I was wondering if anyone figured a way to control both fans from the ECM with a 165 box. I did a search, and found that it can be done with the newer ECMs. I just thought maybe somebody took a different output from the ECM, and used it to control the fan turn-on. But I would want the option in the bin for fan on/off temps. That would be sweet.
Mike

 

i wired both my fans into the wiring controlled by min-mph and set min-mph for fans to turn on at 0mph... i never ever overheat and holds very steady at any desired temp.

 

I dont know what wiring you are talking about. Are you running a 165 ECM? That ecm only has outputs for 1 fan control. And I think that speed you are talking about, is just the speed that above X mph the fan WONT run. Below that speed ecm uses table of duty cycle to control fan on/off.

I might make a small wire change so that the ECM will turn on both fans at same time. I have several switches wired in, and I can turn on/off the second fan from the driver seat. I just dont want to tax the ECM with pulling current to drive both relay coils. Last year car ran cool, but this year since I had the tranny work and high stall converter put it, runs a little warmer at slow speeds. But still never above 190. Maybe I just need to flush out the cooling system.

 

yes i have the 165.

there are two fan controls.

in the computer one fan is controlled by minimum MPH (by default was 20mph i believe)

where as the other fan is controlled by engine temperature as well as other factors such as ac on/off and maybe other factors.

and the ECM is used to ground the fans IE. complete the circuit so they start. Its a poor idea to run voltage though the ecm as a voltage spike would fry the ecm. GM isn't that stupid, i hope.

high stalls also generate extra heat.

 

What bin and editor are you using? Using TunerproRT, i only see constants for Fan 1 control. I see 20mph to turn on Fan1 if AC is on. And I see 35mph to use Fan1 duty cycle table. The only way the ECM will turn on the second fan is if the fan pressure switch closes at 233psi. The other way fan 2 turns on is by the HD coolant fan switch, which closes at 238degF. That switch has nothing to do with the ECM.
Am I missing something here?

 

I'm not sure where you're getting that information, but I'd be interested to hear more. '165 ECMs have one output for fan control, and it's controlled directly by temp. The other of the two fans behind the radiator is controlled directly by a switch in the cylinder head and is "hard-coded" by the temp that the switch is designed to operate at. Further, I believe the second (non-ECM controlled) fan only comes on w/ the A/C.

-M

 

i am just stating exactly what i did. both my fans run and my temps are as steady as a car from the factory. (@185deg F)

as for which bin/definition i use. its highly modified. but i switched from the $32b to $6E and use the definition that came with tunerpro RT

 

I believe you Jay, you are prolly running both fans at the same time to keep your engine cool. I want to be able to control both fans thru the ECM with seperate on/off temps. IE Fan 1 on at X and off at Y. Fan 2 on at X+5 and off at Y. Get my drift?

Hey Mangus those constants in the $6E tdf, one is "Min MPH for using Fan 1 Duty Cycle table" and the other is "MPH for Fan1 turn on if A/C on", are those constants supposed to be speeds that the fan WILL NOT run when you are above those speeds? Some of the other constants are fairly obvious, but these ones.....

 

the min MPH constant means the fans will not turn on unless you reach that speed. which i found out was why my car would overheat when i sat and idled for too long now i dont have that problem.

I believe in order to get the two fans to be temp controlled you would have to learn assembly programming and program your ECU to have two temp controlled fan switches.

 

I understand what you are saying, but it doesnt make sense. I want my fan to come on at low speeds, or 0 speed, not high speeds. When I am going 60mph i dont want the fans on. The airflow to the front of the engine is enough to keep it cool. No need to run the fans at high speed. So I think the constant should be a max speed upto which the fan will run. No need to run more electrical load if not needed.

Well I think what some folks have done, is use some extra output in the 165 ecm, which is not used, or removed, to turn on the second fan. But yu would need to get into the hac, and know what you are doing.

 

Mike, I double checked the $6E and unfortunately, there is only 1 fan control settings (though you have a second temp setting that depends if the AC is on or off ... hint).

But, unlike the $8D SD computer which DID have two separate logic in the calibration for controlling Fan1 & Fan2 (and then some clever person found the proper pin to control Fan2); the $6E does not have separate logic for Fan1 & Fan2.

The best you can do (other than using a lower temperature fan SW for Fan2 as most people do), you can either have Fan2 jumped with Fan1 (like you were suggesting) or wire a "manual switch" to control Fan2.

I believe Willie did an article on controlling Fan1 & Fan2 for the MAF system a number of years ago. It is either in the FAQs or one of the Tech Articles.

 

Yea that what I thought, Grim. You just confirmed it. I allready have 2 fan control switches installed, and a lower turn-on switch in the radiator for fan2. And yes I got most of my ideas from Willie's articles many years ago. I wired one of the extra idiot lights in the dash to come on when the Hayden switch turns on Fan2. The only thing is I mounted the 2 switches under the hood near the battery, so I cannot control them from the cockpit....but that is going to change soon....

At least I get lots of Q's asking what those switches do....

 

What pin is fan2 on?? I thought they were wired together!

-- Joe

 

$8D, 730 is F8 with request input on D12.
Back to the 165 discussion.

 

I thought it was E8(dark green wire/white stripe) ??

 

On the '7730 with the $8D code, E8 is fan 1, F8 is fan 2.

RBob.

 

So then my next question is: If i connect D12 and F8 with a jumper does the secondary fan switch need to be hooked up? I imagine so,but others say its not ecm controlled? I have the wire that used to go to the switch connected to a 12v manual switch in the car and the other end grounded so its all manual.

 

Jumping D12 & F8 together will put fan 2 under ECM control. I'd keep the head temperature switch just for back up, but it is not required.

RBob.