Electrical question

[nightrider50]

Driving home on the freeway last night and all of a sudden my instrument panel lights went out. Tested fuse #4 and fuse #13 today... Both are good. Did some more testing and:

What doesn't work: parking lights (the ones on each side of head lights), instrument panel lights, tail lights

What does work: head lights, fog lights, turn signals, brake lights, hi beams, dome light (turned on with dimmer)

Any ideas or suggestions on what it could be or what I should check?

Thanks!

 

[Blown88GT]

Test Main Light Switch after unplugging it.

 

[nightrider50]

Alright I am a beginner with an ohm meter. I turned the dial to "20k" and removed the main light switch. Assuming a 1.00 reading means open circuit and 0.00 reading means closed circuit... The 1st, 2nd, 4th, and 5th tests on this diagram all checked out ok. Does this mean the switch is fine? What would you check next?

 

[Blown88GT]

Alright I am a beginner with an ohm meter. I turned the dial to "20k" and removed the main light switch. Assuming a 1.00 reading means open circuit and 0.00 reading means closed circuit... The 1st, 2nd, 4th, and 5th tests on this diagram all checked out ok. Does this mean the switch is fine? What would you check next?

Bad ground in engine compartment.
1988 EVTM

 

[jrichker]

Automotive electrical troubleshooting 101.​

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Automotive circuits are mostly simple stuff: a power source, a connection path, a control device, a load, and a ground.
The battery/alternator is the positive power source.
The wire and fuses are the connection path.
Control devices are switches, relays and sensors.
A load is a light, motor, solenoid or heater element.
In automotive circuits, grounds are the return path so the electrical power can flow from the load to the negative side of the power source.
Electricity flows like water:
Voltage is like pressure,
Current in amps is like volume,
Resistance is like the kink you put in a garden hose to decrease the pressure or volume.
Power is pressure multiplied by volume or voltage multiplied by current (amps)

Digest that, and you just got the first 3 days of Electricity 101.

Use some jumper wires (connection path and ground) to hook up a switch (control device), a battery (power source), a light bulb (load). Now make the light turn on and off with the switch.

That's the electrical lab for the first week of Electricity 101.


For free automotive electrical training, see Automotive Training and Resource Site . I have personally reviewed the material and it is very good. If you are new to automotive electrical troubleshooting, I highly recommend you spend a hour or so going through the material. You'll save at least that much time troubleshooting problems.


Practical steps on how to use a DVM or Multimeter:
Step 1.) Find the instruction book that came with your Multimeter. Read it and familiarize yourself with how it works and how use it. If you lost the book or didn’t get one with it, do a Google search on the web to find the manufacturer’s web site & download a copy of the manual.

Step 2. ) Make sure that you know what test lead plugs into which jacks on the Multimeter. There are usually several different jacks on most Multimeter's, and they have different functions. Make sure that your battery(s) in the Multimeter are good: if you have any doubts, replace the battery(s).

Step 3.) Once you are sure that the Multimeter is functional and you have the leads plugged into the jacks for Ohms ( the upside down “U” symbol), do some simple measurements to make sure that you know how to use it correctly. Set the switch to the lowest range and touch the leads together: you should not see “nothing” but you should see 1.0-0.3 ohms. Measure a 60 watt light bulb: cold it will measure about 17.5 Ohms. It you measure it while it is hot, the reading will be greater.

Step 4.) Make several test measurements using the ohms function and the DC volts function. Remember all resistance measurements must be done with the power off the circuit. This avoids false readings and possible damage to the ohmmeter.. Repeat steps 3 & 4 until you are sure that you can do it without making any mistakes.

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[nightrider50]

Where is that ground located? If the switch turns on the head lights and fog lights, wouldn't this mean the ground is good?