wiring questions for this noob

[c20pickup]

just like the title says.. im a wiring noob, soooo, layman's terms please
just a few questions im sure easily answered by some that are better at this wiring thing than me!

starting from the top, my truck is a 1970 c20, non A/c, 350, hei, passenger side one wire alt., 700r4, new dash cluster with tach, and volt guages, i purchased all new stock style wiring harness for the engine, cab, headlight, taillights and under dash from classic heartbeat. the harness was modified to work with the hei and the internally regulated alternator.

my questions are as follows.

1. how do i wire the alternator, i understand my alternator is one wire, but it also has a rubber plug where the two prong plug in would normally go. the new harness has the thick red cable for the lug on the alt. but also has the two wire plug in, is it detrimental to have the two prong connector plugged into the alt. i thought i remember reading somewhere it doesn't matter either way if its plugged in or not and the two wire plug is just for the gauge ad idiot light in the dash.

2. when wiring the starter and battery i should only need one thick cable going to the lug on the starter, and another cable from the alternator to that same lug on the starter, or should i be running the alt. cable right to the battery instead?

3. another starter question. the stock style harness has two wires for the starter, a purple and a yellow. the truck has a high torque mini starter, so my understanding is that the yellow wire isn't used and i should only use the purple wire as the trigger to the starter and the yellow just gets tied up and isnt used at all.

4. in the headlight section the glass fuses that belong to each headlight, what size fuse needs to be used in there, i cant seem to remove any from my old harness without shattering them.

5. grounding. where are all the ground cables located? engine to frame, engine to body, body to frame, bed to frame???, am i missing any? also, where does the battery get grounded to? ive seen some grounded to the frame rail and on other cars ive seen them grounded back to the alternator bracket (seems kind of hokey to me).

im sure i will have more as i continue working on the wiring, thanks in advance!

[Wrenchbender Ret]

#1. You don't need the 2 smaller wires. You could remove the rubber plug & stick the connecter in to look authentic. There probably is no terminals Under the rubber plug.
#2 You can hook it either way but its best to use a terminal block.
#3 The yellow wire is not used with HEI.
#4 The stock system does not use fuses for the head lights. There are fuses for the tail & stop lights & dash lights.
#5 Hook the ground cable to the alt bracket. Hook a 8-10 gauge ground wire from the engine to the frame. Run another 10 gauge from the frame to the core support.
I hope this helps. If any one else has something to add or correct jump in.
George

[demian5]

Originally Posted by Wrenchbender Ret

#5 Hook the ground cable to the alt bracket. Hook a 8-10 gauge ground wire from the engine to the frame. Run another 10 gauge from the frame to the core support.

Be sure you connect a ground wire between the battery and the fender.
And a ground wire between the cab and the engine.

[c20pickup]

Originally Posted by Wrenchbender Ret

#1. You don't need the 2 smaller wires. You could remove the rubber plug & stick the connecter in to look authentic. There probably is no terminals Under the rubber plug.
#2 You can hook it either way but its best to use a terminal block.
#3 The yellow wire is not used with HEI.
#4 The stock system does not use fuses for the head lights. There are fuses for the tail & stop lights & dash lights.
#5 Hook the ground cable to the alt bracket. Hook a 8-10 gauge ground wire from the engine to the frame. Run another 10 gauge from the frame to the core support.
I hope this helps. If any one else has something to add or correct jump in.
George

my alternator has the two prongs under the rubber plug and the connector goes in just fine, i was just wondering if it would harm anything and how my guages and idiot lights would work in the dash if i didnt run the two wire connector.

what are the little rubber plugs for on the headlight harness then, are they not used? there is one on each side, if you were to open them up they appear to accept a glass tube style fuse, when i go to my original harness the rubber is so dried out im not able to open them without shattering the glass.

as an update for the alternator wiring, i ran a cable to the starter from the alternator today, and got the truck to fire up and run, only to find out the harness has a built in wire for the alternator to the battery (it runs up along the core support) so finding that was pretty handy. and it eliminates the cable i did have going to the starter.

thanks for all the help!

[demian5]

Originally Posted by c20pickup

what are the little rubber plugs for on the headlight harness then, are they not used? there is one on each side, if you were to open them up they appear to accept a glass tube style fuse, when i go to my original harness the rubber is so dried out im not able to open them without shattering the glass.

Odd, Tiny, lame, fragile 3A (?) fuses for the amp meter in the dash.

[VetteVet]

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Originally Posted by c20pickup

just like the title says.. im a wiring noob, soooo, layman's terms please
just a few questions im sure easily answered by some that are better at this wiring thing than me!

starting from the top, my truck is a 1970 c20, non A/c, 350, hei, passenger side one wire alt., 700r4, new dash cluster with tach, and volt guages, i purchased all new stock style wiring harness for the engine, cab, headlight, taillights and under dash from classic heartbeat. the harness was modified to work with the hei and the internally regulated alternator.



my questions are as follows.

1. how do i wire the alternator, i understand my alternator is one wire, but it also has a rubber plug where the two prong plug in would normally go. the new harness has the thick red cable for the lug on the alt. but also has the two wire plug in, is it detrimental to have the two prong connector plugged into the alt. i thought i remember reading somewhere it doesn't matter either way if its plugged in or not and the two wire plug is just for the gauge ad idiot light in the dash.

In addition to what wrenchbender said.
You should use the two small wires in the plug. Some of the later one-wire alternators can use both. The small wires are probably wired correctly in the harness that you bought. The brown wire That goes to the no.1 terminal on the alternator would avoid having having to rev the engine to start the alternator charging as it excites the alternator fields immediately as soon as the key is turned on. The other wire ( usually red or blue) that goes to the no.2 terminal, provides remote voltage sensing to the internal regulator, to compensate for voltage drop downstream from the output terminal on the alternator.

2. when wiring the starter and battery i should only need one thick cable going to the lug on the starter, and another cable from the alternator to that same lug on the starter, or should i be running the alt. cable right to the battery instead?

What difference does it make if you wire it to the big cable on the starter or to the big cable on the battery it's the same place electrically.
What you should do is run the alternator output wire to the main junction, where the wire from the battery feed and the truck circuit loads meet. This will let the battery power the truck if the alternator quits working, and it will also allow the alternator to charge the battery, and power the truck loads which is how it is designed to do. It would be smart to upgrade the output wire to 10 gauge or better yet 8 gauge to handle higher amp loads.

3. another starter question. the stock style harness has two wires for the starter, a purple and a yellow. the truck has a high torque mini starter, so my understanding is that the yellow wire isn't used and i should only use the purple wire as the trigger to the starter and the yellow just gets tied up and isnt used at all.

4. in the headlight section the glass fuses that belong to each headlight, what size fuse needs to be used in there, i cant seem to remove any from my old harness without shattering them.

The headlights have no fuses. You may be looking at the ammeter fuses (4amps) that protect the battery gauge(ammeter). They're in two small wires 18 gauge that go to the dash cluster plug to pins 1 and 12 if you have the gauge cluster. If you have the charging light there won't be any small wires or fuses. Here's a diagram with the ammeter wiring and the alternator wiring shown.



5. grounding. where are all the ground cables located? engine to frame, engine to body, body to frame, bed to frame???, am i missing any? also, where does the battery get grounded to? ive seen some grounded to the frame rail and on other cars ive seen them grounded back to the alternator bracket (seems kind of hokey to me).

im sure i will have more as i continue working on the wiring, thanks in advance!

[c20pickup]

Originally Posted by VetteVet

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thanskfor all the great help!!