ChrisJames

Ok I will do that. Should I use bigger cable for the ground wires? Also a new 4 gauge battery cable did come with the alternator but I'm not sure if I should disconnect the old battery cable on the alternator and run the new battery cable directly from the alternator to the battery or is there another way to connect it? What's your thoughts on that?

cruiser54

Yes.

www.kelleyswip.com has all the info you need.

ChrisJames

Wow. Yeah they have all the cables I need. Guess I have some upgrading to do. Hopefully that will fix my problem. Thank you.

sycoglitch

Yup. Hell, There's a chance those stock wires will catch fire or corrode now if you try to pull more through them.

ChrisJames

Yeah I'm going to upgrade. I checked out that website and they have everything I need to upgrade all the necessary wires. Hopefully that will help resolve the problem. Thank you everyone for your help.

ehall

Are you reading the voltage at the battery posts or using the dash gauge? The gauge measures voltage on the cabin power, which is isolated from the main power, and is really sensitive to accessory draw. Plus the blower motor controls (which feed to the blower motor) are fed by cab power, so when you put the blower on high, the gauge drops fast and hard.

Clean the terminals on the battery and alternator, tighten the nuts, clean connector terminals at the blower motor and headlight, add relays to the circuits etc, long term the only way to make the gauge accurate is to run a new wire from the gauge to the battery that is not on a shared feed.

cruiser54

It's what needs to be done.

I've done quite a few and there is a noticeable difference in the gauge reading.

But, as ehall mentions, the dash gauge is not the best indicator.

I took the ground wire for the blower motor and grounded it to teh passenger inner fender also.

NM-XJ

Just to clarify from a purely electrical standpoint:

Changing a 90 Amp alternator to, say, a 200 Amp alternator does NOT mean you have to upgrade your wiring. The 90 or 200 Amps is the capacity of the alternator...it doesn't automatically spit out that amperage. Electricity doesn't work that way.

You will only need to upgrade your wiring if you add load to the system, like more lights, a compressor, etc. If it is a stock XJ that did fine on a 90 Amp, and you haven't added more power consumption, then the 200 Amp will be fine without new wiring.

Let's do some math. Power(Watts) = Voltage (Volts) x Current (Amps). So a 100 Watt headlight operating at 12 Volts will always and forever draw 8.33 Amps. If you have only that one light hooked up to a 90 Amp alternator, it will only supply 8.33 Amps. Same for the 200 Amp alternator.

Now, let's say you add another 100 Watt light operating on 12 Volts. You have just doubled the power, kept the voltage the same...so the current the alternator must supply has doubled to 16.66 Amps.

BUT, keep this in mind. Wiring acts like one big resistor. So the longer the wire, the more the voltage drops from one end to the other. Think of trying to pump water through a very long skinny pipe. Now, if you upgrade your wiring to handle more current, it will by nature have less resistance...and thus less voltage drop. Think of taking that water pipe and making it a larger diameter. So a wiring upgrade could help you, but not necessarily because of the alternator.

cruiser54

And, our Cherokees are woefully "under wired".

It will help as many of us have witnessed personally.

NM-XJ

I don't disagree with you. See my last paragraph.

But I did want to dispel the notion that merely increasing the ampacity of your alternator requires a wiring upgrade.

sycoglitch

Iirc the OP did increase his load. He had audio equipment as well. And everyone knows that putting a larger alt doesn't mean it'll draw 200 nominal constantly. However it gives the chance for it too by added load. So why take the chance and as cruiser said, XJs came with horrible wiring. Damn, most Chrysler cars did.

ChrisJames

All you guys are a huge help with all this advice. I will upgrade my power cables and grounds. It's a 20 yr old vehicle so I'm sure it won't hurt to do so. Cable doesn't cost that much so I will start with upgrading that stuff and see what happens. If no change I'll let you guys know. Thank you all for your well appreciated thoughts and advice. I got to get this issue resolved before it starts snowing. I do alot of night driving. So all my lights and heater will be on drawing power.

ChrisJames

It's the dash gauge that drops and also a digital volt gauge that plugs into the cigarette lighter. That really drops with the heater on high and the headlights on. Drops below 13 volts. Between 12.2 and 12.8. When I turn everything off it will recover to about 13.7 but not the normal 14.2 to 14.5 volts that it used to normally stay at with everything on.

cruiser54

I wonder if my Tip #1 applies to your vintage Jeep also. #18

madmanmarty

Chris,I just upgraded mine.
My positive battery cable only had half the wire due to corrosion.
And the ground at the back of the head was down to 1/3 of its wire left.
The kit from Kelly's are all you will need to ensure the battery cables & ground wires are not causing your voltage drop.
With the accessories you have you need them anyway.