troubleshoot stock wiring harness

oderus1671 · 01-06-2013, 02:09 PM

I have a 2003 blaupunkt HU that has no memory, as stated in another thread, but noone seems to respond. So, I need to take the bull by the horns and troubleshoot it alone.

I have a feeling there is either a dead +12v circuit going to the HU, or the HU is shot. I think this because #31 fuse is not blown, but it retains no memory. How do I use a multimeter to check the harness? I would like to verify that theres power coming into the HU before going further. Also, should I be checking the fuse panel circuit as well? Not sure how to do this...Im not very electrically saavy, but I have a grasp on the basic principles. So, is there a guide on how to troubleshoot these wiring harnesses? Thanks in advance!

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Joseph Baker · 01-06-2013, 02:40 PM

well idk what the HU is but to check a circuit you need to put your meter leads in the right spots, black in the common/ground and your red in the votls ohms. then you set your meter to volts dc (direct current). now what you have to do is check the circuit in chunccks checking to see if there is power. so you put your red in on the first part of the circuit after the fuse and put the black on a kgg ((known good ground) any clean open steal connected to the frame or chassis or the frame/chassis. an open bolt screwed to the body or the best if possible reach the battery negative). now you check all the chuncks and when you dont have power is where your problem is and by doing that you find the problem by process of elimination but remember this most electronics on a vehicle have a 5 volts reference and the rest of the vehicle is 12-13 volts except the alternator which is much higher

oderus1671 · 01-06-2013, 03:16 PM

so, to check the +12 wire from the panel (fuse 31) to the radio, do I put the + lead on the +12v harness pin and the - lead on the harness ground pin? Im thinking I should be able to do a continuity test from the fuse to the harness, just to be sure that the wire is indeed connected. any thoughts? thanks JB for the response!

Joseph Baker · 01-06-2013, 04:33 PM

ya but you would still want to do those voltage drops to pin point the problem if the problem is in the wiring and not internal

oderus1671 · 01-09-2013, 04:24 PM

how would I go about checking the fuse block that my radio gets 12v constant power (Fuse 31)? I suspect that there may be no power to that fuse on the panel.