Adding relays
 

I am plotting on where to add a few modern electric upgrades on my 70 gmc. I want to run a power wire upgrade from the alt straight to the battery with a mega fuse and 3 relays (1 for a small fuse panel for accessories, 2 for electric fans.)

Just looking to get some ideas where you mounted them since the engine bays are so bare. Used to fords that have a nice starter solenoid on the inner fender.

Re: Adding relays
 

I put a Ford style Solenoid in my '71 GMC Jimmy to keep the Bendix solenoid from cooking off. It was too close to the header.
I did pick off one tap to run a 2nd Cigar Plug so I could run my GPS while the other one charged my mobile phone.

Re: Adding relays
 

https://www.amazon.com/dp/B0CDZCKBWM...ding=UTF8&th=1

These kits are really neat I added one on my frame rail

Re: Adding relays
 

Oh nice i have used a similar kit in my f100. Any pictures of yours? Just getting an idea where to put it.

Re: Adding relays
 

Painless offers terminal strip with a relay built in. I have one on my 98 Wrangler. Been 15 years and zero issues.
Pic. Just above and left of the brake booster.

Re: Adding relays
 

Have you read the Mad Electric article on where to tap into the system when adding loads for good alternator load sensing? Basically wiring things incorrectly can have adverse effects on battery life.

http://www.madelectrical.com/electri...esensing.shtml

This link goes to where I posted notes on how I tied a higher amperage alternator in with the factory wiring as well as adding air compressor wiring. Scroll to post 468. It may help with your project.

http://67-72chevytrucks.com/vboard/s...rnator&page=19

You may want to consider using a fuseable link instead of a fuse to protect the wiring in the truck like GM did. I upgraded my fuseable link as part of the conversion.

Re: Adding relays
 

where I mounted my headlight harness relays. Used my 30 amp AUX lead from + battery cable

Re: Adding relays
 

I went with a one wire altenator so it connects directly to the battery itself. I did my headlight upgrade relays in a similar location as 72SB did jis two relays. My fan relay is near the fan mounted to the rad support. My AC relay, anti theft relay, as well as my fuel pump relay are all under the dash.

Re: Adding relays
 

Tapping the original electrical system in the wrong place for heavy loads will mess up the balance used to drive your stock battery meter. The correct location is a PITA to tap. It is the main junction in the harness down on the left side close to the radiator support.
If you replaced the factory battery meter with a volt meter then connecting to the fuse link block next to battery is a better option. Tapping closer to the battery provides a cleaner power source as the battery acts like a capacitor, filtering any alternator noise in the line. Clean power recomended for things like engine management computers or higher end audio systems.
One last thing. Tapping at the main harness with a heavy load like fans can pin your factory battery meter if the alternator is not providing power. You also risk popping the fuses to the meter. You can correct this by upping the guage of the wire from main link to the fuse link junction block. This will reduce the sensitivity of the meter.
All this to point out that tapping a 50+ year old electrical system to handle modern accessories is not as simple as it first seems.
Oh. Do you have an alternator capable of pushing out the amps needed for the fans at idle? Will your external regulator last longer than a few hours under the new loads?

Re: Adding relays
 

Thats why I ran a new and seperate power wire for my asseccories accordingly. OE systems were not designed for the new additions

Re: Adding relays
 

Not to hijack this thread in any way, but I have an extra fuse box that is currently wired hot all the time. I would like to wire it to turn on with the key. Can I use a relay to set this up or some type of solenoid? Right now, it is only powering the seats.

Re: Adding relays
 

Yea just install a 30amp relay some where in the power wire that feeds the fuse box. Then wire the two coil wires for the relay with one to a key on power fuse or terminal and the other to a good round.

Re: Adding relays
 

Thanks!

Re: Adding relays
 

I haven't grabbed a pic yet but it's under the cab on the driver side for me

Re: Adding relays
 

That is exactly what I am planning on doing. In essence 12v off battery with a relay then use 12v switch to trigger the relay.

Whoever did this truck before me added a bunch of stuff and random stuff so trying to clean up and use a modern panel for now until I get around to re-wiring it. (need to finish my 55 chevy first which is going to take a bit)

Re: Adding relays
 

If you're installing a relay and it looks like a ford starter solenoid make sure you get one with a continuous duty coil. The regular starter relay coils are only meant for interment operation. Having it powered up continuously will cause the coil to overheat and fail. And they never give you the option to pick a time or schedule when it will fail. :lol:

https://www.colehersee.com.au/produc...duty-solenoid/

https://aviondemand.com/insider/star...uty-solenoids/

Re: Adding relays
 

Just finished up wiring this for a customer. 71 GMC. Previous---ahem, techs---not knowing what they were doing really had it messed up. Couple of weeks off and on working on this in the engine compartment, under the dash and down the rail to the trailer plug.

Re: Adding relays
 

When I added electric fans to my truck, I mounted the two relays underneath the core support triangle brace that's over by the battery. I secured the relays with the triangle brace mounting bolts. The relays are well hidden under there. I installed a little fuse panel next to the relays. That painless fuse panel with the built in relay looks like a cleaner solution than what I did.

I also ran a 6 gauge wire from the alternator to the battery and connected the other main system feed wires to it with a large crimp terminal in the stock junction location over behind the driver side headlight.

THOMAS & BETTS C Tap: 6 AWG For Max Run Wire Size, 29 Die
Model 54715

https://www.grainger.com/product/3LM..._WillCall&rfe=

Harbor Freight Hydraulic Crimping Tool
https://www.harborfreight.com/hydrau...ool-64044.html

Re: Adding relays
 

Are you all running volt meters instead of factory battery meter? Most of the connections shown in this thread will likely cause the factory wired battery meter to register charging when the shown connections are actually drawing power. A simple check is to have the key in the on position, motor not running. Look at the battery meter on the dash. Note position of needle. It should be on the "D" side of center. If in middle turn on your lights to draw power from battery to confirm meter is working.
Turn on the added accessory. If the needle moves more toward "D" for discharge you are wired correctly. If the needle moves towards center or even into the "C" side of guage than you have not tapped into the oem harness at the correct location rendering the battery meter useless.

Re: Adding relays
 

Good point. After completing the alternator upgrade and its associated wiring the factory ampmeter in my Burban no longer worked like it did before the upgrade. The guage would show discharge and charge but, the needle movement was so slight the guage was worthless unless you stared at from 6 inches away and didn't blink. :lol:

I believe this was due to the difference in resistance in the new wiring compared to the factory wiring. I could have experimented with resistors to restore the circuit back to factory specs but I opted for installation of a squarebody voltmeter in place of the ampmeter. Less work and a better indicator of battery condition.

Re: Adding relays
 

I installed the American Autowire 510871 voltmeter.

https://www.summitracing.com/parts/a...RoCpsgQAvD_BwE

Re: Adding relays
 

That looks Great.:metal:

I will have to bookmark that.;)

Re: Adding relays
 

I really like that guage. Do you have a pic of it in the cluster? It took me days to figure correct guage and lengh of wire from the fuse link junction to main splice to feed the electric fans and not numb or pin the battery guage. It works very well right now but that volt guage is very tempting.

Re: Adding relays
 

I posted some photos of the voltmeter in this thread.

https://67-72chevytrucks.com/vboard/...d.php?t=847577

Re: Adding relays
 

Nice that looks really clean. Can you expand on all what you have going on there? Just wanting to learn from other peoples mistakes.