Gang,
Just arriving at the need to move several modern electrical accessories from the my '66 98 fuse block ACC circuit off to a separate relay. Something in my after market stuff is screwing up my turn signals and overloading them. It's time to redo the aftermarket electricals with a design instead of organic growth (aka power supply spaghetti)

At the moment, most all the Olds electrical accessories from 1966 including cruise control, power antenna, rear cigarette lighters, power seats & power windows are run off the factory ACC circuit at the lower right corner of the fuse block. The factory provided for a 20 ro 30 amp fuse to be used to protect these options. I'm using a 30 amp fuse since that's what the CSM calls for.

But on top of all those factory toys, I've added a modern stereo, iPod, 02 sensors & gauge, USB outlet & updated digital guts behind a factory tach. My estimate is these additonal systems draw about _another_ 40 amps. It worked o.k. for a few years, but here & there something weird will happen, like the radio shutting off, or losing the ipod touch.

So I want to move all the aftermarket stuff to a separate relay switched circuit so that they don't draw as much through the key switch, nor through the ACC circuit.

A couple questions for you all.
1) Am I heading in the right direction moving high draw aftermarket accessories off to a separate circuit?
2) Do you all have a preferred part manufacturer / part number for what relay I ought to use? I'm thinking 40 amp, ideally GM style
3) Should I use just one relay for all the modern accessories or put 2 or more in series all switched by the ACC circuit for separability / cleanliness of install?

Thanks in advance for your views
Chris

 

1) If you don't do this you will continue to risk overload, low voltage (already signs of that), and possible fire. Our cars had marginal wire gauge from the factory. You do need relays if adding any significant loads.
2) Most of my relays are in a dry location, so I used the old-fashioned ice cube relays. I have one relay in a wet area under the hood and for that I chose a modern relay housing with sealed connector and waterproof cover over the ice cube.
3) To keep voltage drop low, use multiple relays--each one handling 30 amps or less or serving a major load such as cooling fans.

Source relay power from an under-hood power point where the alternator and battery leads intersect. The lead to the battery may need to be upgraded. You may need to upgrade the alternator and its supply wire. Locate the relays to minimize wiring work.

Make sure you have fuses or fusible links at the origin of each relay-supply wire.

I used one relay to create accessory supply voltage so that I didn't overload the existing accessory circuit and fuse.

 

It depends on your budget abs how fancy you want to get. There are countless add on relay panels available in the aftermarket, plus countless option from the junkyard.

Find a relay design that fits where you want to put it, and that will handle your expected current needs. Leave a little room for expansion. Run the power supply wire to the battery (make sure that wire is protected by a fuse or circuit breaker) and use a relay to trigger the power feed.

Del City, WayTek, The Electrical Depot, painless wiring, American AutoWire, all offer add on fuse panels. Some are weather resistant, others need to be inside the car.

 

Gents,
Completely agree that GM was penny focused on wiring gauges in the 60’s. I’ve seen a fair few 65-66 big Olds in the boneyard with trashed and melted harnesses. Usually accompanied by a lot of shady shade tree aftermarket wiring. I have a couple of spare harnesses under the house, basically one for parts and one good spare.

I’ve long since modified my main harness to put thicker gauge wires on high amperage circuits like the alternator output and starter motor. My battery and horn relay/junction block are 1 or 2 gauge now. Thick. That junction block leads to a 40 amp circuit breaker for the convertible top and other unswitched accessories, so there’s ample opportunity there.

I just hadn’t focused on whether or not I was overloading the switched-ACC circuit. I had faith in GM’s design, but as loads grew, I never stepped back and thought through the potential for overload. Now is the time to do that. But I want to do it right and document it, so I know what I did years from now.

Thanks for the tips. Hadn’t considered a relay to trip a relay or 2 in the name of lightening the load on the ACC circuit. Good idea at the cost of some complexity.

Sounds like a good solution would 2 relays to split the high amperage duties:
Tach (3 amps) + 02 Sensor (9 amps) on 20 amp relay A;
Car stereo (10 amps) and USB plug (5 amps) on 20 amp relay B.

I think both relays would be dry, I.e. inside the cabin mounted to the firewall. The idea would be to have the keyswitch trigger the relays and power on the accessories. Would you tap into the keyswitch itself or tap into the ACC circuit on the fuse panel as I have before. The fuse panel mod would be more visible, so I’d know what I did, but tapping the actual ignition ACC line upstream of the ACC circuit might lighten the load on the ACC circuit even further.

Am I correct in thinking I’m looking for 20 amp, normally open, 4 or 5 pin relays? It possible I’ll put some more electrical doo-dads in later on down the line, should I get 2x30 amp relays just in case? I’ll got check out Del City and the other you mentioned, but if anyone has recommended part numbers, I’m all eyes.

I’ve got a deliver-daughter-to-college trip next week, so this is a good project to design on the road and build after our girl is gone. I’ll probably need a project once she’s away…

Cheers
cf

 

With all the newly added items you will need an alternator that puts out alot more amps. I got one that looks factory and puts 135 amps out.

 

Chris, you've got the right ideas. No need for our preaching.

In your design phase, you could focus on reducing the loads carried by wiring inside the cabin. These loads weigh on aging connectors with years of corrosion, causing heat and voltage drop.

Rethink how the heaviest factory loads could be reduced or eliminated--just for the future good of your "penny-focused" (love that term) wiring system. A suggestion would be to use a Ford-style remote solenoid as a relay to switch battery current to your starter solenoid. This would reduce the load on the purple wire circuit inside the car from 40 A to 3 A. And it would forever eliminate the chances of having hot-soak starting problems.

Gary

 

Bosch style relays are generally at least 30amp. I'd get a couple of fused 12v relays with socket, use the ACC connection to trigger the relays.
Using your wiring scheme you are well within the capacity of the relays.

 

A relay to trip a relay is over kill. The primary side of a relay draws very low amps. My advice is to split your extra loads between two 40 amp relays and trigger both with the acc. Circuit, the primary side of both relays is way less than the loads you have added to that circuit thus far. I agree to power the secondary relay circuits directly from the battery or horn relay fused appropriately. Good luck. Once you get the relays you decide on. Draw up a schematic to help you understand what you want to do.

 

Don't overthink this, an 8 circuit fuse block is under $20 and a continuous duty relay to power it is also under $20. Use a keyed source to trigger it and move anything that is not stock over to the new fuse block.

 

Gang,
Thanks for your thoughts. Great that we can help each other. Car in question here is a mildly modified ‘66 98 convertible. Thoughts below pertain to most any ‘65-‘70 big cars, more or less.

Catching up the last few posts:
My alternator is an internally regulated 105 amp 10 or 12 SI. It’s formally wired with a 6’ sense wire connected to the driver’s fender junction block. That means I’m not using those convenient jumpers, but am getting a real average voltage value in the charging system. My glovebox volt meter reports a steady consistent 14.2 volts. The output wire is like a 12 or 10 gauge, so resistance, even given heat, has been rock solid. I feel like the charging side is solid. But your logic about a bigger alternator is right on: when you load up the demand side with a bunch of toys, you’d better build up the voltage/amperage supply side too. For originality sticklers, the alternator looks wrong, but it works great and I drive this car as much as I can.

Agree that relay to trigger a relay is overkill my needs. There’s probably a good use case out there, but I don’t think my car is it.

VC — you’ll laugh. But I’m so conscious of corroded connectors that I have used a tiny screwdriver to pop out factory high amperage brass connectors, dremel clean/polish them, then reinsert into their plastic shells, just to make 1966 good hardware last. Mostly I’ve done this on high-load male/female spades in the engine compartment, but also here & there in the passenger cabin too.

I haven’t had starter heat soak problems in years, since bumping the gauge of the starter motor connections and negative cable to the battery to bigger wires. Hot starting has been gone since I converted to HEI, internally regulated alternator and added big thick battery cables with clean connections. I could get fancy with a remote starter solenoid, but I feel like leaving it factory, provided it’s really reliable, is probably best over the long term. Plus, unless I document what changes I make, I’ll forget them and the next owner is totally scr*wed.

So the basic design sounds about right? I mean 2 X normally open 20 amp relays wired in series to the ACC circuit. Each one controlling about half of the aftermarket amperage draw among the 4 accessories.

After digging in, I’m leaning toward solid state relays (SSR’s), not the traditional magnetic kind. Points wear, solid state should last longer. Maybe SSR’s work a tick more quickly too. Apparently SSR’s have a gulp value and continuous value. Gulp value is the spiked draw on startup, continuous is what they’re rated at for long term usage. I’m still getting used to the pin out & verbiage, but I think I need a gulp value of 40 or so and 20 amps or so continuous.

<< Anyone have suggestions about the best SSR for my application here? Especially one with a diode to prevent voltage feedback? I’m on the hunt. >>

I got the jpegs from various aftermarket manuals today to draw up a design with pinouts. My process for this kind of thing is paste the Jpegs into Visio, then draw colored lines to represent the wire connections, usually with lots of labels on the wires to tell me what to do. I’ll post it after I get it done. Designing is a good airplane project.

Software helps: I’m experienced in Visio, but on the MacOS side, Omnigraffle looks good too. These diagramming programs have gotten good. Years ago I scanned (and eventually redrew) my ‘66 big car wiring diagram in Photoshop. It’s been a great help to have an accurate wiring diagram in situations like this where I’m digging into previous work and can’t remember what I did.

Anyway, looking forward to your SSR suggestions and others you may have to offer. If I get it right, the logic here could save a fair few wiring harnesses from the dreaded meltdown.

Cheers
Chris

 

Eric - right on. That’s exactly how I’m thinking.

Cf

 

For some people, the planning PROCESS is just as important as the installation. That's just in their wiring.

I can't do a project without running through all the permutations in my mind. And then I draw a flow diagram to generate other thoughts. And ask other people for advice, etc.

But when the project is done, it's usually perfect (to me, anyway).

Yes, I need to constantly keep your advice in mind to get a good balance of process with progress.

 

I like my Cirikit Boss from Painless, easy install, has both keyed and always on options. I installed mine behind the kick panel.

 

DC2x4drvr,
Many thanks for the steer on the Painless Kit. Just put the order in for a 4 switched circuit 3 constant part. Painless makes a good variety of these kits from modest to high amperage 7 circuit. I liked the idea of the modern fuses and relay looking different from the factory stuff. It will remind me that I’ve hived off these circuits separate from the factory harness. Colored wires will help too.

Not the biggest Amazon fan, but if anyone’s following along, you can find it here:


I’ll keep you all updated on how this all works out. It’ll be a couple of weeks before it goes in the car.

 

Took a couple hours to begin the clean up and circuit switching. I've solved the problem short term, it seems, but longer run I'm looking forward to hiving off the modern stuff to the Painless 10701 Kit.

First I checked the keyswitch leads just in case they'd suffered from overheating. No melting detected at all on the plastic shell and it looked in great shape. The switch itself is only a few years old and as clean as a whistle.

For a long while, I had the modern radio switched circuit hooked in the orignal factory radio 7.5 amp circuit, just sistered/jumped on the factory yellow radio power wire. I never run both the modern radio and the factory AM/FM together so it's never blown a fuse. But in the name of putting factory back to factory I moved the modern radio switched input to a factory red/white male lead on the passenger side up above the glove box. This red/white lead is switched by the relay in the driver's side kick panel which also feeds the power seat and power windows so it handles very high amperage.

Short term, everything's working properly again. I'm still going to put the accessory relay in just for cleanliness, but it's great to have perfectly functioning turn/stop lights again.

Just to make a note of it, in the '66 big olds factory harness, there is one unused Orange coloerd Battery lead by the ignition switch. I believe it's for the accessory light system, but I've apparently powered mine some other way. The other big aha is that Olds provided a relay switched Red/White lead above the glove box which allowed me to move the modern radio off the ACC circuit and drop the draw which was causing the turn signals to fail.

If I remember correctly, my '66 Starfire radio (identical head unit) is also powered by that odd relay switched lead. That explains why I never had a problem with that radio.

Cheers
cf

 

cfair:
Don't forget to upgrade your ground connections while your working on the supply circuits; specifically, the ground wire between the neg post of the battery and the body. From the factory, this wire was ridiculously small, like 14-16 gauge, and it connected to the driver's side fender or radiator support which is then bolted to the cowl (where most of the factory circuits are grounded). Over the years the conductivity between the fender/radiator support/cowl gets rusty or corroded and the resistance in this ground path increases. If you're not too concerned about originality, I would run a large 4-8-10 gauge ground wire directly from the neg battery post to the cowl to make sure all your factory and aftermarket add-ons have a good, low resistance ground path back the the battery. There should also be a large ground strap between the engine block and the body, but this wire tends to get corroded or left off after years of under-hood clean up and engine overhauls, etc.

Excellent choice selecting the Painless fuse kit. I've seen some pretty questionable "Chinesium" fuse block kits on Amazon & eBay that looked like they would simply melt once you powered up all the circuits. Run a dedicated V+ wire from the battery to the Painless fuse block, and use a fuse or fusible link wire to protect the wire feeding the Painless fuse block. Connect your new fuse block directly to the battery; don't be tempted to use the power taps on the factory fuse block. You need a dedicated feed for your aftermarket add-ons to remove the loads from the ignition switch and the factory wiring. You can buy the special "Pico" fusible link wire on Amazon. You only need a short section (4-6") for protection. The general rule is to use a fusible link that is 4 wire sizes smaller than the gauge of the wire you're protecting, i.e. 14 gauge Pico wire protects a 10 gauge wire. 14 AWG Pico is part# 8125PT and will work for your application. Good luck, and post pics of your project.

Rodney

 

Go to Amazon or ebay and search for "fused relay" and these things pop up. Pick the one that fits your needs, pay, and they come to you. Connect the load lead to the horn relay, battery, or other such heavy duty power source and the trip lead to whatever circuit you want to expand. The power out can then be connected to whatever accessory you wish. Clean and dress the wiring to your own satisfaction and you now have a fused, switched accessory circuit(s). It's as easy as that. The relays can be installed where ever they are needed or grouped in a central location for easy inspection and maintenance.

 

X2....great product.

 

On a trip to get our older daughter to college.

Killed an hour or 3 today designing the wiring circuit mapping aftermarket to the factory harness plus each aftermarket device to relevant switched-positive, battery-positive and ground leads. Not even talking about the cluster lamp illumination options.

It’s been a good exercise to work out the connection-by-connection wiring to foresee the weak points and things I’ve got to pay attention to. The big “a-ha” was discovering yet again the value of preparation vs. problem solving on the fly in the middle of the job.

I’ll get to the physical work next week, but I’ve got a much better idea tonight of what to do than I had 2 days ago before mapping the layouts on a computer.

In the old days, I would have just read the manuals and cobbled up something that worked over a night or 2. Design > cobbling together something that works.

Cheers
cf

 

I have a couple of '66 big cars with modern accessories. As I added stuff, I've been a little careful about thick wires, grommets through the firewall and a stronger alternator, but never really formally designed anything. I pretty much just added switched circuits to either the ACC circuit or the power window relay and that was it. Until recently I've never had a problem adding electrical stuff to my cars.

When the turn signals in my 98 started acting weird, I thought it was time to separate the modern stuff from 55 year old wires. Modern accessories draw a fair amount of amperage through wires & switches which GM never intended to carry these loads. I still haven't quite solved the turn signal mystery, but at least I can rule out modern accessories as the source of my troubles on the convertible.

Alternators in the 60's delivered about 50-60 amps or so. This was adquate for the electrical loads as desgined. I've been using a later model ('85 Riviera) 12SI alternator which puts out 95 amps to make up for the accessory amperage load. In my experience it's been enough to work well in my cars, but there are more powerful alts out there if you need.

In my case the modern accessory amperage load is maybe a little larger than average:
1) Modern stereo: a head unit, 2 amplifiers, speakers and a 10" sub in the trunk. My guess is this is 10-20 amps in operation (and it's on most of the time while driving)
2) Innovate dual oxygen sensors, gauge and related digital hardware. They advertise 9-12 amps for everything but the sensors themselves which use electricity to warm the 02 sensors, so I'm guessing about 20 amps there too. It's on all the time too.
3) 3 USB outlets (1 front, 2 rear) which provide 4.8 amps each at max output, so there's another intermittently used 15 amps.
4) Digital guts in a factory tach, another 3 amps and on all the time.

All of that is on top of what Olds used to run the car - ignition, transmission, headlights, heater/AC, etc. The basic idea here is to use the Olds "ACC" circuit to trigger a separate relay to power the modern stuff. The trigger load is tiny, just 3 amps, as compared to the sum of 40-50 amps above.

Initially I was going to roll my own harness, but from you all I learned that was the hard way.

Someone here suggested the Painless Kit 70107. This provides 4 switched circuits, 4 unswitched and a convenient ground on the firewall mount.

Unboxing the Painless Wiring Kit. I'm not affiliated, just a happy customer.

The wires come in a nice neat roll with very disctinct colors for each circuit. That helps us color blind people. The Red main power in wire (goes through circuit breaker to battery) is both heavier gauge and much longer than the output wires. They didn't cheap out.

Having said that I did use a few Packard 56 shells & terminals, plus a few universal electrical connectors and a bunch of 3/16" shrink tubing in several colors. Point is, you'l need just a bit more than the kit here.

I mounted mine with the realy on the right and flipped the fuses. The ground mount is hidden in upper right corner here.

Delivering my daughter to college gave me a chance to make an actual wiring diagram and was kind of a fun airplane/hotel room project in itself. If anybody wants to see that, let me know. Turns out doing the project in my mind helped me discover challenges before doing the install.

A little mounting trick. I use blue tape & a sharpie through the mounting holes to make a sticky template for the circuit breaker & the fuse block. Then you stick the tape to the firewall and drill exactly where you need. Mocking it up first is great for safe & clean placement.

Make your own sticky mounting templates with blue tape & a sharpie.

I've had these cars for long enough that sometimes I curse myself as the previous owner. Over the past few years, I've gotten more careful about labeling changes to the wiring harness with a Dymo Rhino 6000. When things are labeled, it saves me hours of trying to figure out what I did 5 years ago, or maybe did wrong 5 years ago.

Here is the fuse block & wires labeled for easy reference later. Each circuit on the fuse block is labeled so when a fuse blows I know which circuit went wrong. I alse made 2 sets of on-wire labels: one for the fuse block end + one for the connection to each modern component: USB outlets, O2 Sensors, Radio, and Tach. Unused circuits are safely ziptied out of the way for future use. I like the fact that this relay & fuses look different from '66 Olds vintage electricals. Makes it very clear that this is not factory.

Circuit isolater labeled to make maintenance down the road much easier.

So that's the bench stuff. The on-car stuff is actually not that hard, mostly since the systems I'm powering were already in place. At heart, I was just switching power sources to things that were already operating correctly. It was less work than I was expecting. As you can imagine there's a bunch of soldering and crimping. I've gotten in the habit of using the Packard 56 system of terminals & shells like GM did in the 60's. Feels more correct to me than generic universal electrical connectors. See the Auveco catalog if you like the approach.

Here's the final install:

Modern accessories powered by modern relay. Isolated, easier to maintain, and safer than lots of amps through 55 year old wires.

Guessing it took me a day or 2 from start to finish, but I was in no rush on the diagram or labeling which are distinctly optional. Nice weekend project. Comments, suggestions or thoughts most welcome. I haven't driven too many miles yet, but I like the way these are performing so far.

Hope this helps,
Chris

 

I merged your 2 threads as it seems only fitting to have closure within the original thread.