1978 FJ40 turn signal replacement… 3-wire to 2 wire? (2 Viewers)

[RollBar]

I’m doing my best over the past few days to search for anything that may answer my question, but in the mean time, will post this here in case anyone has a quick suggestion. I’m replacing the front turn signals on my ’78 FJ40. Bought two new ones from SOR and have physically installed them, but the strange thing is that the left side one comes with 3 wires, whereas the old one only had two. So, I need to figure out how to wire that up. Also, on the right side, the PO did some “custom wiring” such that I don’t have original colors any more, to hook up to the new light. Is there a way to test to see which is correct, and/or, is it a problem to hook it up “wrong”… meaning, it just won’t work, vs it will damage something? Thanks.

 

[RollBar]

Followup… for anyone who may need the same info: My ’78 is a 10/77, which is “supposed” to be after they switched to 3-wire on the left front turn signal, but mine must have used some pre-cutover parts… a “Franken-40” so I’m told I just need to figure out which one of the 2-wires on the vehicle lights two bulbs (side marker + running light) on the left side, and then hook up 12v (and ground, to the threaded mounting post, since there is no separate ground wire for either side… uses fender metal for ground, I guess…), and see which 2 of the 3 wires I need to just pigtail together… with the other one being the signal bulb. We shall see...

 

[mattressking]

Put a multimeter on the + positive lead, ground the other lead then you should see the following:

+12v on meter when you activate blinker/flashers
+12v on meter when you activate parking/running lights

If you test the 3rd wire on chassis harness, select the continuity setting on multimeter and you can verify ground.

Then connect turn signal assembly accordingly. Make sure you have a good ground on turn signal housing if not using 3rd wire on chassis harness. You could run a separate ground wire also if yould like off the turn signal housing and connect to 3rd wire (ground).

 

[RollBar]

Put a multimeter on the + positive lead, ground the other lead then you should see the following:

+12v on meter when you activate blinker/flashers
+12v on meter when you activate parking/running lights

If you test the 3rd wire on chassis harness, select the continuity setting on multimeter and you can verify ground.

Then connect turn signal assembly accordingly. Make sure you have a good ground on turn signal housing if not using 3rd wire on chassis harness. You could run a separate ground wire also if yould like off the turn signal housing and connect to 3rd wire (ground).

Thank you, Nate. I will do that. And I was thinking about creating a ground wire on each side, since between the thick coat of aftermarket paint and the undercoating underneath, it may not be grounding to the frame properly. I appreciate the guidance...

 

[ToyotaMatt]

I’m doing my best over the past few days to search for anything that may answer my question, but in the mean time, will post this here in case anyone has a quick suggestion. I’m replacing the front turn signals on my ’78 FJ40. Bought two new ones from SOR and have physically installed them, but the strange thing is that the left side one comes with 3 wires, whereas the old one only had two. So, I need to figure out how to wire that up. Also, on the right side, the PO did some “custom wiring” such that I don’t have original colors any more, to hook up to the new light. Is there a way to test to see which is correct, and/or, is it a problem to hook it up “wrong”… meaning, it just won’t work, vs it will damage something? Thanks.

so you have the received the updated modern non-usa polarized 3-wire front combination lamps from SOR , this is a GOOD thing , the only main difference is the side square oarnge lens will NOW be a turn blinker , and NOT a on all the time running side marker , i ALWAYS re-wire this to match the usa spec. lamps ....

the cheezy usa-spec. ones rely on the threaded post and its large Hex nut and spring washer for the NEG- Ground Circuit signal , on each side of your 1978 FJ40 running among the aprons there is a white wire w/ black tracer stripe , they DO NOT run as far past the coil and igniter , and the VACUUM VSV emissions box , but never the less you can reply on them , add on to them , using the same Toyota color code wire , and feed dedicated home-run ground wires to each new lamp ....

the link below has enough OEM male and female bullet connectors to refresh all your old 1978 harness side ones and also ADD the new needed ground wire circuits chassis harness side too ....

- if you make sure to ADD to the NOTES , during check out : simply say " Remember 10 feet Ground Wire "
- ill spin you off 10 feet of the 16ga OEM yazaki ground circuit wire and include it in your box , no problem


- matt

OEM TOYOTA GENUINE Parts YAZAKI JAPAN Spec. GREEN TINT SHEATHS TIN Plated Marine Grade SOLID Brass terminals Terminal Bullet Connectors Connector 10 pack KIT - VintageTEqParts.com

- OEM TOYOTA GENUINE Parts - YAZAKI JAPAN Spec. - GREEN TINT Sheaths - Bullet Connectors Connector - 10...

vintageteqparts.com

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[RollBar]

Hey Matt… thank you. I’m not sure if I got the exact ones you reference, but I did get them from SOR… I did buy the after market ones. But the front left has 3 wires, while the front right only has 2. I do like the idea of running a “real” ground wire. I just picked an assortment of bullet connectors and several colors of wire, so I’m going to give that a shot. I had a ground problem before, with signal blinking once then “stuck”, but the old signals were beat up anyway, so starting with new ones, then going through each connection. Too cold here for my arm out the window all the time when turning.