Jeep - what is that thing under the hood?

[Betty]

Question for jeep people and/or mechanics. This photo is under the hood, over by the battery. See that black plug thing over on the right? It wasn't plugged in... for how long? If we follow the wire, it goes into a wire harness. Plugging it in doesn't seem to have any effect one way or another. What is it?

[DreadPirateRoberts]

The black plug is a relay. What year is the jeep? TJ ?

It doesn't look stock. What has been added aftermarket? winch ? lights? alarm?

[Betty]

It's an 03 TJ. Winch added... or at least it was until it it was broken a few weeks ago.

Someone else suggested it was perhaps, for a rear window wiper for a hard top (which we don't have) or fog lights. We aren't the original owners - maybe it had something like that before we got it.

[Betty]

My husband thinks it's stock something as it appears to be part of the factory harness.

[DreadPirateRoberts]

Do you have the owner's manual? Do they make any mention of daytime running lights?

[Betty]

Originally Posted by DreadPirateRoberts

Do you have the owner's manual? Do they make any mention of daytime running lights?

He shook his head and made a sort of incoherent noise which I take to mean no. ha ha ha

He does have a Haynes manual which shows it but doesn't say what it's for apparently.

[Moonliner]

I called in the heavy artillery. We should have our answer shortly....


Or even faster....

Originally Posted by Guy that knows ****

That's the ECU - the "Engine Control Unit". The unit converts the distributor's magnetic signal to the necessary signal to fire the coil. If it fails the jeep will not run. You can get a replacement at any major parts store by asking for the ignition control module. If you hook up an HEI (High Energy Ignition) system you will not need it at all and can get rid of it and all the associated wiring (aside from the main igition feed wire that will need to be hooked up to the HEI distributor).

[Moonliner]

Woops. I think this might be the better answer...

You talking about the ones attached to the silver ECU or the one that is by itself on the painted surface? Because that one (on the painted surface) is just a fog light or some such thing relay. Aftermarket it looks. Wouldn't surprise me if the device it was attached to is now long gone.

[Betty]

First off - Reddit has a jeep forum! TIL!

And yes - talking about the the one off by itself on the right. Hey - at least it wasn't something important that's been unplugged.

[DreadPirateRoberts]

When the relay is unplugged, does the cigarette lighter work? How about the heater/ac?

Are there any check engine lights on?