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73-87 Chevy _ GMC Trucks => Interior & Equipment => Instrumentation => Topic started by: fiddler on October 10, 2021, 09:43:15 pm
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I have a 1974 chevy c10 stepside. So when I turn on the ignition and start the truck I get all of the red warning lights on the dash coming on for a few seconds. I always thought this was to test the warning lights. So... now that they are not coming on... I don't know what is supposed to turn them on when I start the truck. Anybody got a clue?? Thanks for any help.
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The ignition switch has two dedicated terminals that ground through the ignition switch frame in the crank position. One terminal ties into the temperature warning lamp switch circuit and the other ties into the brake warning lamp circuit. After verifying that the cluster bulbs are, in fact, good and the Cluster Feed fuse in the fuse box is intact and passing current, use a test light clipped to B+ and probe the two GND terminals on the ignition switch to verify that each terminal actually grounds in the crank position. Repair accordingly.
The charge indicator lamp is controlled by the IC regulator internal to the alternator. Anytime the ignition is switched on with the engine not running the charge indicator lamp in the cluster will ground through the regulator via the dark brown wire connected to the #1 regulator terminal and illuminate. Again, using a test light clipped to ground and the ignition switched on with the engine not running, unplug the regulator connector and probe the brown wire connected to the #1 regulator terminal. If the test light illuminates dimly, the dash bulb should also be illuminated and its wiring from power through the bulb out to the alternator is intact and functioning. With the regulator connector still unplugged, probe the #1 regulator pin. If the test light illuminates normally, the regulator charge indicator circuit is functioning as it should.
The low oil pressure indicator lamp does not have a dedicated test function. Rather, it should illuminate anytime the ignition is switched on with the engine not running.
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thank you, now off on an adventure!!!
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Also remember that the electrical part of the ignition switch is mounted down low on the column, and there is a rod connecting it to a toothed rack on the ignition key switch.
If the rack breaks (cheap pot metal) or the rod/switch gets out of adjustment, the key switch may not move the electrical switch precisely, and it will not make all the right connections. You can usually troubleshoot by moving the key full travel back and forth to see if there is a point where dash lights come on correctly.