DIY DASHMOUNT CONTROLLED ALTERNATOR BOOST DIODE CIRCUIT

Many of you may want to copy my dash mounted 3 position switch controlled Alternator Diode Boost circuit you've seen in my truck where i can select NORMAL / MID / HIGH Output levels from my alternator and be able to switch it while the alternator is operating without damage.

basically how any diode booster circuit works is you are tricking the alternator to sense that the battery has 0.5 to 0.7 (tolerance) lower voltage PER diode in series by reducing that sense voltage that much as it passes thru each one. causing the alternator to increase its regulated voltage to compensate what it thinks is at the battery.

For example, if a sense output line goes open or the ALT-S fuse blows, then the alternator can go max output and damage itself. while switching "on the fly", you don't want a circuit that causes a break before make situation thus causing even a momentary open. my circuit ensures this never happens while switching the 3 position toggle (or two position if you want to create a hybrid of my design yourself)

Regardless, this can be easily made with a fuse extension from Amazon for 10 bucks, a few diodes for another 7 bucks (batch of 25) and a few bucks more for double pole triple throw (3 position) switch and wire and heat shrink etc....There isn't much current going thru this, however, the factory i believe used a 7.5 amp fuse for ALT-S to ensure that thing doesn't happen to even come close to blowing for current in normal situations because if the fuse goes, usually your alternator will go max out and damage itself if the thing is running. basically they are protecting the wire at the source and giving overkill rating.

however I decided to use 16 gauge wire and 10A rated diodes and switch regardless to maintain the factory ratings throughout the modified circuit

Basically get the fuse extension shown, cut one leg between the fuse plug and fuse holder and insert two diodes in series on the leg returning to the fuse plug. then tap three wires that come off there and then leave the relay box in the engine compartment, go thru the firewall (i used the grommet by the brake booster that on the inside is near the drivers left toes and then mounted a three position toggle down by the OBD2 port into the lower dash panel beneath the coin tray door)

I usually leave the switch in normal during longer drives to reduce alternator load and keep fuel economy maximized when Im traveling any good distance and have time to charge (still ill bump it up depending on my voltmeter readings my load usage (lights on at night or whatever). If Im at a campsite and just idling the truck or if i am night time and a short trip or whatever ill run it on the highest output. basically I have a voltage and ammeter i added and i can monitor my battery drain/draw/charge VS my situation and can switch it to meet the needs of my situation vs fuel economy (which really isn't that much of a gain unless trying to maximize extended highway MPG) but these days all the car companies have reduced alternator voltage output compared to the old days solely in an attempt to gain fuel mileage gains at the expense of shortening the life of batteries. and then one can get into discussions able lead acid vs AGM vs whatever but please keep that out of this post. this post is merely for DIY ability to have a switchable voltage regulation on the fly to meet whatever your needs of the situation.

Also... Note for those that may notice, yes, by increasing the distance (length of wire) between the battery and going back to the alternator sense input can cause increase resistances/voltage drop so even in normal they can be a slight rise in voltage depending on your wire run length and wire gauge selection. you can also just do this locally inside the relay fuse box with or without a switch. just hardwire the diodes to meet the desired voltage drop/ alternator output rise you want by again 0.5 to 0.7 (per diode in series if more than one diode used). all the switch is really doing is giving a short path around the diodes and never ever breaking open the circuit during switching this is HUGELY important if you want a circuit you can switch while its operating.

Enjoy......