El Camino Central Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
105 Posts
Discussion Starter #1
My 74 Alt light (Dummy light) is connected to the heater fuse. It has something to do with the HEI system.
It says that this has to be connected. I want to install a volt meter in place of the ALT light.
So where would this wire go? Would I just leave the light hiding behind the dash? :dontknow:

I've considered going to the Chevy dealer and bugging a mechanic about this. This one really mixes me up. Why? What for? It "has" to be there?

Thanks so much!
 

·
Registered
Joined
·
2,205 Posts
Was that the orig wiring? The HEI should be on it's own thing. A wire from the ign switch to the dist when it is on. I don't think it goes through the fuseblock. I was not aware the alt light went through the heater fuse either. I thought the guages had their own fuse. I am not sure how to connect the voltmeter to the alt light. The instructions with the voltmeter may be able to tell you.
 

·
Registered
Joined
·
400 Posts
My 74 Alt light (Dummy light) is connected to the heater fuse. It has something to do with the HEI system.
It says that this has to be connected. I want to install a volt meter in place of the ALT light.
So where would this wire go? Would I just leave the light hiding behind the dash? :dontknow:

I've considered going to the Chevy dealer and bugging a mechanic about this. This one really mixes me up. Why? What for? It "has" to be there?

Thanks so much!
I think I understand what you have so I will give a try responding. Your 1974 El Camino's wiring diagram is listed on our site (two pages) at the following locations:

https://www.elcaminocentral.com/d2/articles/wiring/741.gif
https://www.elcaminocentral.com/d2/articles/wiring/742.gif

These diagrams show that the ignition switch provides power to three separate fuses in your fuse box as follows (along with amperage and color of wire):

i.) GAUGE PINK 10
ii.) WIPER BROWN 10
iii.) HEATER ORANGE 25
Please note, as designed by GM fuses "i" and "ii" share their power with two other fuses: DIRECT/BU and TCS SOL.

Normally you would expect the idiot lights to be provided with ignition switched power by the gauge fuse and its PINK wire. Apparently, at some point in your Elky's history, the source for the idiot lights' power has been modified to instead be coming from the HEATER fuse and its ORANGE wire (also ignition switched).

Voltmeters are generally wired as follows: i.) positive lead to power from ignition switch such as wires PINK, BROWN orD ORANGE discussed above; ii.) negative lead to chassis ground; and iii.) lighting lead to dash light circuit. Mind you each brand of voltmeter is different but I think just about every brand is wired along these lines so that the voltmeter deactivates when you turn the key off. With this wiring setup you will measuring the voltage at the battery after the voltage has run from the battery to the starter through a fusible link to the ignition switch to fuse box supply and out the fuse box.

This long and tortured path for voltage to the voltmeter means that the battery voltage that you may be reading at the voltmeter may be 2/10 or maybe as much as 1/2 volt lower than the battery itself. Measure the voltage at the battery and at your desired pickup point in the EC and determine the difference in voltage in order to make sure that your new voltmeter will give you accurate and meaningful information.
 

·
Registered
Joined
·
105 Posts
Discussion Starter #4
I don't know what got my mind set on that the tach wiring went through the alternator light.
I have 233 megabytes of diagrams, pictures and repair info on my computer. Somewhere I got the Alt and Tech cross wired in my head. It had something to do with that resistor wire coming off of the distributor.

I did find out that I need to be real careful of what tachometer I install. The HEI system that I have is real picky about this.

Thanks for clearing the cob webs out for me! :You_Rock:
 
1 - 5 of 5 Posts
Top