mortymower

I am about to make an auxilary harness for my headlights and I was thinking about making it also run my cooling fans. The reason for this is because when the engine is running, no fans/ AC/ headlights/ or anything major running, I have about 14 volts at the bat. However with the A/C on full blast, and once both fans come on high, my bat voltage drops to about 12.7 idle and barely 13 while reved up to 3K rpms. Once I add the headlights and fogs, that drops to 12.3 at the bat and 12.7 reved up. People said that making a light harness eliminated the voltage drop for the lights so if I tie the fans into a new heavy gauge harness right from the alternator, wouldn't that reduce/ eliminate my voltage drop when they are on?

eniac

It might but it could be your alternator not putting out what it should. Heat kills the efficiency of the stock units. When you first start the car cold with the A/C and everything else on, does the voltage drop just the same?

Since I switched to a smaller, more efficient alternator my voltage barely moves no matter if I have the all the lights on bright, a/c, radio, fans, and the countless added electronics on.

Be sure to check your alternator and grounds before going through the effort to bulk up the wiring.

Jeremy Himsel

Yeah but the voltage drop the headlight harness cures is the voltage drop between the power source and the actual head light connection light due to 20 year old corroded wire. Redoing the fan harness may give you an increased voltage @ the fans but will not change the overall load or drop at the alternator or battery. Your best bet would be to install an adjustable voltage regulator.

mortymower

Oh okay, I have a receipt for a new alternator in the PO's folder about 3 years ago, and I put in a new voltage regulator about a year ago, so I think the aternator is good but maybe not. I will check my grounds and all connections.

And as a response to the first reply if I crank it up and imediately turn everything on, the voltage drops just as it does if it has been running for a while.


By the way Himsel, have you started on the fifth gear yet, or are you still playing with all of your new chromed toys

Jeremy Himsel

The stock regulator is like a 14.1 volt regulator. Switching to a 14.4 regulator, like Ice Shark did, makes a huge difference and they're like $15. If your battery cables are original then they need to be changed. Especially the ground cable. You can use a Transpo IB 373A AVR if you decide to go that route.

mortymower

Thanks I'll look into that, where do you get a 14.4 regulator.

Jeremy Himsel

Call just about any local alternator/ starter / elecrtrical motor rebuild shop and they can get it for you. Just give then that part number and don't even tell them it's adjustbale. They were like $12 last time I checked but it's been a few years.

mortymower

So if its adjustable what is the range?

marky522

Actually the main reason you see such a large improvement is you stop the current from flowing through the light switch, by making that a low current control circuit, and not a high current switch. Your fans would be much more effiecent if you did wire it that way, but it isnt as simple as wiring in a fan, you would need to utilize a resistor and multiple relays for the different speeds.

Mark

bearone

the batt needs to be fully charged or gage voltage will be goofy.

when i did the alternator i did the batt harness and now see a squeak over 14 after starting, up to temp/both fans on, a/c on, lights on, i'll see just a little under 14 with the stock regulator.

the volt gage can be calibrated to a decent dvm with a small set screw on the side of the voltmeter.

87951
95sl320 dd

Got Me a Porsha

Actually, the 16 gauge wire (barely adequate when new) and twenty-year old grounds are the most detrimental to the lighting circuit. The switch is just a weak link, and cannot tolerate any increase in current without letting out some magic smoke.

The reasons behind the headlight harness upgrade are to support the upgrade to larger wattage headlamps, and also very likely to bypass the aging factory wiring. As for the electric fan harness, unless the fans have been upgraded resulting in additional current requirements, it should be adequate provided it is in good condition...as well as the rest of the charging system.

I have installed Jeremy's upgraded battery cables and grounds, headlight harness of my design, adjustable voltage regulator (14.4v), new alternator cooling hose, and an Interstate battery in my 951. With 90/100 E-codes, 85W yellowstar fogs, and 100W driving lights...A/C running, cooling fans, and plenty of stereo...I still read 13.7v at the battery, at idle.

The key is to make sure everything is in top order.

marky522

16 Gauge wire can handle 20Amps which is more than plenty for the factory
headlights, and your entire statement agrees with what i said, the reason you use the relay setup is to take the load off the older factory harness, and thus will allow you to run your higher wattage headlights. You dont bypass the factory wiring you make it the low current control side of the circuit. I agree the fans dont need the relay setup, just pointing out it would work..

Mark