LS Swap and Electric Fans
03-06-2018, 08:54 AM
#1
LS Swap and Electric Fans Hello. I have a '94 300ZX with a LS1/6 speed swap. The electric fans used to work fine, but after sitting for a while, they do not work anymore. I have verified all relays and fuses are good...and the fans are still good. But, the PCM will not turn them on. I get no ground signal from the PCM. I manually try to turn them on via the scanner and they still dont come on. I thought maybe it was a bad PCM, so I tried a different one and still nothing. With the other one I tried, it had a different tune in it that I didnt change. I just manually tried to turn them on via the scanner and still nothing. Im at a loss on this one, so I would appreciate any guidance offered! Green wire from #42 pinout is the one going to the relay to trigger the fans. Perhaps a reflash of the tune would help? I doubt that though, as I should just be able to turn them on manually through the scanner on HPT, or am I missing something?
03-06-2018, 09:03 AM
#2
Restricted User
Jump the positive and negative of the relay straight to the battery (remove the wire from Pin #42 and jump the entire wire to the negative battery terminal) to make sure the fuse/relay/fans/wires themselves are good. Then make sure the PCM grounds are good.
03-06-2018, 09:45 AM
#4
Restricted User
Different parts of the PCM's PCB is grounded in different spots. They're not all connected inside. Certain bad grounds can cause certain functions to act incorrectly, mainly 12v/ground.
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03-06-2018, 01:14 PM
#8
On the relay, I ran a jumper wire from the battery power straight to the slot the fans are wired to and they came on. For the ground coming from pin 42, I checked with a volt meter and it isn't getting a ground signal. It doesn't even show a ground signal when I turn the fans on manually through HP Tuners on the Scanner. I put a meter into the actual pinout as well on the PCM and it didn't show a signal.
03-06-2018, 01:19 PM
#9
Restricted User
On the relay, I ran a jumper wire from the battery power straight to the slot the fans are wired to and they came on. For the ground coming from pin 42, I checked with a volt meter and it isn't getting a ground signal. It doesn't even show a ground signal when I turn the fans on manually through HP Tuners on the Scanner. I put a meter into the actual pinout as well on the PCM and it didn't show a signal.
03-06-2018, 01:47 PM
#10
Instructions for removing Pinout
No tool needed really needed, maybe a small screw driver or a pick to push in the locking tabs way from the Blue/Red cover (side) and the pins.
First remove the Gray cover on the back side. 3 tab on each side.
Once the colored covers are off, Use a pick to push the white locking tab away from the pin (what locks the pin in) so that then pin/wire will slide out. You can either pull or push them out.
Once you do that, the pins will just slide out if you push or pull the wire/pin. Might have to use the pick to push the white locking tab on the pin side away so that pin/wire will slide out;
03-06-2018, 02:05 PM
#11
Restricted User
7mm socket to take wiring connector off of PCM. Take small flathead screwdriver and pop off the blue connector that has pin 42 in it (you don't even have to remove the pin from the PCM connector). Jump a wire from the end of that pin to the battery negative. If the fans kick on, you have likely have a short in the PCM or in a ground elsewhere. The whole thing should take maybe 5 mins.
03-06-2018, 02:33 PM
#12
7mm socket to take wiring connector off of PCM. Take small flathead screwdriver and pop off the blue connector that has pin 42 in it (you don't even have to remove the pin from the PCM connector). Jump a wire from the end of that pin to the battery negative. If the fans kick on, you have likely have a short in the PCM or in a ground elsewhere. The whole thing should take maybe 5 mins.
03-07-2018, 12:07 AM
#16
Man, you guys are good! Turns out a bad wire in the harness. BUT, now I have other issues...that weren't prevalent until now. I went to start the car and no fuel pump. UNBELIEVABLE. I didn't have this issue until I started fixing the fan, and I don't know what I did. Long story, but when I was monkeying around to put relay back in for fuel pump - I hit the power lead to the chassis and it blew the fuse and I replaced it. But, it doesn't kick on. I am getting power to the relay from the key and getting power to relay from battery and I hear the relay click when I turn the key on. The car has an external (for lack of better words) relay for the fuel pump itself. But, it isn't sending a signal from the relay to the power wire of the pump. I can jump the relay and the pump comes on, so it isn't fried. I try to turn the fuel pump on manually through HPT and I hear the relay click, but the pump doesn't come on. Again, I think it's something with the wiring from the PCM. Whether I messed it up, I don't know. I'm looking for ideas on how to check that. The car starts and runs fine when I bypass the relay from the battery. Again, thanks for all of the help. I was stoked to have the fans fixed - but now am in a heap more of trouble.
03-07-2018, 06:52 AM
#18
First thing to try is to pull the relay and jumper your Battery 12v and your pump side together at the socket (should be pins 30 and 87) to see if the pump turns on. You mentioned you can hear the relay clicking over so I'm guessing your issue will be your 12 volt supply to the pump relay.
03-07-2018, 08:53 AM
#19
First thing to try is to pull the relay and jumper your Battery 12v and your pump side together at the socket (should be pins 30 and 87) to see if the pump turns on. You mentioned you can hear the relay clicking over so I'm guessing your issue will be your 12 volt supply to the pump relay.
03-07-2018, 12:35 PM
#20
If a jumper between 30 and 87 turns on the pump then the relay itself could be bad. If you've got a multimeter you can apply power and ground to pins 85 and 86 of the relay and when it clicks over meter between pins 30 and 87. You should have near zero ohms between them when energized.