Electrical Gremlins (1 Viewer)

[CR79BJ40B]

Howdy,

I just traded for a 1987 BJ70. As to be expected with any vehicle that's 28 years, its got gremlins. Well not full on, more like "what's this plug go to" kind of gremlins.

For example, on the pax side, the fuel sedimenter isn't plugged in, truck runs fine. On that same harness, there is another round female plug but nothing within reach of it to plug into (white, white/black, black, black/red). There is another plug, same type on the other side as well, close to the starter.

I've tried looking at diagrams but coming up short.

Thanks in advance

 

[JuanJ]

Hello,

Some plugs are used, some are not. This is because 70 Series trucks have a lot of options when it comes to electrical equipment, and the same harness is used for different models.

If you look closely at the wiring diagrams, the plug type is indicated along the circuit. It is not a big picture, and it is easy to miss.

Unused plugs that come to mind are side fender indicators, power outlet box and air filter in the engine bay. Unused plugs in the dash that come to mind include fog lights, rear fog lights, rear wiper/washer and rear heater. This is not a full list.

You should look for hacked/spliced connections along the harness, as well as non-factory wiring and ground points. Creative mechanics run ground cables to wherever they want in the body or engine, a practice that produces a lot of hard to kill gremlins. Splices/hacks and non-factory wires create gremlins as well.





Juan

 

[CR79BJ40B]

Thanks man. I didnt even think of that, but it reminded me of a harness I bought for my 40 which had all the extras.

I just got the 70 yesterday, so tomorrow will be the walk around (more so), like figuring out if the glow plug relay works as i dont hear any clicking like the 40 nor is there a back turn on the ignition.

 

[Gubbtratt1]

Thanks man. I didnt even think of that, but it reminded me of a harness I bought for my 40 which had all the extras.

I just got the 70 yesterday, so tomorrow will be the walk around (more so), like figuring out if the glow plug relay works as i dont hear any clicking like the 40 nor is there a back turn on the ignition.

There's two glow plug relays, the indicator light is on with the first one, then it switches to the second one which is supposed to be active while you start it. The glow plugs are automatic, there's a timer that decides how long each relay should be on based on the coolant temperature.

 

[CR79BJ40B]

There's two glow plug relays, the indicator light is on with the first one, then it switches to the second one which is supposed to be active while you start it. The glow plugs are automatic, there's a timer that decides how long each relay should be on based on the coolant temperature.

Is there a switch at the ignition to initiate the relay?

 

[Gubbtratt1]

Is there a switch at the ignition to initiate the relay?

There's no separate switch if that's what you mean. The glow system always turns on when you turn the key to ignition.