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2G Cooling issue, plus wiring them up

spooln4fun

Proven Member
623
2
Jul 9, 2005
BELPRE, Ohio
First off my thermostat housing has all new sensors(2) car starts drives fine......the rad. fan will not kick on what so ever. I have checked my thermostat, the relays, and fuses.
Any onehave any insight on how to correct my fan from not turning on.
OR does anyone know which wire on the fan is the hot wire so i could run it to accesory so it will turn on and off with the car?
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
Since the ECU controls the fans on a 2g, your ECU may be bad (eg. leaking capacitors). As to which wire is hot, it matters much whether you have the two stock 3 speed fans (yes they are actually 3 speeds - not 2) and wiring or some aftermarket single speed fans which may have changed the wiring.

If stock:
(Note: the wire names are my own where hi/lo corresponds to the fan relay's hi/low name.)

Passenger side (radiator) fan wires on harness side of connector are:
lo positive (+12V) = white/black (white with black stripe)
lo negative (goes to ground) = black
hi positive (+12V) = white/blue
hi negative (goes to ground on M/T, switched on/off to ground by the 5th radiator fan relay LO2 on A/T) = blue/green

Driver side (A/C) fan wires on harness side of connector are:
lo positive (+12V) = blue
lo negative (goes to ground) = blue/black
hi positive (+12V) = blue/white
hi negative (goes to ground) = black

[Note: See here if wish to see wire colors on original fan side of connector (going to original fan motor): http://www.dsmtuners.com/forums/newbie-forum/261629-fans-running-all-time.html#post151198132]

Interesting note: The stock turbo 2g fans have 3 speeds (not counting off) but only 2 speeds are used (why many people call them or think they are a two speed fan). M/T uses off, medium, and high on the radiator fan. A/T uses off, low, and high on the radiator fan. Both use off, medium, and high on the A/C fan. The ECU controls the speeds based on engine water temp, vehicle speed, and whether A/C is on/off (http://www.dsmtuners.com/attachments/fan-operating-mode-2g-jpg.86862/).

The speeds are not obtained by voltage on a unique specific wire pair but rather voltage on wire combinations. Thus my wire names and their relay names are somewhat misleading. Low speed is voltage on one positive wire (either lo positive or hi positive) and ground on one negative wire (either lo negative or hi negative) although most 2g dsm's use lo positive and lo negative. Medium speed is either voltage on two positive wires and ground on one negative wire OR voltage on one positive wire and ground on two negative wires (most 2g dsm's use the latter). High speed is voltage on both positive wires and ground on both negative wires.

When people substitute a single speed after market fan they tie the positives together and the negatives together so it is always either off or on high speed (fans running all the time? - DSM Forums).
 
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spooln4fun

Proven Member
623
2
Jul 9, 2005
BELPRE, Ohio
You always come through with awesome information!
At first they didn't kick on at all, so i messed with the wires and just had a bad connection, and they kicked on....later i read, that turning the a/c on and pushing the button kicks on the other fan so i did that to have on efan all the time........now the rad fan doenst work so i used a inline fuse and jump the relay (leaving it out) and worked for awhile till the fuse blew and melted the fuse holder...(i took out the second from the left relay)...after this i thought i would try a couple more relays (one at a time) to see if would work....now when i turn on the a/c and hit the button that fan no longer kicks on, and when i bypass the seond to the left relay(which fuse box says rad fan lo) both fans kick on.....is this the ecu and shorting out due to my stupidness?
 

spooln4fun

Proven Member
623
2
Jul 9, 2005
BELPRE, Ohio
Sorry to be late, was worried about the other thread..........YES my fuse box cover looks just like that
It was the first Rad fan relay when reading left to right...
Yes stock fans

stock relay has pins as follows
___
___

| |

I put a jumper from the bottom horizontal line, to the vertical line on the left with a fuse,

worked fine for a while then just stopped that one day
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
Sorry to be late, was worried about the other thread..........YES my fuse box cover looks just like that
It was the first Rad fan relay when reading left to right...
Yes stock fans

stock relay has pins as follows
___
___

| |

I put a jumper from the bottom horizontal line, to the vertical line on the left with a fuse,

worked fine for a while then just stopped that one day
The pin numbers are confusing because the connector is viewed from the fan itself side. So viewing where the relay plugs in from above, the bottom row is actually pins 1,2,3 from left to right. So you just jumpered pin 4 (bottom horizontal) to pin 1 which is not good. That connects the radiator fan HI positive to ECU pin 20 and also to the A/C fan relay HI's coil. This is totally wrong and may even have blown out the output transistor on ECU pin 20 should radiator fan LO1 activate (heavy current would go through fan motor positives to ECU pin 20).

If you jumpered pin 4 to pin 3 (which I think you intended) that would activate the fan with the ignition switch BUT you will then have all the heavy fan current going through the ignition switch which is not intended and will blow the 30A fuse when all the other stuff on that fuse is activated. It also would probably melt some wires between the jumper and the ignition switch since they are not rated for that much current. And not to mention possibly burning out the ignition switch. Don't do this. :nono:

The proper way to bypass ECU control and just have fans run when ignition switch is on is to leave all relays in (you must use relays due to heavy fan current) and re-wire the relays pin 1 to go only to ground. Since radiator fan relay HI pin 1 already goes to A/C fan relay HI pin 1, you only need to ground it and then ground radiator fan relay LO1's pin 1 to get the hi speed. Or better yet, connect all the relay pin 1's together to go to a switch on the dash with other side of switch to ground so you have on/off control. Do not leave any of these relay's pin 1 connected to ECU pin 20 to prevent any possible ECU damage (it really shouldn't cause any damage but just to be safe).

Note: You may want to read my updated post 2 to see how fan speeds are derived.
 

spooln4fun

Proven Member
623
2
Jul 9, 2005
BELPRE, Ohio
Alright so i did something wrong for sure! What i am getting is I can either by pass the ecu and it haveing control of the fans by either grounding all pin #1, or by the other method which was dicussed here http://www.dsmtuners.com/forums/showthread.php?t=273919

When you pull the relay...and your looking at the empty socket...which is pin1? This way seems alot more simple, and cleaner looking for the engine bay

If I put a switch in to control the ground...if I leave the switch off does it put the ECU back in control?

is there anything I could check to see if I shorted out like the relays(how?) and I have checked all fuses already just have never gotten the ecu to turn on fans since i've bought the car due to not have a actual connector on the coolant temp sensor(the 2 wire one) so i had to guess which wire was what
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
Alright so i did something wrong for sure! What i am getting is I can either by pass the ecu and it haveing control of the fans by either grounding all pin #1, or by the other method which was dicussed here http://www.dsmtuners.com/forums/showthread.php?t=273919

This method is far better since you use existing relays and fan wiring and don't have to find a key ON wire.

When you pull the relay...and your looking at the empty socket...which is pin1? This way seems alot more simple, and cleaner looking for the engine bay

Pin 1 is lower left.

If I put a switch in to control the ground...if I leave the switch off does it put the ECU back in control?

It should if you leave the wire connected to ECU pin 20 and you haven't burned up it's output transistor. What size fuse did you use? Do you know if rad fan relay LO1 (the normal LO fan relay) kicked on while you had this fuse in there? If not or that relay wasn't there, you should be ok.

is there anything I could check to see if I shorted out like the relays(how?) and I have checked all fuses already just have never gotten the ecu to turn on fans since i've bought the car due to not have a actual connector on the coolant temp sensor(the 2 wire one) so i had to guess which wire was what

All the relays in the engine fusebox are the same so you can try any relay in one of the other slots, like the horn or headlights one. Without a working coolant temp sensor the ECU will never turn fans on. On it's connector the black wire is the sensor ground (goes to ECU pin 92 and other sensors grounds) and the black/white is the sensor signal (goes to ECU pin 83 only).
Got all that now?
 

spooln4fun

Proven Member
623
2
Jul 9, 2005
BELPRE, Ohio
When you pull the relay...and your looking at the empty socket...which is pin1? This way seems alot more simple, and cleaner looking for the engine bay


Quote:
Pin 1 is lower left.
GOT IT:thumb:
It should if you leave the wire connected to ECU pin 20 and you haven't burned up it's output transistor. What size fuse did you use? Do you know if rad fan relay LO1 (the normal LO fan relay) kicked on while you had this fuse in there? If not or that relay wasn't there, you should be ok.
I used a 10amp fuse, after it blew i was messing around using a direct wire
The relay was never put back in just had the wire w/inline fuse there.....I should be ok
All the relays in the engine fusebox are the same so you can try any relay in one of the other slots, like the horn or headlights one. Without a working coolant temp sensor the ECU will never turn fans on. On it's connector the black wire is the sensor ground (goes to ECU pin 92 and other sensors grounds) and the black/white is the sensor signal (goes to ECU pin 83 only).
Ok so as long as I take the black/white wire connect it to the sensor. then from the sensor i can take that wire and go straight to ground?
Should I check to make sure the black wire actually is grounded with a continuity tester or a multi meter?....IF no signal is connect I can run a ground wire over to it and connect it? or if no ground is connected car probably wouln't start


Thanks for your patience
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
I used a 10amp fuse, after it blew i was messing around using a direct wire
The relay was never put back in just had the wire w/inline fuse there.....I should be ok

The relay I was talking about is the radiator fan LO1 (3rd one in from the right). If that one was in and the ECU activated it while you had the jumper on the connector for the 5th relay in from the right, you may have damaged the output transistor. This could occur due to LO1 providing power to the radiator fan LO and some current could potentially flow out the radiator fan HI back through your jumper and into the output transistor. Anything more than couple amps would blow it. But you may have gotten lucky and it all went through the fan or LO1 never activated (most likely). Even though fan HI draws around 8A there is a much larger turn on surge which will easily blow a 10A fuse.

spooln4fun said:
Ok so as long as I take the black/white wire connect it to the sensor. then from the sensor i can take that wire and go straight to ground?
Should I check to make sure the black wire actually is grounded with a continuity tester or a multi meter?....IF no signal is connect I can run a ground wire over to it and connect it? or if no ground is connected car probably wouln't start

The sensor black/white must go only to ECU pin 83. The black wire is SENSOR GROUND which means it must go ONLY to ECU pin 92 which is connected to ground inside the ECU. Do not connect it to ground on any other metal or the ECU can get inaccurate readings (even though the grounds are connected physically, a ground loop can form causing the ECU's ground to float above chassis ground as well as noise can get injected into the ground). It's ok however to connect this sensor ground to one of these and only these sensor's ground such as the O2, TPS, Mani diff pressure, volume air flow, or fuel tank diff pressure. Notice there will be continuity on this sensor ground to engine/chassis ground anyway (since it connects inside the ECU) but the physical ground connection must be inside the ECU for above stated reason's (or engine can run poorly due to misleading sensor voltages).

The engine does not need the coolant sensor to start. It will just always run rich.

Oh BTW, you probably should not change pin 1's wiring on the A/C fan relay LO (relay on far right) as it is supposed to always be grounded so A/C fan will always go on when A/C does (regardless of anything else).

Also note that if you connect pin 1 on the other 3 fan relays together (so you can have a switch controlling them), when your switch is off the ECU will turn them all off or on together. There will be no longer be separation of fans or speeds. This is ok as long as you realize this. A more correct solution would be to use a dpdt switch with another wire from the other relay to the switch. Then when off, everything will be connected as stock. PM me for how to wire this.
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
Ok I thought about it and the switch override change is even simplier than I had thought. You don't need to change anything in the engine fusebox. Just add one DPDT (double pole double throw) center-off switch under the dash with two 20ga wires that tap into the two ECU wires as shown in the picture below. The DPDT switch is available from Home Depot ($6) and is shown in the other 2 pictures. Make sure you disconnect battery before starting and solder all connections.
2g turbo ECU pinout: 2G Turbo ECU Pinouts

Or if you always want the ECU to turn both fans on/off together, leave out the switch but tie ECU pins 20 and 21 together (and leave them still going to the ECU).

(Note: This post has been deliberately updated by me so I can link other posts to here of which DSM Wiki is one.)

(Another note: See post 26 "Actually I..." for fan speed description)
 

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spooln4fun

Proven Member
623
2
Jul 9, 2005
BELPRE, Ohio
Is a dpdt switch a basic on/off switch?

2nd. can i just connect the switch from ecu pin 20 and 21?
or
do i run a wire from pin 1 on the relay over to the a/c fan HI then to the switch?
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
Is a dpdt switch a basic on/off switch?

2nd. can i just connect the switch from ecu pin 20 and 21?
or
do i run a wire from pin 1 on the relay over to the a/c fan HI then to the switch?
1st: It is the way I'm using it (except being double pole it switches 2 circuits at the same time). You could also use a dpst but I doubt you'd ever find one.

2nd: Just connect the switch from ecu pin 20 and 21 (that way you don't have to pull the fusebox or find a way through the firewall). Leave pins 20 and 21 connected to ECU - just tap into them. You can get the dpdt switch at Home Depot or Radio Shack.
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
Nope (and that's another beauty of it). Don't forget to disconnect battery before changing any wiring (especially ECU) but write down your radio stations presets first. Let me know how it turns out.
Good Luck ;)
 

spooln4fun

Proven Member
623
2
Jul 9, 2005
BELPRE, Ohio
Will be a few days or so before i get some time to work on this here. But will let you know how it all turns out.

The dpdt switch i hook pin 20 to one, 21 to another, and the other side of the switch goes to ground so when i flip the switch they turn on...........if i leave it on it will turn on and off with the car





Just for reference purposes for people this is the link from vfaq on the ECU pinout
http://www.vfaq.com/mods/ecu-harness-2G.html
 

EagleTSIawd

Proven Member
408
8
Mar 17, 2005
Stayton, Oregon
Ok I thought about it and the switch override change is even simplier than I had thought. You don't need to change anything in the engine fusebox. Just add one DPDT (double pole double throw) center-off switch under the dash with two 20ga wires that tap into the two ECU wires as shown in the picture below. The DPDT switch is available from Home Depot ($6) and is shown in the other 2 pictures. Make sure you disconnect battery before starting and solder all connections.
2g turbo ECU pinout: 2G Turbo ECU Pinouts

(Note: This post has been deliberately updated by me so I can link other posts to here.)

Hey luv2rallye, i have some questions on the DPDT switch. Well, i dont have an ac compressor so i wont be using the a/c button anymore. I was thinking, the a/c button has 1 off position and 2 on positions, this is just like a dpdt switch right?

Is there a way to wire the a/c button to work with your diagram instead of buying a dpdt switch?

i mean, that button is going to be there doing nothing so i might as well try and put it to some good use :)

btw, a lot of your threads in here have helped me out a lot dude, you rock:rocks:
 

luv2rallye

DSM Wiseman
7,877
751
Jun 7, 2003
Minneapolis, Minnesota
I've been on vacation so I wasn't ignoring you. I haven't had it out but according to my '99 diagrams the A/C button is not a DPDT switch nor does it have a center off position. It's actually a SPST switch with 2 lights on it.
 

vr4honey

Probationary Member
1
0
Aug 25, 2006
Severn, Maryland
Since the ECU controls the fans your ECU may be bad (eg. leaking capacitors). As to which wire is hot, it matters much whether you have the two stock 3 speed fans (yes they are actually 3 speeds - not 2) and wiring or some aftermarket single speed fans which may have changed the wiring.

If stock:
(Note: the wire names are my own where hi/lo corresponds to the fan relay's hi/low name.)

Passenger side (radiator) fan wires are:
lo positive (+12V) = white/black (white with black stripe)
lo negative (goes to ground) = black
hi positive (+12V) = white/blue
hi negative (goes to ground on M/T, switched on/off to ground by the 5th radiator fan relay LO2 on A/T) = blue/green

Driver side (A/C) fan wires are:
lo positive (+12V) = blue
lo negative (goes to ground) = blue/black
hi positive (+12V) = blue/white
hi negative (goes to ground) = black
[/url]).

I have 1998 gst and my wire colors dont match yours im trying to find out whats neg and pos
 

theSicKness

Proven Member
779
4
Dec 26, 2004
Belpre, Ohio
Your wires colors should match, are you sure you are looking at the proper plug or in the proper place?
 

blakktalon

Proven Member
131
0
May 2, 2009
middletown, New_York
Ill have to try this since i have a switch laying around and i currently have my fan tapped into a switched power source so that it is on as soon as my car turns on and runs until i shut it off:notgood:
 

screaming eagle

Probationary Member
3
0
Oct 21, 2009
brunswick, Georgia
hey iv got an interesting problem. new water pump (duralast from work), good hoses, flushed and tested good rad. new felpro head gasket gettin good pressure and new thermostat plus no leaking of coolant. but the darn little 4g37 motor still overheats. i already hot wired the fans and they work great. any awnsers???????????????????????????????????????
 

Scott McIntyre

DSM Wiseman
306
38
Mar 15, 2002
Halifax, NS_Canada
Let's say I wanted the A/C fan (driver side) running all the time, to help cool off the turbo / exhaust after a hard run and to keep the A/C fan blades from melting.

Essentially, I'd like the C-F position (toggle up) to override the A/C fan alone, and override both fans when in the A-D position (toggle down). Would swapping the pin 20 & 21 wire taps (as illustrated below) accomplish this?

:hmm:

[EDIT: Crossed-out the modified diagram as it is inaccurate]
 

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