Fan Relay ?; edumacate me plz!
05-25-2012, 02:19 PM
#1
Fan Relay ?; edumacate me plz! My wiring harness included fan relays and I just want to make sure I understand how they work. You'll have to look at the attached picture to make sense of the following questions. I understand relays as taking a large amp line in and having a large amperage line out, but a separate line with small amps coming in to turn on (connect) the two large lines on; this keeps the large current from not being in the length of the entire circuit, so ideally the relays are closer to the battery source. If this is not a good understanding of relays, plz correct.
In my case, the fan relays have two large orange power lines coming into them from the main engine harness (taking power from the large red line coming off the horn relay), and both have a fuse prior to the relay. Then they go down to yellow lines (much smaller wire in) and the power out is the purple line (again a small line) which then goes into a large orange line which also has a fuse). These two orange lines connect to the fans. My question is why does the fan power coming into the relay and out of the relay go to a smaller wire. I'm wondering if this is a fusible link. But if a fusible link, why does it also have a fuse both in front and after the relay? I'm also trying to get my wiring harness guy to explain, but thought I'd ask you all as well. I'm just trying to understand relays since I've been told I need to add one for my power seats (which I may or may not do).
Thx!
In my case, the fan relays have two large orange power lines coming into them from the main engine harness (taking power from the large red line coming off the horn relay), and both have a fuse prior to the relay. Then they go down to yellow lines (much smaller wire in) and the power out is the purple line (again a small line) which then goes into a large orange line which also has a fuse). These two orange lines connect to the fans. My question is why does the fan power coming into the relay and out of the relay go to a smaller wire. I'm wondering if this is a fusible link. But if a fusible link, why does it also have a fuse both in front and after the relay? I'm also trying to get my wiring harness guy to explain, but thought I'd ask you all as well. I'm just trying to understand relays since I've been told I need to add one for my power seats (which I may or may not do).
Thx!
05-25-2012, 03:48 PM
#2
Also, I have a fuel pump relay off the engine harness, but I'm using the racetronix kit and wiring upgrade (http://www.racetronix.biz/mmWEBSTORE/Images/BLT1.jpg) which has its own relay; any reason I need to use the one off the ECU harness? Otherwise I can use the fuel pump power off my KWIKWIRE harness and the relay from racetronix.
05-25-2012, 04:04 PM
#3
The small wire from the PCM and otherwire go to +12V to opereate a low curent coil to close the high current relay contacts. The larger wires handle all the current from the red power wire through the relay to the fan. The coil and high current terminal wires are diagonally placed when seen at the bottom of the relay.
Similar pinout:
http://faqlight.shopower.com/hella-f...ated-relay.jpg
Similar pinout:
http://faqlight.shopower.com/hella-f...ated-relay.jpg
05-25-2012, 04:07 PM
#4
The way your fuel pump relay is wired is the same as GM uses. When the engine stops turning in the event of a severe wreck, the crank no longer sends pulses to the PCM and it shuts off the fuel pump relay. Not sure if your aftermarket pump harness has that capability.
05-25-2012, 04:34 PM
#5
AKNOVAMAN, can you also explain why you go down to a smaller gauge wire into the relay? Is that for a fusible link? if not, why not go with a larger line right into the relay? If so, why have that and an inline fuse?
THX!
Last edited by Goldhawg; 05-26-2012 at 07:29 AM.
05-26-2012, 01:57 AM
#6
I have absolutely no idea why you have smaller gauge wires going into the relay. Who put them there?
Your fan relays are triggered by a ground provided by the ecu. You should provide the + switching voltage full time since the ecu is programmed to keep the fans on if the temp is too high even after you switch the engine off.
Unlike the fans, the ecu provides a + 12 V signal to the fuel pump relay. Wire it that way through the relay.
Your fan relays are triggered by a ground provided by the ecu. You should provide the + switching voltage full time since the ecu is programmed to keep the fans on if the temp is too high even after you switch the engine off.
Unlike the fans, the ecu provides a + 12 V signal to the fuel pump relay. Wire it that way through the relay.
05-26-2012, 07:29 AM
#7
I have absolutely no idea why you have smaller gauge wires going into the relay. Who put them there?
Your fan relays are triggered by a ground provided by the ecu. You should provide the + switching voltage full time since the ecu is programmed to keep the fans on if the temp is too high even after you switch the engine off.
Unlike the fans, the ecu provides a + 12 V signal to the fuel pump relay. Wire it that way through the relay.
Your fan relays are triggered by a ground provided by the ecu. You should provide the + switching voltage full time since the ecu is programmed to keep the fans on if the temp is too high even after you switch the engine off.
Unlike the fans, the ecu provides a + 12 V signal to the fuel pump relay. Wire it that way through the relay.
