Author Topic: Wire Up Ignition for Electric Fans  (Read 271 times)

Offline psyguy23

  • Newbie
  • Posts: 15
  • Newbie
Wire Up Ignition for Electric Fans
« on: June 10, 2018, 04:22:02 PM »
Ok. Hoping this post will get some answers for myself and others.

1983
K1500
5.7L

Due to a leaking water pump, I recently replaced the entire cooling system and have upgraded to a 3 row aluminum radiator with aluminum shroud and dual 12” electric fans. My challenge and question is Where do I hook up the ignition or fan switch wire?

I would like the fans to turn on when the thermostat sending unit, that came with the electric fan kit, reaches its temp of 200 degrees and off when either the temperature sending unit reaches 185 or whenever the ignition is off, whichever comes first.

The Fail Safe thermostat is rated at 190. The temperature sending unit for the fan relay is installed on top of the thermostat housing water outlet. The relay for the fan kit is rated at 60A and the circuit breaker is rated at 30A.

I have have all the wiring figured out except Where do I hook up the ignition or fan switch wire?

Thanks in advance for all the help. I attached pictures.

Yes. I still have the mechanical fan attached. Drive this beast daily.

Matthew.

https://www.amazon.com/photos/share/6MeQuYOwvTSyg8Kr2Ru8h4RLbpV3RqJZ1xM6mZ1U3ED
1983 GMC K1500 4x4 5.7L
Daily Driver, Long Term Project
SMOG is no problem.

Offline VileZambonie

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 16890
Re: Wire Up Ignition for Electric Fans
« Reply #1 on: June 10, 2018, 07:44:56 PM »
If you are energizing the relay with key on b+ you will go to an open spade terminal in your fuse block that is either energized with key on or engine running.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

Offline psyguy23

  • Newbie
  • Posts: 15
  • Newbie
Re: Wire Up Ignition for Electric Fans
« Reply #2 on: June 10, 2018, 08:40:32 PM »
Vile. Thanks for the response.

So run the ignition switch wire from the relay, through the firewall, to the fuse box under dash and bare wire to the fuse terminal for ignition?

My electrical skill is limited so I am just being very specific.
1983 GMC K1500 4x4 5.7L
Daily Driver, Long Term Project
SMOG is no problem.

Offline 75gmck25

  • Registered Users
  • *
  • Posts: 210
  • 1975 GMC K25 Camper Special, 350/TH350/NP203
Re: Wire Up Ignition for Electric Fans
« Reply #3 on: June 11, 2018, 07:26:24 AM »
Just to make sure you understand the typical wiring for a fan relay.  However, if you bought a commercial kit it may have some variations.
- The main, high amp power feed to the relay is where the circuit breaker goes, and its probably best connected to the junction that is mounted on the firewall next to the brake booster, or directly connected to battery positive.  This is what powers the fans, through the fan relay.

- The relay should also have an ignition-on terminal, which ensures the fans turn off when the truck is off.  That is what Vinnie described above.  This is a low amp wire, so it can be powered by nearly any ignition-on source.

- There will also be wire running to the temperature sensor, which is the fan activation wire.  This turns the fan on/off at the set temperature.

- There will also be a ground that should be connected to the radiator support or other good metal ground.

Once you get it all wired up, you should be able to turn the truck on (not started) and when you ground the wire running to the temp sensor it should turn the fans on.  If that works, reconnect the wire to the sensor, which will now ground it at the set temperature (200 degrees, etc.), and turn the fans on.

Bruce

Offline psyguy23

  • Newbie
  • Posts: 15
  • Newbie
Re: Wire Up Ignition for Electric Fans
« Reply #4 on: June 12, 2018, 08:37:36 PM »
Ok. Got it all wired up and tested like Bruce suggested.

One wire from relay (short red) goes to blue power wire on fans.

Another wire from relay (long red) is hooked up to the battery with 30A circuit breaker in the middle.

3rd wire (black, temp sensor wire, ground) is grounded to the battery temporarily for testing.

Last wire is the brown (ignition wire) from the relay. When I touch this wire to the positive battery terminal the relay clicks and the fans spool up.

Main question remains. <b>Where do I hook up this brown wire?</b> Now I know where my fuse box is on the interior and the 15A fuse. And I can see from the engine bay where the wiper motors are wired up. So I safely assume the large square box under it with the 3 wire looms coming out of it is the wiring for the fuse box?

So. <b>Which wire do I tap into?</b>

I apologize that my questions are so basic.
1983 GMC K1500 4x4 5.7L
Daily Driver, Long Term Project
SMOG is no problem.

Offline VileZambonie

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 16890
Re: Wire Up Ignition for Electric Fans
« Reply #5 on: June 12, 2018, 08:49:22 PM »
You tap in on the inside at the fuse panel not in the engine bay. Look at your fuse panel, find an ign spade to connect to.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

Offline Rapid Roy

  • Frequent Member
  • **
  • Posts: 298
  • Euless, Texas
Re: Wire Up Ignition for Electric Fans
« Reply #6 on: June 12, 2018, 09:33:48 PM »
See if this is any help.

1974 Cheyenne 10 LWB 350/TH350/AC/4 BBL Quadrajet

Offline 75gmck25

  • Registered Users
  • *
  • Posts: 210
  • 1975 GMC K25 Camper Special, 350/TH350/NP203
Re: Wire Up Ignition for Electric Fans
« Reply #7 on: June 13, 2018, 08:09:21 AM »
If you look at where the speedometer cable comes through the firewall, there is a large rubber grommet and there should be some play/flexibility in the rubber so that you can slip the brown wire through there and connect to one of the -ignition-switched spade terminals on the fuse box.

Other folks have also tapped into one of the wires for wipers, since it is also ignition switched.  However, I don't know off hand which wiper wire is the switched power. 

Bruce