thu Sep 28, 2006 1:07 pm Post subject:

I may be very wrong, but I belive that the L98 fan runs from the same sensor as the ECU, which is a different sensor from the guage. If so, it'd be the one under the TB on the front of the intake manifold.

*Edit: Have you checked the fan? Maybe the motor is burnt. It does happen.

Dewey316 · Posted: Thu Sep 28, 2006 1:11 pm Post subject:

I think it uses both.

One is activated by the fan switch on the passanger side head, the other is activated by the ECU.

Maybe someone with TPI will actualy know though.

Xophertony · Posted: Thu Sep 28, 2006 1:19 pm Post subject:

well, i found the relay, and grounded it (as if i had flipped a switch, or the sensor had tripped) and it came whirring to life. the fan is good, and the relay is good. the fault is somwhere in the path to ground from the E terminal. the switch terminal. this does however give me a way of driving around with the fan working, i just need to ground the realy so the fan will be on when the car is on. but i would realy like to get it working right.

there is an article on TGO explaining the dual fan system. think i will do some reading.

EDIT* or TGO is down.... So mad I can't see straight

Xophertony · Posted: Thu Sep 28, 2006 1:45 pm Post subject:

ahhh... turns out, in my infanite wisdome i saved the article to my HD...

so on a TPI car the 1st fan is controlled entirly by the ECM and does not come on until 222*. the article did not actualy say where the sensor is. so for now i am jst going to connect it to the ground for my second fan, this way when i flip the switch BOTH will come on. i'll figure out why it is not coming on when it is suposed too later.

Twilightoptics · Posted: Thu Sep 28, 2006 9:36 pm Post subject:

Alright Tony... one your cylinder heads... there is a switch on EACH SIDE. ON the drivers side its between 1 and 3 just below the header. On the passenger side it's between 6-8 just below the header. They look the same.

One is the secondary fan on. The 2nd is the sending unit for the gauge.

Unplug one... if your gauge reads proper temp... IE unplug when engine is warmed up... then you''ll know.

There are 2 relays... one for each fan. You can actually piggy back the relays to either run off the block switch (you can get 180deg 160 deg etc), a single wire grounding switch, or to both run off the ECM.

You don't want to run both off the ECM and let the ECM ground both... or you could fry the ecm. Too much power. It's designed to only ground one relay at the terminal.

Mike an I have both ours setup to piggy back. The one relay connected to the ECM, you run the other relays so that the ground on the 2nd relay is connected to the large out of relay #1. So when #1 comes on and allows power to go to the fan... the 2nd relay comes on... might need to play around with it... I THINK that's how ours are wired but I can't remember exactly. Either way when you turn the car off... the first fan turns off but acts as a generator for about 10 seconds and the 2nd fan stays on until the first fan stops spinning. Kind of like a ghetto intercooler engine on thing lol.

I also have a single wire coming off the ground side of the first relay into my console as a "just in case" type of deal. Have it hooked to a switch, then grounded to the body. Flip the switch and the fans come on at any temp.

<<<< had lots of fan troubles on my '85.

Xophertony · Posted: Thu Sep 28, 2006 11:50 pm Post subject:

ok i am swimming. i think i can figure all this out.

question: does your ECM have anything to do with your fans on your car?

idealy i would like it to work like this:
fan one: ECM actuated at my own custom temp.
fan two: block sensor/switch oporated. i would probably get a block sensor that turned it on at 180*-200*

or if that is not possable just "piggyback them off of the block sensor/switch (like they are now) with a 180*-200* block sensor

Twilightoptics · Posted: Fri Sep 29, 2006 6:29 pm Post subject:

Schultzy89GTA · Posted: Fri Sep 29, 2006 9:03 pm Post subject:

aaron_sK · Posted: Fri Sep 29, 2006 9:18 pm Post subject:

Xophertony · Posted: Sat Sep 30, 2006 12:35 am Post subject:

i know how it works stock. i am saying idealy i would NOT like to piggyback them both off the block switch.

on my car it is the driver side one that is for the guage. is that the one for the ECM also?

chevymad · Posted: Sat Sep 30, 2006 11:02 am Post subject:

The ECM one should be up by the thermostat. Passenger side is the fan control and drivers side is guage. For a lower temp fan control switch, I used a marine application idiot light sender. Comes on at 200*. It doesnt have the correct plug_in however. It has just a 1/4" blade terminal. Which was fine for me cause the original connector melted around the headers anyway.

Xophertony · Posted: Sat Sep 30, 2006 12:22 pm Post subject:

aaron_sK · Posted: Sat Sep 30, 2006 1:43 pm Post subject:

Twilightoptics · Posted: Sat Sep 30, 2006 3:47 pm Post subject:

There is nothing wrong with piggy backing.

Off the ECM or block switch.

I think the ECM is better at controlling the fans than the block switch... so I did away with it. Also freed up spark plug access on the passenger side and a wire.

No part number. I never could find that switch in the napa books, but never looked in the marine applications.

chevymad · Posted: Sat Sep 30, 2006 7:00 pm Post subject:

Sorry, no part #. I just replaced it to. I think i melted down my old one on the canadian trip due to ecm/timing issues. I know I only found 2 marine sending units in the catalog. Only difference between the 2 was the size of the pipe thread. I think one was 3/8's the other was 1/2". They were the only 2 sending units I could find that grounded at that low of a temperature. The size you need will depend on your heads, as I don't have stock heads i'm not sure what thread you'll have. I bought hte 3/8s unit and ended up having to bush it to 1/2" myself. LOL

Xophertony · Posted: Sun Oct 01, 2006 12:16 am Post subject:

so you can piggy back them off the ECM and that is ok?

Twilightoptics · Posted: Sun Oct 01, 2006 11:26 am Post subject:

alloy · Posted: Sun Oct 01, 2006 11:36 am Post subject:

I could sure use that part number Brandon if you have a chance to look it up. I fried mine a long time ago, and as I recall the swicth you recomemded was a lot less $$$ that the ones from Summit and others.

KH29ROCKS3 · Member Joined: 27 Mar 2004 Posts: 48

Tony....

When I first got the GTA, I had to replace the primary coolant fan switch. It was bought from carquest....which would explain why it crapped out. It's located on the right side of the block, it's a single wire sensor similar looking to a knock sensor and a PITA to get too, maybe easier since it has headers now......dunno. When you remove it, you will be bathed in coolant up to your armpit so be sure it's cool.....I speak from experience. It would not turn on the fan till around 228....you can buy sensors that will turn it on at 180, 190 etc.... Get a Year One catalog for F bodies, I got one free on line...they sell them. Plug and play and no having to dick around with chip burning or wiring. Just my 2 cents....