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Mike, Technician
Category: Jeep
Satisfied Customers: 39198
Experience:  Tech Expert
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Hello, I need to locate an

Customer Question

Hello, I need to locate an [ under bonnet ]ignition controlled positive feed suitable to supply recently fitted all day running lights using an auto relay designed to switch the lights off when the side lights are switched on. I can not locate a wiring diagram from anywhere. All wiring installed, just need an ignition fed positive supply connection preferably close to the fuse boses. The vehicle is a 2008 Grand Cherokee Overland Many thanks Dick XXXXX

Submitted: 3 years ago.
Category: Jeep
Expert:  Shantal-Mod replied 3 years ago.
Hello Dick,
I'm Shantal and I'm a moderator for this topic.
We have been working with the Experts to try to help you with your question. Sometimes it may take a bit of time to find the right fit.
I was checking to see if you had already found your answer or if you still need assistance from one of the Experts.
Please let me know if you wish to continue waiting or if you would like for us to close your question?
Thank you,
Customer: replied 3 years ago.

Hello Shantal,

Thank you for checking but I still need assistance. Ideally from someone who is familiar with Jeep electrics. I'm sure the answer is very simple but I don't want to cause a major problem with my car should I get it wrong.

Due to a hospital procedure I will not be contactable from 14th August until 16th August inclusive.

Many thanks


Expert:  Shantal-Mod replied 3 years ago.
Hello Dick,
Thank you for getting back to me and providing more information on the situation. I will continue to look for a Professional to assist you.
Thank you for your patience,
Expert:  Mike replied 3 years ago.
Hello Dick and Welcome -

My name is ***** ***** have been asked to help you here with this issue.

So - you need as you say "an ignition fed positive supply connection preferably close to the fuse boxes"... ..." under bonnet ignition controlled positive feed "....

Jeep / Chrysler are known for being very hard to get wiring diagrams for so Im not surprised you have been struggling - they are the worst to be honest !

Now - with this-- you could use for example fuse no. 37 in the main engine bay fuse box- this is an ignition circuit fuse... you could use that ... but - Im going to suggest something different.... and this is because on these later vehicles, that have whats known as CAN enabled systems, piggy backing extra circuits in - to any fused circuit can create problems... eg - the computers detect extra circuits and cause shut downs etc - Some you can have programmed to accept extra circuits but this is a dealer job and obviously costs money... So what I would suggest is this... remove the cowling behind the steering wheel - and access the wires that go directly to the ign switch.

Then use a meter - or a 12v test light - and probe each of the wires making a note of which is live ( perm feed ).. and which are not - Ign OFF.

Then switch the ign ON - and re check the same way... when you get a light / reading from a wire that previously was dead - you then know that is the one you need... ie, "ignition controlled pos feed"... and you can connect to that wire to feed your circuit. Fit an in line fuse to your extra feed wire -and thats a safe job done. It really doesn't take long at all to do as above and is the best way to be honest with you...for the reasons outlined above.

For the above - I have uploaded this for you HERE.

Im very pleased to have helped you - Do let me know if you need anything more --

*** Meantime - - >>>> Please do click on the "OK/ Excellent ratings" for me - Thank you in advance for that...

You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..

Kind Rgds, MIKE.
Customer: replied 3 years ago.


Thank you for your response but one of the reasons I was looking for an underbonnet connection is so I could tap into an identifiable cable that has sufficient capacity to take the extra loading. I had thought about your suggestion but knowing how the electric system on this Jeep will shut down when it is not happy with a particular configuration then I was not going to take the chance by going in blind. No disrespect but I went to this site because it claimed to have a Jeep expert on hand to assist. What I am hoping to discover is the colour of the cable that will do the job. The power supply line is already fitted with a 7.5 amp fuse feeding into a12v relay switch.

A friend of mine did something very similar. All worked well for several months and then the problems started; various items failed to operate after the initial switch on process. It could be the windows one day, the radio and sat nav the next or upon start-up the the audio system would fail. He removed the wire from the ignition,had the on- board processor re-programmed and all was fine. Re-connected the wire several weeks later and his problems started all over again.

So you can see why I want to get this right. Jeep dealerships are few and far between in Mid Wales so I don't want to take any chances.


Dick Powell