dembo

Heya,
I'm currently installing the electric fan & would also like to wire up the electric choke.
I've read alot of posts where people get the switched 12V from the fusebox. But ..
On the interior side the IGN lug is taken by a dedicated wire to the HEI as read in alot of posts.
The ACC lug is taken by the electric tach (75 in my 74) and the supply to the brake switch for the transmission lockup) (std brake switch switched with a cruise control brake switch).

To supply the radio I'm using the yellow wire from the dash harness intended to go to the radio. (I hope this is actual keyd 12V? as its a yellow wire)

So I still need 2x keyed 12V for the electric fan relay & the choke.
I've read posts not advising to use the wiper motor wiper, but not real explanation why not to. I suppose the draw from the fan relay & choke are minimal?
Or would you suggest to wire them into the tach/lockup wire ?

Thanks for any tips,
Nick

68/70Vette

My solution may not be directly applicable since I had removed the speedo/tack panel prior to wanting to pick up a switch DC power line. I spliced into the line going to the ignition switch (it was a large gauge wire and used a mini-butane torch to solder my pick up wire to it. I ran the wire through a fuse (bought from lectric limited I think) and then went to a master distribution terminal for routing to the fans, etc.

...Roger...

You probably need to get some relays and use the limited fuse box taps to key the relays.

dembo

Thanks Guys,

Damn this is the thing which is holding me back to put the interior & windshield back in Thought it would be less complicated.
I guess both of you are saying stay away from the wiper motor keyed 12V wire?

68/70Vette : It's still a option, the dash is out as well, just the steering column is in. What amp rating did you choose for the fuse? The fan itself gets its power from the alternator, so only for the elec choke & the fan relay the draw will not be that significant no?

Roger : would you wire extra relays into the system ? I've got the painless wiring harness for the fan, so the relay is included.

Could I get by with splicing both into the wire giving 12V to the dizzy from the IGN lug?

Sorry I'm more mechanically inclined then electrical and gotta figure it out all on my own.

Thanks,
Nick

...Roger...

I think you need to back up and rewire your 74 like a 75 , difference being the addition of the HEI. Your bandaiding to incorporate new electrical items into the 74 system.
The 12 pink coming from the ign switch is a powerful circuit and I think you need to utilize it , as it is now you have disconnected 1/2 of it and you are running your dizzy through the GAUGES 10 amp fuse.
The half you disconnected is the original resistor wire going to the old points ign coil.
IMO (and probably the easiest to do )you should go under the dash find the 12 pink (not pink / black) coming from the ign switch follow it to the back of the bulkhead and clip it there and use this to power your dizzy, this will free up the IGN spade but remember the spade is 10 amp limited. ( you can do this 100% right by eliminating the resistor wire and running the pink circuit through the bulkhead - harder to do)

You mentioned the wiper motor keyed wire , if you use this wire for a relay you will double click the relay . ( ON-START-ON )Not a big issue.A little ign switch 101. When you turn the key to ON the electrical system lights up but when you turn the key to START part of the system shuts back down until the key is returned to ON. This is your double click of the relay that doesn't have to be. You would also be running through the wiper fuse,if the wiper fuse blows whatever is on the circuit is dead.

The 12 PINK circuit is a powerful circuit,the 12 BROWN and 12 ORANGE circuits are also powerful,they all are fed by the 12 RED battery direct circuit BUT the PINK is hot when the Ign switch is in the ON "and" START positions , the BROWN and ORANGE are hot "only" in the ON position. Both the brown and orange will double click anything connected to them( if this is an issue).
Remember though these circuits go THROUGH the ign switch , using relays you can bypass the ign switch and go battery direct.

If the Brown wire circuit is your choice it is easily accessible just beside the ign switch at a radio capacitor, just unplug the cap and plug into the brown. ( T the cap in if you like )

Hope I haven't added to the confusion but IMO I think the way your going you might have problems with too many "add-ons".

7T1vette

All "12 v keyed power lines" are NOT created equal. The most important issues with electrical wiring are: 1) how much current does the accessory I'm adding require? and 2) how much current can the wire [I'm wanting to use] safely provide? If you just start hooking things up '*****-nilly', your next thread will be on the subject of electrical fires.

Listen carefully to what folks are trying to tell you here. It's important. Electric fan systems suck a LOT of current. Your best solution is to install a power relay system on an existing "keyed" circuit...so that turning on the relay doesn't absorb much power, but the relay can then send plenty of current to the fans via separate (properly sized) wiring being fed from the battery or alternator. Also, if you install new fans, you will likely need to upgrade your alternator so that it can actually supply the added current the fans will need.

dembo

That's great info! It's the reason why I'm asking advise, to avoid fires & bubba wiring. The painless elec fan wiring provides the right Ga wires right from the alternator over the relay to the fan. The alternator is a 105Amp CS130 model so that should do.
I've read a couple of threads on here where it was written that 12V from the acc lug to the dizzy is ok. But while it's all apart it's better to do it right.
Unfortunatly I don't have my wiring diagram here, so it'll have to wait till monday.
I think the double click is not what I should want for the relay and I also presume you need the 12V when the key is in the start position for the choke.
The yellow resistance wire coming from the starter to the original points distributor) has been taped up (also read this in a thread). So the pink wire is the one to search for. If you look at the dash wiring harness, inbetween the tach & speedo there is a seperation in the harness running down the steering column to the connectors. If I was to unwrap the tape in this part I should find the pink wire no?
That would be the easiest to splice it in here as it is closest to the firewall grommet.
But then again is it fused at this point?
In total I should have
1)keyed 12V for the radio : used the original radio connector yellow wire, 20A fused according to the owners manual so that should be sufficient as the power consuming bits of the radio are powered directly from the battery (as instructed by the installation manual)
2)keyed 12V for the electric tach, this is now on the acc lug 20A fuse on the fusepanel?
3)keyed 12V for the lockup harness, now together with the electric tach on the acc lug 20A on the fuse panel?
4)keyed 12V to power HEI dizzy, currently on the IGN lug = not ok
5)keyed 12V to power the electric choke : not connected
6)keyed 12V to the fan harness relay : not connected
7)keyed 12V as a spare for EZefi & electri fuel pump or alike in the not so near future.

The radio I will keep as it is, the lockup & 12V to tach I'll keep as it is, so I need 4xkeyed 12V for dizzy, choke, fan harness & spare.
Which I should get from the pink. I think these 4 need the 12V in ON & START position.
Does this sound about right.
I'm so sorry for all the questions, but I want to do it right the first time please bare with me it's truly appreciated!
Nick

...Roger...

It sounds to me like you could splice the dizzy in on the 12 pink to make it easier if you don't want to get into the bulkhead wiring.
The ACC lug is fused from the RADIO fuse so your running your radio,lockup and tach off the 20 amp radio fuse. If this works thats fine ,I don't know what the lockup requires for amps,the radio and tach would probably be fine on the same fuse. This fuse also has the TCS solenoid and hood door solenoid on it if those are still hooked up.
What kind of wiring diagram do you have,do you know where the 12 BROWN is that plugs into the radio capacitor that is mounted near the ignition switch on the steering column ?
I'm thinking you could run your choke,lockup,fan trigger and spares off the brown with individual fuses depending on the requirements of each item.
Anyone see a problem doing it this way.
I will admit 98% of what I work on is bone stock so other than adding HEI's I don't get into the add ons.
You could also, but I think its overkill for what your adding, use 1 relay for all the key on add ons (except the dizzy) and bypass the ign switch going directly to the battery or back of alt. which would take some load off the ign switch.

noonie

You guys are getting me confused

You can take the original coil/ign wire feed at the fuseblock thru the bulkhead connector, use it to signal a Bosch type relay powered from the alternator and feed all the stuff under the hood fused separately, except for the fans. they could take up to 25amp each so they require their own relays, but the first relay is more than enough to signal them too.
For interior switched, you could do the same thing, use your heaviest fused as a signal and grab the power from the battery.
New cars use relays for almost everything. You can get the relays and molded plugin pigtails for around 5 bucks a pop if you shop around.

Now's the time to get creative since it's all apart.

dembo

Finally had some time to sit down & have a look at the wiring diagram.
The lockup only requires a inline fuse of 2A. The hood door solenoid is not connected anymore as the the complete mechanism was shot. Neither is the TCS solenoid connected as I swapped my 400 for a 700 transmission. So i'll think i'll keep the lockup on the ACC lug
I found the 12 brown and also the capacitor. I think most modern radios don't require them anymore, or if I have too much interference I can add one later. I'll use scotch locks to splice in the choke & relay trigger.
Still have to look in my Haynes for a 75 diagram to see at what point the HEI is connected to the 12 pink.

The last 4 pictures also show some unconnected plugs in the engine compartment.
is this correct?
1 is the TCS transmission switch
2 is the Idle stop solenoid?
3 is the TCS solenoid?
They are all unused. I suppose non of them functions as a keyed 12V?
The last picture also shows a connector which I can't really find on the wiring diagram. It exits at the same point of the TCS transmission switch. Does anybody know what it is or where it's supposed to connect to?




Unconnected ones :







Thank you,
Nick

dembo

Ok, i smartened up and ordered a aux fusebox with 3 keyed 12v lugs. I think that will give me peace of mind and a better installation. Now i only need to find a spot for it. Still need to dig in and find the pink start & run hot for the hei and powerjection. Thanks Roger to set me on the right path!
http://www.painlessperformance.com/w...l=Street%20Rod
Does anyone recognize the connectors from the last 3 pictures?
Thanks
Nick