anton74 Posted January 19, 2010 Report Share Posted January 19, 2010 Hello, I am thinking about adding a manual override switch for one of my radiator fans. What is the best way to wire the switch? I know that grounding the fan relay should activate the fan, but this could probably set the error code and turn on the SES (service engine soon) light. Another possibility could be adding new relay, wiring its contacts in parallel to the existing fan relay. Does anybody have this kind of switch? Thanks, Anton. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted January 19, 2010 Report Share Posted January 19, 2010 I don't think manually overriding the fan would trip the SES light. Very simply, you can probably just run a hot and a ground with an inline fuse for safety. Someone correct me if I'm wrong though. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 19, 2010 Report Share Posted January 19, 2010 better be a slow acting fuse, since as a fan starts to spool up, it pulls a LOT of amperage. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted January 19, 2010 Report Share Posted January 19, 2010 better be a slow acting fuse, since as a fan starts to spool up, it pulls a LOT of amperage. What would you suggest? Do they make such a thing? If it were me I'd just hotwire it, and call it a day. But I was trying to give good advice, :lol: Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 19, 2010 Report Share Posted January 19, 2010 they have slow-acting fuses out there. it could work perfectly fine, but honestly, if i would even do it at all, i would run a bypass through a rocker switch after the relay that allows the ECU to command it on when it feels it is necessary, and when the rocker is thrown on, it forces the fan on. Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted January 19, 2010 Report Share Posted January 19, 2010 I did something similar on a Grand Am once I had that had screwed up fan relay wiring. I used a relay to trigger the fan, with the power to activate the relay going through a switched accessory spot on the fuse panel, so that the fan would automatically be switched off when the car was not in the RUN position, in case I forgot to turn the switch off. That power went through a lighted rocker switch, so I could control when it was on. I ran a wire from the battery terminal, through a fuse to the relay, so the rocker switch only had the relatively low current to activate the relay on it. they have slow-acting fuses out there. it could work perfectly fine, but honestly, if i would even do it at all, i would run a bypass through a rocker switch after the relay that allows the ECU to command it on when it feels it is necessary, and when the rocker is thrown on, it forces the fan on. Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted January 19, 2010 Report Share Posted January 19, 2010 I've added manual switches to the fans before. On my old Z34, I had two switches, one for each fan respectively. I added two new relays to the system, and wired them parallel to the factory ones. I never got an SES light from it. --Dave. Quote Link to comment Share on other sites More sharing options...
anton74 Posted January 19, 2010 Author Report Share Posted January 19, 2010 I've added manual switches to the fans before. On my old Z34, I had two switches, one for each fan respectively. I added two new relays to the system, and wired them parallel to the factory ones. I never got an SES light from it. --Dave. How did you splice into the factory wiring? I mean the wires from switching contacts of the fan relay. These wires pass a lot of current. Quote Link to comment Share on other sites More sharing options...
anton74 Posted January 19, 2010 Author Report Share Posted January 19, 2010 I've found the following: http://www.backinblackgp.com/Manual_Fans.htm Seems like there is no need to modify the high current wiring, only splicing into the PCM control wiring will do. Seems somewhat complicated though Quote Link to comment Share on other sites More sharing options...
sloick Posted January 19, 2010 Report Share Posted January 19, 2010 on an old camaro i could pull one of the ac wires and it would fool the ecu to turning the fans on. swith in on position everything was factory, computer still worked the fans normal. switch off would turn the fan on. i cant remember what wire it was. it worked great. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 19, 2010 Report Share Posted January 19, 2010 on an old camaro i could pull one of the ac wires and it would fool the ecu to turning the fans on. swith in on position everything was factory, computer still worked the fans normal. switch off would turn the fan on. i cant remember what wire it was. it worked great. probably A/C pressure sensor, though i'm not entirely sure if that would work in this situation... Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted January 19, 2010 Report Share Posted January 19, 2010 the way I did it, was like it was it's own complete separate circuit. I ran 10ga wire from the relays to the fans for + power to the fans (split some of the insulation from the original fan wires, and soldered my wires in) and 10ga wire to the relays from the battery, with a (I think 20amp) blade fuse in-line from an old car-stereo wiring kit. The relays were always hot, but needed to be grounded to activate, and the switches I had in the car supplied that ground, to complete the circuit. It was fairly simple, and worked well. --Dave. Quote Link to comment Share on other sites More sharing options...
sloick Posted January 20, 2010 Report Share Posted January 20, 2010 on an old camaro i could pull one of the ac wires and it would fool the ecu to turning the fans on. swith in on position everything was factory, computer still worked the fans normal. switch off would turn the fan on. i cant remember what wire it was. it worked great. probably A/C pressure sensor, though i'm not entirely sure if that would work in this situation... sounds right. Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted January 20, 2010 Report Share Posted January 20, 2010 Whoa Whoa... hold up. To wire in a fan switch all you have to do is apply ground to pin 86 on the bottom of the relay. You don't even have to mess with positive at all. On some cars though, if you leave the switch on after you turn the car off, the fan will keep running. On my tgp, I've run a constant ground to the secondary fan in front of the intercooler. I turns on at key on, runs constantly, and turns off with the car. If I ran a constant ground to the primary fan, it would stay on after the car was turned off. Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted January 20, 2010 Report Share Posted January 20, 2010 Pics: Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 20, 2010 Report Share Posted January 20, 2010 To wire in a fan switch all you have to do is apply ground to pin 86 on the bottom of the relay. You don't even have to mess with positive at all. that's what i was suggesting. just use a rocker/toggle switch and it will allow you to force the fan on and allow the ECU to turn it on as well... Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.