Hi, I am new to this forum. I recently swapped the OE head unit in my 99 4 RUNNER for an aftermarket stereo. I have done this many times on other vehicles and no problems. After the install the new head unit worked fine. 2 weeks later it has just stopped receiving power. I have checked all fuses and they are all fine, I still have power in my clock, cigarette lighter and the dome light. In fact everything in the truck works as required. I swapped the new head unit for the original OE unit and this is receiving no power either (thus i have ruled out head unit failure).When i installed the new unit i simply bi passed the amplifier behind the console. Does anybody know if there is an inline fuse solely for the radio or are my fears correct and does this point to melted cables ??

 

You had the correct adapter plug and just plugged the new unit into the Toyota Harness.

You have checked that the radio fuse is good and that it is tight in the socket so it makes good contact.

Does your new unit have a separate ground or does it also ground via the stock harness.

 

I bought a harness solely for toyota's. This plugged into the stock harness. I had to connect the wires but this is done correctly as i have triple checked it. There are no wires for earthing the radio supplied so i assume it is pre wired through the harnesd. ( surely if an earth was an issue it would have never worked?)

 

Now I have the Toyota Electrical diagrams for 1998 .

No other fuses but for the dome light fuse and the acc fuse.

You have not broke out your Meter .

Did anything happen when it quit ?? Like hitting a big puddle or a huge bump.

The smell of wire insulation burning??

Sounds to me like you lost your ground which would explain why the stock one also does not work.

Did you have any of the wires where they could rub on anything and rubbed through after this time.

Check if your getting battery positive 12 vdc plus and a ground out of the vehicle harness and go from there...

If your not I am sure you can get it working from there.

If you cooked any wires you should be able to see them and I would guess other things may not work which appears not to be the case.

 

Thanks for the feedback. When the unit failed to work it hapened overnight. Sunday night it worked, monday morning it didnt. I have no meter to test power source as all my tools are in another country. I have not smelt any burning odour. I will check the earth tomorrow and hopefully find the error. Can u tell me where the ground is located according to the diagram ?

 

Read the posts, I'm thinking these guys got it, you can always hook an aftermarket stereo to the car battery to make sure it works , connect red and yellow together, and run it to the positive terminal, black to negative, if the unit works it will turn on. Be careful with the other wires, tape em up first, so they can't touch each other, or metal, like the front core support. If it turns on, your problem lies inside the dash and your unit is not a big paper weight. If you don't have a tester, hook up black out of decks wires , and hook it to the cars wiring ground in the dash, find constant power , connect yellow and red to constant power . If deck powers up disconect red and yellow, and find the car harness acc wire and check that it kicks on when the key is turned on. There's constant 12 volt that runs the memory functions on the deck, and acc power that acts as an on switch to turn unit on when you turn the key, both wires need to be working to have the deck work. If it works off the car battery and not inside, and you try both constant 12v power and acc wire " with keys turned on " and neither work. Its your ground. You can extend the wire "with tape" and run it back to the negative terminal of the car battery, which I don't suggest. Or take and find a bolt/screw that's connected to all metal. The firewall would do if scrape the paint off to bare metal. The idea is that the metal is connected to metal. Some old units used to use the antenna as a ground. But I haven't done car stereo in a few years so idk. Hope it helps ya out, I've had stereos do crazy stuff in the past. But to get it to turn on, both wires red and yellow need 12v+ "one is the ignition, other is constant. And a ground. Get that worked out, then do speakers if there. Not already hooked up. Worst case , run a wire off the batt positive to the units yellow wire ,run a new ground ,and run a wire to the fuse box and find a fuse that runs only when the car is in acc on the ignition with key in, like wipers , something that doesn't turn on when the keys not in it.lights no good. Wrap a wire around a fuse that u choose and connect it to the red wire, the fusebox acts as the acc wire does to turn on the unit. Its a last case deal, if nothing else works. Any questions hit me up, sorry for the long message .

 

Hey guys. I got to the route of the problem. Yes as you suggested it waa an earthing problem. Thanks for all the feedback and apologies for my delayed response.

 

Glad you got it figured out!!