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Hi All,
Can someone help me decipher my fuse block? I’m looking to add some gauges (oil and temp) as well as a tach later. For a keyed source for lighting of those gauges, I’d like to run a wire to the fuse block like I did to my IGN terminal for my MSD. Looks like I’m missing a couple of terminals in some spots but I have one above the IGN and BAT terminals, looks like it’s labeled ACCSY. Is that a source I could use for the lighting of the tach and /or gauges?
Reposting the pic of my fuse block as it looks like it didn't take in my original post. Hopefully someone can confirm that the ACCSY spade is one that I can use for the lights on my aftermarket gauges.
I tapped the tach and under dash gauge lights into an existing dash light wire so they would dim/bright along with the other dash lighting. That ACCY terminal will provide constant 12 Volts and you won't be able to control the intensity as you can with the other dash lights.
The BATT terminal is hot all the time.
The IGN terminal is hot with the key in RUN.
The ACCY terminal is hot with the key in either RUN or ACC.
More to the point, you want the gauge lights to be connected to the instrument panel lighting feed. This is a grey wire in the dash harness. There should already be a plug for the clock illumination feed behind the dash. Plug into that and your gauge lights will come on and off (and dim) with the dash lights.
Can someone tell me which fuse in the fuse panel is for the gauge lights (when headlights are on). All three gauges do not light up (Tic-Toc-Tach, Speedometer, ect). All three function properly including the dummy lights (GEN, BRAKE...).
Can someone tell me which fuse in the fuse panel is for the gauge lights (when headlights are on). All three gauges do not light up (Tic-Toc-Tach, Speedometer, ect). All three function properly including the dummy lights (GEN, BRAKE...).
Thank you.
The 4A fuse labeled INST LPS (as in Instrument Lamps). Keep in mind that the illumination circuit in the gauges is completely unrelated to the idiot lights or any other gauge functions, except for the common ground strap. Also note that the instrument lamps are controlled by the dimmer rheostat in the headlight switch. The **** is turned all the way counterclockwise, right?
"Also note that the instrument lamps are controlled by the dimmer rheostat in the headlight switch. The **** is turned all the way counterclockwise, right?"
Yes the **** is turned all the way - I checked both directions. I am wondering if the dimmer rheostat is bad, but there is no way of checking that.
"Also note that the instrument lamps are controlled by the dimmer rheostat in the headlight switch. The **** is turned all the way counterclockwise, right?"
Yes the **** is turned all the way - I checked both directions. I am wondering if the dimmer rheostat is bad, but there is no way of checking that.
Thanks,
Bill
The 4A fuse is fed from the rheostat. Use a test light or VOM to check for voltage at the fuse. You should be able to see the voltage rise and fall as you turn the **** (with the headlight switch pulled out, of course). Yes, it is possible for the rheostat to go bad. If you do get voltage, the switch is fine.
Well I tested the fuse link with a test light and it was dead 75% of time turning left to right and right to left multiple times. So it seems the switch is bad after 51 years.
So I ask the question, anyone have the procedures for removing and installing a new switch. I am sure being GM, it will require going under the dash which is a SOB.
Headlamp SW removal is contained in Section 12AA of the CSM - Instrument Panel. The 1970 model year Headlamp SW is identical to the 1971 model year Headlamp SW as are all part numbers associated with the Headlamp SW for both model years. Here are images and instructions from the 1971 CSM.
