Expert: Peter G. Lee - 8/10/2006

Question
1990 Ford Ranger Pick-Up Truck Stock Radio.

I sent this problem to you yesterday however it might not have gone through because of problems with my email.

I had a after market radio/cd player in the above truck however it broke.  I decided to put the stock Ford radio back in my truck.  When I plugged the old radio in to the plugs it would not work.  The cassette player plays howeverf the radio will not work.  I comes on howver I can only hear static.  None of the controls work like the tuner, seek, or bass and trebel.  I hope that you can help me with this problem.  I think it in the wiring.  Thanks in advance.  Ron.


Answer
I think you are right and a complete check of the vehicles wiring is in order, I am pasting a standard text for test and diagnose but you can ignore the speaker bit I think.

Basic test and diagnostic procedure for car wiring harness.

You will need the following;

A test meter set at 20vdc or a test lamp( two wires on a 12v bulb) or probe (like a screwdriver with a 12v bulb in it and a lead and clip)
Some masking or paper tape to label wires and a marker pen,
An “AA” or “AAA” torch battery, (or borrow one out of the TV remote for an hour)

First the easy stuff, the speakers, (without amp!)

Speaker wires.
These are normally twisted together in pairs if you are lucky and are the same colour for each pair but one with a colour trace on, i.e. blue and blue/white, green and green/white. Touch a pair across the battery and you will hear a noise on the corresponding speaker, label it (e.g. left rear), continue until all four are identified and labelled.

Power leads connector.
Earth one side of your meter or tester to a metal part of the car, probe each wire until you have a wire that is live all the time with the ignition OFF, label this ‘+30’.
Switch on ignition and redo test until you find another previously dead wire now live, this is ‘+15’.
Switch off ignition and switch on the side / park lights, repeat test until you find a third live, label this ‘lights’. Switch off the lights.
You should now have two or three left. One will be earth, (usually black or brown); one could be to an amp and or electric ariel (usually blue or blue white) and one for phone mute if fitted. Clip tester to +30 and probe one of the remaining wires, if you have an electric ariel it will go up. Connect your DIN plug to the correct wires and jobs a good un’.

If you have them the ISO DIN connections are.

Speakers

Right rear -,  right front -,   left front -,  left rear-,
Right rear +, Right front +, left front +, left rear +

Power block viewed from cable side

Phone mute (white),/   n/c, /      ariel & amp (blue), /ignition (red)

N/c, / 12vlive, (yellow or orange), / lights, (various colours),/ negative (black)

Hope that helps, Peter