2003 GT - Dash lights not working after stereo install

Discussion in 'SN95 4.6L Mustang Tech' started by Bughracing, Sep 7, 2009.

  1. I'm hoping some of you guys can help me. A month or so ago I installed a new CD player in my 2003 GT. I used a Metra 70-5519 wiring harness from Best Buy. I ended up running separate wiring to each speaker because the previous owner removed all of the amplifiers and the rear sound bar in the vehicle.

    Everything went smoothly, but I accidentally ran the illumination power and illumination ground wires together to the 12v power wire. I have no idea how I did this, but I did. I removed the illumination wires completely so they are not connected. Unfortunately in the process my dash lights no longer work. All of the seat belt, airbag, check engine, etc lights work, but the speedometer, tachometer, engine oil temp, water temp gauges do not have any back light anymore. The gauges themselves work fine, just no lights so I can't see them at night. I have already replaced the headlight switch thinking that I might have blown something internally, but it made no difference. I have checked all of the fuses numerous times and they are all fine. I double and triple checked my wiring, but everything is correct. I just pulled the gauge cluster out a few days ago and checked all of the bulbs, but they are all fine. I even swapped them around with known working bulbs and they are definitely all good.

    Can anyone give me any hints on what to check next? I don't care what I have to replace, I just need to get it done! I can't drive my Mustang at night and this is getting really old!

    Thanks for anyone's help!
  2. i know that you have already have checked the fuses but check them again use a test lite and a ohms resistance meter (fluke meter) to check resistance threw the fuses. i had a similar problem before in my truck i blew a fuse and it blew right on the very edge of the prong that goes into the fuse panel and check and make sure you didnt forget to put a fuse back in because i did that and it caused the fuel pump to shut off and i had the truck torn completely down cuz of a missing fuse. hopefully you wont tear yours down like i did and it be simple like that. hope thats helpfull
  3. Thanks for the tip. I've probably checked the fuses 2-3 times already now with a fuse light and pulled them out one by one, but I'll try it again with a multimeter. Any other suggestions?

  4. Per the wiring diagram, fuse 2.37(5a) controls a bunch of stuff including the rear window defroster. If the fuse was blown, a lot more than just the insturment cluster lights would not work.

    My vote is the ground from the cluster is no good. We can test for this by checking for 12 volts at the cluster light socket and a known good ground. If you get 12 volts, then turn everything off. Take an ohm reading from the other light bulb terminal to a known good ground. If the reading is high (open), then you will have the answer.

    Then it is a matter of finding exactly where the stereo install messed up the ground. It is also possible that the ground wire was overload and burned up. This could be the case if your stereo uses a lot of power and you tried to "double up" on the grounds.

    One more thing, check for the possibility that you burned up a foil trace on the printed circuit board inside the cluster. Look for burn marks on the printed circuit board. IMO, this may be the most likely cause of your problem.

    The fix may involve a trip to the salavage yard.
  5. I'm starting to lean towards a bad cluster as well :(

    I just put them original Ford Mach stereo back in, eliminating any of the wiring changes I made, and it works, but the dash lights still do not work. I'll double check the fuses again, then check the wiring... then try to find a cheap used cluster.

    If anyone has any other suggestions, I'm all ears!

  6. I didn't read everyone's replies so if someone already said this, I apologize... I know you said you checked the fuses, but did you check both sets of fuses? There is also a fuse box in the engine bay that has two fuses that control the radio system. One to the radio and one to the amps. By your description, you shorted power to ground. A fuse will blow when you do that...

    On Edit: ...and, the fuse is there to protect your wiring and your cluster devices...
  7. Thanks for the tip... Well, I tested all of the fuses again with a multimeter and they all ohm'ed out just fine. I then did something that I had not done before and started the car with the lights on, thinking that maybe something would show different under load. Well, everything under the dash was the same, but two of the large fuses under the hood were different. One of the large 20a fuses didn't tone out at all and one of the 30a fuses showed 84 ohms. I bought two new fuses at NAPA and swapped them out. To my amazement... nothing changed... no dash lights :(

    Please, any other suggestions? I'm currently looking for a replacement dash cluster, but it's going to irritate the hell out of me if I blow $100 or so for a replacement cluster and it still not work. I'm looking for one though...

    Any other tips would be GREATLY APPRECIATED!

  8. Do you know how to read schematics? Can you get them? If not, I probably can. Don't start buying things till you know for sure what it is. 2003 GT right? I'll see what I can find tomorrow if I get a chance to pull your wiring diagrams.

    If it were me, the first thing I would do is wire back up the original set up without the stereo to see if it works again. Then I would re do your install one step at a time till I see the problem again. But, I'll bet the original set up doesn't work anymore and it is a fuse, relay or fusible link somewhere...
  9. Yes, I can read schematics, but no I do not have any for the wiring or know where to get them. If you have access to them I would really appreciate it!

    I actually did put it all back to stock with the factory CD player, but it made no difference. The radio still worked fine, but no dimmer and the dash lights did not come back.

    On a side note, my wife and I just took the Mustang out to get ice cream and I realized that the A/C backlights are out too. So... I guess the extent of the problem is bigger than I first though. I still can't see this being anything other than a fuse, but unless there is another hidden fuse box that I'm missing because all of the ones under the dash and under the hood are good.

  10. Well I found a picture last night of the under hood and under dash fuse boxes with what each fuse goes to. I'm going to just swap out all of the fuses that have anything to do with the dash and see what happens next.

  11. As a reminder, there is an instrument dimmer on the head light switch. Without hurting anyone’s feelings, has someone checked to be sure it is not turned all the down?

    Per the wiring diagram, the following illumination circuits are all on the same fuse F2.37 (5 amp) in the Central Junction Box (CJB).

    Function selector Switch
    Rear Window Defroster
    Instrument Cluster
    Transmission Control Switch
    Fog light switch
    Traction control Switch

    If ALL of the above are not working, then the list of things have in common is very short. Namely they are the Fuse F2.37, 20 Ohm dimmer resister, and the wiring harness.

    If ANY of the above items ARE working, then it can not be the fuse. Nor can it be the dimmer resister.

    I am assuming that you have not removed the cluster possible because it is a lot of work. Here is an option. Remove fuse F2.37 from CJB. Turn on the parking lights. Measure the voltage between both of the fuse connectors and a known good ground. If you find one with say over 10 volts, this proves the dimmer resistor is good. If not, you will need to focus your efforts backwards towards the dimmer switch.

    There is also a pinpoint test in the Ford service manual. It basically proves voltage/ground to/from the instrument cluster connector. Voltage should be on cluster connector C220b pin 4. The ground on pin 1.

    OBTW, if you attempt to ring out a live circuit with an Ohm meter, you will get erroneous results because there is current flowing. For an Ohm meter to work properly, the circuit must be inactive (dead).
  12. You definitely aren't hurting anyone's feelings here! But yes, I have checked that numerous times. I even replaced the switch, but it made no difference.

    Unfortunately for the F2.37 you mentioned, the rear window defroster, fog light switch, traction control switch, and radio all work, so I doubt it's that.

    As far as the cluster, I've removed it numerous times. It only takes 5 minutes or so. I checked all of the bulbs as well as moving known good working bulbs into the "non working" spots, but it didn't help.

    Thanks for the tip about the ohm meter! I am planning on still swapping all of the fuses that tie back in any way to the radio, A/C gauges, or instrument cluster, but have been sick all day. Hopefully tomorrow I will be able to do that!

  13. I know what you are saying but to be more clear, the circuit must be inactive... Meaning, no power applied.
  14. Fuse F2.37 controls the illumination for the mentioned items (not the function themselves). Your post stated there were other lights not working. Which lights work and which don't? This makes a difference in tracking down the most logical place to look.

    If all of the illumination devices on the same fuse DO NOT work, then look at the fuse, dimmer resistor, or the wiring harness.

    If just the cluster lights do not work, the look at the power wiring to the cluster or the ground. I was not asking to have the bulb itself checked. Instesd asking for a voltage test in the socket. This was to help narrow down if a power problem or a ground problem.

    If some of the bulbs in the cluster work and others do not, then let's focus attention towards a burned PC foil tracing inside the cluster.

    The exact symptions do help.
  15. Thanks guys for all of your help! Sorry for taking so long to reply but I finally found the problem. I again tested ALL of the fuses with no power and they all checked out fine. I checked each one to make sure it was the proper fuse and it was in the right place, and they all were. I pulled the instrument cluster again and tested the leads and it appears to be grounded fine. I was just to the point of buying a new cluster to see if that helped. I decided to do what I said I would try earlier and pull each fuse... again... but this time just swap each with a new fuse. I did this row by row with the fuses in the engine compartment, checking the dash lights after each row... no luck. I then did this again with this interior fuse box and when I got to the last row IT WORKED! The fuse that was bad was the 5a that goes in the #37 slot for Adjustable Illumination... which would make sense. Now the dash lights work fine.

    The funny thing is I put the bad fuse back in and it ohms out fine and the test light works on it?!?!?!? :shrug:

    I wish I had known that's all it was and it would have saved hours of trial and error. The only thing I can think of is that the crack in the fuse is incredibly small and maybe when it was pushed into the fuse box, the leads made it touch sometimes? I really don't know... Can anyone make a guess as to why it would appear to be just fine in the fuse box, but when you take it out, it sometimes appears to be good, sometimes bad?

    Thanks a million!
  16. Electricity is weird. :shrug: That's all I've got :)
  17. Testing electrical circuits

    How did you perform the Ohm test (between which two points)? An Ohm tester runs a small current through the ciircuit. If the circuit is active (not dead), then the test will be inaccurate.

    Best to Ohm test a fuse out of the car.

    How did you perform the voltage test at the fuse? If for example, you were testing being a known good ground and a terminal of the fuse, even a blown fuse have voltage on one side. A good fuse will have voltage on both.

    My son and I had an experience with a blown fuse. We visually checked every fuse. It was only after it was pulled and examined closely could you see that it was blown. Lots of wasted time chasing wild geese.

    Hope my information was helpful.
  18. I was testing it, for the most part, using the two leads on fuse while it was still plugged into the fuse block. From now on if I suspect a fuse is bad, I will just start with pulling and testing each fuse!

    Thanks for all of your advice!
  19. You have to isolate the fuse from the circuit to read it for resistance, otherwise it will read through the rest of the circuit. Thats probably why you had 84 ohms when you read the one.
  20. LOL, i did this exact thing today on my Xterra while installing an in dash nav.

    i ended up having to ground the - illum wire to get my dash lights back working. i think i burned out the dimmer switch somehow, so i just bypassed it and everything works great again. the dash is just on full bright all the time, but thats how i keep it anyway