Voltage Regulator Upgrade?

First off…

I have a 1969 XR7 Convertible with a 351W M-Code and Power steering and an aftermarket A/C system.
So my question is, if I upgrade my alternator to a 140 Amp unit do I need to change the voltage regulator and possibly wire sizes to accommodate the available larger current draw? Not even sure there is such a thing as a more powerful Voltage regulator.
I’m increasing the alternator because I’m looking at changing out my belt driven Power Steering pump for an electrical unit and they draw 40 or more amps of current and I feel my stock alternator won’t be powerful enough.
Appreciate any thoughts on the matter.

If you go to a modern 140 amp alternator then you would be best off using a regulator made to work with that alternator. The stock wiring is only good for maybe 60 amps so all of that needs to go too. Probably the only solution would be something like a Painless wiring harness or make a new one yourself.

Every modification that you do will cost twice as much as you think and require a lot more effort than you think.

I would suggest an internal regulated alternator like a 1- wire or 3g style.


Both basically hook up via one power and ground cable so very simple to install. You eliminate the factory external regulator and wiring. I installed the first option, super easy and looks like it belongs. Building cables was hardest part but really not hard at all.

Appreciate your response.
So you wire the regulated output of this single wire alternator, through a circuit breaker, to the battery or starter solenoid?
Just keep the current regulator in place and leave the output (4-pin) connector attached as it is? Just unplug the 3-plug connector form the original alternator? I’m concerned that the 4 wires that come out of the original regulator go to several different circuits in the wire harness and removing it will create issues.

Shows a V belt when I click on it - look at the 360 degree view.

The first link will include a v belt pulling installed. This is the one I installed on my 68. It’s a one wire install with an internal regulator. It will have the external fan like the original. It’s a 150amp output

The second is a 3g alternator and has an external regulator mounted to the alternator. It’s more of a later model style but will bolt in as well and is a one wire install as above. It will include both pulleys, I believe the serp belt is installed and the v belt comes with. It has an internal fan and output is 120amps

If you check powermasters site they have instructions on retaining the amp warning light as well. If you have an amp gauge you would need to convert it over to voltage.

For those that want to upgrade alternators with the existing wiring, is the Powermaster 7078 a reasonable choice?


In addition, is it worth while moving towards an electronic regulator such as


Regulators regulate voltage, not current. A modern solid state regulator plugged in the factory harness will do just fine. The amount of current pulled by all of the original equipment won’t change so the existing wiring harness will be fine. Any new devices that you add will need to be connected with a supplemental wiring harness and fuses. The alternator is capable of high current but it won’t put out any more current than required to maintain system voltage.

+1. Your electric steering needs to run directly off of the battery with an inline fuse or relay, and should avoid the use of any factory wiring.

I agree, most of the aftermarket Holley EFI electronics that I’ve added require a direct connection to the battery for the best possible power quality.
In this case were talking such a large amount of current required to run an electric PS pump, large gauge (#8) wires directly to the battery would be appropriate.
I guess the place I get a little fuzzy is now the battery will need additional current into it to recharge it, I guess that is fixed by having a larger diameter wire running from the new alternator to the battery/starter solenoid.

Most certainly you will overcome the ability for the alternator to keep the battery sufficiently charged with the addition of high demand electrical items such as electric power steering, Electric fans, efi etc.

Most devices do recommend a direct path to the battery to ensure good clean power. Eventually you end up with a whole gang of wiring to the battery so be thinking a junction buss bar/fuse box setup to clean everything up. Remember the battery is there for “reserve” power and for starting purposes. You want the alternator to be able to supply the power to all engine control and accessory’s during normal operation.

Speaking of electric power steering. I have been looking into that as well, I like the idea of no pump, hoses and ram. Would really clean up under the hood and simplify things.

The electric PS system I’m looking at implementing is a Volvo Electric hydraulic system (5N51), so I’m not really cleaning it up too much, just getting rid of the belt to the PS pump and possibly adding a few HP’s at the wheels. Actually the main reason for the conversion is to allow for my aftermarket A/C compressor to have it’s own dedicated belt. The current A/C belt configuration (not stock) shares the belt to the PS pump, and it’s a compromise of both pumps (A/C compressor and PS) ability to not squeal and squeak or flat out not spin (as is the case with the A/C compressor on very hot days).

Also, I found this company sells a G3 alternator and wiring harness with a regulator so you can keep all your exiting wire harnesses. Might be worth a look. It’s only 95 amps but that’s better than stock by 50%. https://www.paperformance.com

Keep in mind that generally it takes twice as much power to drive the alternator than the device the alternator is powering. You are converting mechanical energy into electrical energy and then back to mechanical energy. If the problem is a squealing belt you are going about this is a pretty convoluted way. It will probably take a double pulley belt drive to operate the alternator if you really do need to get rated power out of it. Look at the way the factory AC is laid out and that will point you in the right direction to solve the belt issues.

The aftermarket A/C system I added to the car cheats big time on the whole compressor belt setup by just using the existing PS pump’s belt circuit.
What this did was take ~50% of the PS belt to pulley contact area away, and the Compressor’s belt contact surface is also limited which has caused this to slip in heavy load conditions.
I looked at the factory A/C belt system and to implement it would require several brackets and idler pulleys that are pretty expensive and\or unattainable. If some one has a donor car that can supply me the parts I’d certainly be interested and willing to pay $!
From what I read on the internet (and it must be true! :wink: ) the PS pump uses ~8HP, while the added load on the alternator is ~1HP. Now going from a 60 amp alternator to a 95amp alternator could indeed load the engine more I agree with that probability.
Looking at all the sites that have alternator upgrades they never indicate the belts need to be resized or doubled up.
And IMHO; If alternators take twice the mechanical energy then the mechanical equivalent to perform the same task, why have so many systems in cars become electrical ? Radiator fans, PS pumps, even water pumps (in some cases) have been converted over to electrical. Not trying to be combative, it’s just my thoughts.

One horsepower is roughly 750 watts. Power, measured in watts, is equal to current times voltage so that tells us that at 15 volts we need 50 amps of current to make 1 HP. So an alternator that can put out 100 amps of current at 15 volts can produce 1500 watts of power, roughly 2 horsepower. However we have to convert the mechanical energy of the engine (the rotation of the crankshaft) into electrical energy in the alternator. Since we know that there is no such thing as perfect energy conversion, it takes the engine more than 2 horsepower to turn the alternator. Typically the alternator itself is about 60% efficient meaning that if you put one horsepower of energy into it (750 watts) you will get 450 watts out of it. All of this is physics so pretty much not a matter of opinion.

So why so many electrical things on new cars? Fuel mileage is number 1. Start / Stop technology means things have to keep working when the engine isn’t running. Power steering, cooling fans for radiator and AC condensor need to keep going. Even where start / stop is not used engines are not efficient at idle and idle mixtures have run richer to make a little more torque, or in some cases idle speeds have to increase to accommodate the accessories. It is also possible to computer control voltage regulation to minimize the rate of charge when the engine is at low RPMs, and to do most charging at higher RPMs. When you no longer rely on the engine for power you can begin to modulate things like steering effort and braking effort electronically. Almost everything in a modern car is being operated by a computer that is communicating on a bus. It is easier to build in functions electronically than mechanically.

I’m an electrical engineer who before working on ABS, RSC, TC, YSC, regenerative braking ,etc., was working on Electric Power Steering. What you’re talking about is what we called Electrically Powered Hydraulic Steering (EPHS).

A steering system experiences it’s maximum forces when you are turning while braking. Think of that case where you see your turn a little late, or that parking space that you almost didn’t see. And when this happens your engine is at idle.

An engine driven PS pump needs to be sized to provide enough fluid flow and pressure to move that cylinder when the engine is at idle

I think XR7G428’s point was that every watt or ftlbrpm of power used in your car comes off the crankshaft. There is no other source. The mechanical systems have their load more or less constantly. The PS pump is a good example of a fairly constant load. The benefit of an EPHS system is that the motor operates at a reduced output (speed) under low steering load situations. That means there needs to be sensors to determine when the motor output can be reduced and when it needs to be increased to maintain the assist level and controllability. When the pump output needs to rise to keep up with the steering demand, the electrical load will also increase. Some of this will be immediately supplied by the battery, but the voltage regulator will quickly see the falling voltage and increase the field current to the alternator, which will increase the torque it is applying against the crankshaft rotation, the only power source.

Without the sensors and controls, your least unsafe option is to run the pump full tilt, which is a loser on the efficiency front as XR7G428 alludes to above.

What you are both saying makes complete sense, I appreciate you clarifying your points to me.
Sounds like I wasn’t that far off from the 1 HP added load, since the electrical PS pump draws around 40 amps.

So my best solution is to find a donor car that had A/C and salvage all the A/C brackets, idlers, crank pulleys etc. to implement the factory belt system?
With that option possibly not available or cost prohibitive, the next best possible course of action would be?

I think keeping the two belt system I currently have and having a dedicated belt for only the A/C and an electric/hydraulic PS system, although not optimal, is a viable solution and possibly much less expensive.

I also have a 69 M code vert. As you may have surmised I live in the Detroit area, so the car is stashed away for the winter. Otherwise I would post some pictures of the belting. I think you need to be able to move the compressor forward, find the accessory pulley that bolts to the front of the vibration damper, and then an idler to tension the belt. That would set you up with a belt that only runs the compressor and restores enough wrap to the PS pump pulley.

I would start by checking with the add-on A/C supplier. This can’t be the first time this has come up. Add-on A/C has been around longer than our cars have been.

One other thing to keep in mind about our vintage alternators is the rated output is when the alternator is cold. As the windings heat up, their resistance goes up and the maximum output goes down. Something to keep in mind for adding electric fans or water pumps.

I was thinking the same thing. They may have a solution available, I’ll contact them on Monday. The Compressor bracket does look like the compressor could be mounted farther out so a 3rd belt could catch it. One of the issues with the (alternator side) idler is it requires a special spacer/bracket, that is not available at WWCC so I’d have to source it somewhere else (even if WWCC had one in stock they wanted way too much for it). I guess I could attempt to fabricate it. Not sure if the idler on the drivers side requires any special bracketing to mount correctly.