Electrical Issues:  Main Power Feeds


There is a problem with a power feed in the electrical system.  There are several levels of power feeds and this page will help you track down the problem.


To diagnose a power feed problem, use the list below to narrow down the source of the problem:

If you do not see your exact symptoms here, try the closest one.  In order to do ANY of these tests, you really need to have at least a DC voltmeter.  A multimeter that can measure DC voltage, current, and resistance is much more useful.  If you don't have a multimeter and plan on doing anything automotive, go and get one right now.  You can get a cheap analog multimeter (or "multitester") for $10, but I recommend getting a digital one because they are much easier to read quickly and many are auto-ranging (you don't have to select the range and worry about blowing it up).  You can get those for around $10 to $20.  If you are serious, you can spend $40 - $100 on a good, digital multimeter than can measure high currents with fuse protection, etc.

No Power At All

Use this section if your vehicle has no power at all.  This means that the always-on accessories, such as headlights and the interior dome light, do not work.  When the key is turned to the "accessories" position, no other accessories (radio, fan, etc) have power.  When the key is turned to the "on" position, the instrument panel does not come on (power loss/check engine and oil lamps).  When the key is turned to the "start" position, nothing happens.

The most common source of this problem is battery-related.  Follow this procedure to track down the problem:

If you made any of the above repairs, but are still having electrical problems, go back to the Diagnosis section to find the next problem.

No Ignition Feed

Use this section if the instrument panel (lights, chimes, etc) does not come on when the ignition is turned to the "on" position.  The engine does not crank when the key is turned to the "start" position.  However, the accessories (headlights, radio, etc) have power.

This condition is almost always a blown fusible link.  The main power to most of the engine's systems comes from the J2 splice.  The J2 splice is powered through the ignition switch from the J1 feed.  As you can see by the diagram below, the J1 feed comes right from the battery, through a fusible link.  The diagram shows hypalon wire fusible links, but your vehicle may have a power distribution and relay box near the battery.  Inside are the removable fusible links and a diagram describing them.

The hypalon wire fusible links look just like regular wires.  The easiest way to test them is to tug on them.  A blown link will stretch like a rubber band.  Other fusible links usually have a window on them, showing the link itself.  If it looks blown, replace it.  Hypalon links have to be spliced back together.  If there is enough wire left to splice, a butt crimp-connector works well.  Otherwise, you will have to add some wire and somehow splice it back in.  If all fusible links seem to be intact, then there is probably a wiring problem between the A1 distribution and the ignition switch or the switch itself may be bad.  You will need to consult the wiring diagrams for your vehicle to aid in tracking down the problem.

Starter Problems

Use this section if the engine does not crank when the ignition key is turned to the "start" position.  However, the accessories (headlights, radio, etc) and instrument panel (lights, chimes, etc) have power.  This condition has two possibilities that are the most common.  You can narrow it down somewhat this way:

The starter relay is usually located on the left strut tower, or inside the power distribution and relay box.  It is usually wired as shown in the diagram below, which is based off of the 1987 wiring.  If you have relay box, use you wiring diagrams to determine which pins do what.  Use the following procedure to located the problem:

No Engine Feed

Use this section if the engine cranks when the ignition key is turned to the "start" position, but there is no spark, fuel, etc.  Also, the accessories and instrument panel work.  This problem can have several causes and may take some time to track down.

Basically, most of the engine's components that require 12V get it through the J2 or Z1 feeds.  The Z1 feed is basically the J2 feed switched on and off by the ASD Relay.  On 1987 and earlier models, the ASD relay was located inside the power module.  For later models, it was a black plastic relay located externally, near the other relays.  The ASD Relay is controlled by the computer and is turned on when the computer detects a signal from the ignition reference sensor.

The J2 feed supplies power to all of the solenoids, some relays, the alternator field, oxygen sensor, diagnostic connector, etc.  It almost always is a dark blue 14 gauge wire.  If you do not see a dark blue wire, look for a common wire color on all of the solenoids.  This should be your J2.

Now you need to check the Z1 feed.  The Z1 feed supplies power to the ignition coil, fuel pump and fuel injectors.  If you have a 1987 or earlier vehicle, the Z1 feed comes right out of the power module (the ASD relay is inside).  On later models, the Z1 feed comes from the ASD Relay.

No Radiator Fan Feed


No Rear Window Defroster Feed


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Updated 01/04/2005.

Copyright © 1996-2005 Russ W. Knize.