Fatslobb

upgrade? very good idea. The later models have 80+A alternators, because they're necessary. It was done in response to many complaints that such as yours was insufficient. Yours is too small to run full load and keep battery well charged in extreme conditions. Just watch pulleys & alignments etc.

ARK_SWAMP_RIDER

Got my wiring upgraded today, did both battery grounds and positive lead with 4 gauge. I probably should have went bigger but it's the biggest I could find locally. Will be ordering the 140 amp alternator this week sometime.

Chickenman

A bad alternator is not going to drain your battery...

This is one of the BEST video's for testing your battery with a multimeter.

Like the video suggests, if you start the test with voltage over 12.4v (meaning you have a state of charge that is 75% or better) and if the voltage of the battery drops below 9.6 volts (not 10.24 or 10 but 9.6) during starting then the battery should be replaced.

Consequently you can also test the state of the charging system by using a multimeter. Connect it to the battery and start the vehicle. Turn on the heater, defroster, blower motor and the lights and measure the voltage. The charging system should be producing voltage between 13.5-15 volts. If the voltage is not within the specified voltage at idle, increase the engine rpm to 2500-3000 and measure the voltage (this simulates driving conditions). If the voltage is not within specs (13.5-15) then you have a problem with your charging system.

In response to a few posts ago, it is best to have a digital ammeter to measure current being drawn from the battery. Disconnect the positive battery cable from the terminal and plug the ammeter in series between the battery post and the positive cable. The current flowing (amps) should be no more than .03 amps. .03 is usually what newer cars use to keep the computers running (that's why the radio presets do not get erased each time you turn your car off.) If you find that you have more than .03 amps then you have some sort of a parasitic drain on the battery. Then next step is to go to the fuse box. Using a digital voltmeter measure the voltage flowing across each fuse (this is known as voltage drop). If the voltmeter measure .001V or more (this is the same as 1mV, the voltmeter might switch between volts and milivolts[mV] 1 volts = 100 millivolts) or higher then there is current flowing through that fuse. Pull up a wiring diagram and determine what might be using the electricity and unplug that particular unit (a light bulb or something like that). Unplug that unit and then measure the voltage going through the fuse that you tested prior. If you find that voltage dissapeared accross the fuse you have found the culprit.

I know that is a quick rundown, but if you need help send me a message or post up here. It is all pretty simple, its just understanding the concepts behind it all and getting used to the terminology.

ARK_SWAMP_RIDER

If it's impossible for an alternator to cause battery drain, why would the battery hold a charge overnight when it's disconnected but not when it is connected? I don't know much about this kind of stuff, but makes sense to me that the alternator would be a problem.

Chickenman

An alternator (or generator) makes electricity (a real basic explanation: by moving a magnet accross wires) it does not use electricity.

When you disconnect a battery from the car the entire electrical system of the car does not have power (including the alternator)!

Before you buy a new alternator try this. Completely charge your battery and put it in the truck. Disconnect your alternator from the electrical system and let the truck sit all night. In the morning connect your alternator and try to start the truck. Chances are the car won't start because its not the alternator that's draining your battery.

ARK_SWAMP_RIDER

Can't tell you why, but that isn't right. I've already done what you mentioned. Start with a charged battery, no problem cranking. Unhook the hot wire at the alternator and let sit overnight. Connected the wire the next morning and it fired right up. This was the only day since I purchased it that I did not have to jump start it. I did the same last night and it cranked again this morning, 2 days in a row, by leaving the alternator unhooked overnight.

Chickenman

So that means you need to check the circuit that the alternator is on. Might be a switch or a relay that is continually getting power. I would check everything out before I drop good money on an new alternator.

ARK_SWAMP_RIDER

Day 3 of leaving the alternator disconnected at night, no issues since. I have no idea what else to check on the alternator circuit. After a good big of searching I've ran across similar issues and the alternator was the culprit (as suggested by others here as well). I'm replacing it, it will be beneficial down the road anyway.

RAD4Runner

Concur

Good, job Chickenman.
ARK_SWAMP_RIDER, Here's a nice explanation of how alternator works

I really suspect the alternator, but please don't replace until you have identified exactly what's wrong, like Chickenman suggests. Could it be possible that some of the diodes in the alternator rectifier are shorted, or stator winding has short to ground, causing current to ground though stator winding? Try this:
Unscrew nut and disconnect thick white wire from "B" terminal of the alternator.

Measure resistance from the copper bolt to ground (i.e., ohm setting, red test probe on copper screw, black test probe on chassis ground/alternator body). You should get a very high resistance. I got 0.357 meg-ohm using my nice Fluke [0.395 meg-ohm with my HF special ] If you get significantly lower than that, you might have bad diodes or stator winding sorting to ground.

ARK_SWAMP_RIDER

I measured just as you described and got a very low reading. My understanding is this means 1800 ohms, or .0018 meg-ohm. Does this mean the alternator is toast?

Not best pic, but maybe you can read it. Set to measure 1k ohms and a reading of 1.8. The high reading (500) is far left, and low reading (0) is far right.

RAD4Runner

Looks like our analysis and actual measurements point to the alternator. Couple of other things-questions to other members
ARK_SWAMP_RIDER's measurement of 1800 ohms to ground means there's or are bad diodes in rectifier. However, 6.67mA of current draining through alternator rectifier/stator windings to ground does not seem enough to drain the battery overnight. Has anybody measured normal current draw on battery while car is off? Is it anywhere near 6.7 mA?
It seems that Rikoshay's statement of "battery and alternator as a couple" applies here.

ARK_SWAMP_RIDER, wanna double-check you battery? If absolutely good, get a new alternator. Consider the Jaguar 130A alternator- plug & ply except for pulley swap and minimal bending of mounting bracket.
Best wishes on the project

ARK_SWAMP_RIDER

The problem is that I'm not able to fully charge the battery. I was planning a trip to the parts store to get an alternator, I'll take the battery and see if they can charge it for me. Once it's charged, I'll measure it, as measuring right now probably wouldn't tell you much.

ARK_SWAMP_RIDER

What are your thoughts on this alternator? I know it's higher priced than other options such as the GM swap, but I'd prefer to have something that is a direct bolt on, not modifications needed. I know the GM swap (or Jaguar) isn't that complicated, but I'd be more comfortable knowing it was exactly the same as what I'm taking off. I'm still not 100% sure I'm comfortable doing this myself, I may see what a local shop would charge to swap it out. Seems like I have the worse luck with projects, so it may be money well spent. If a shop does it, not sure they'd do anything other than OEM so another plus for this kit.

http://www.lceperformance.com/Produc...80005&CartID=1

RAS86

Of course a "bad" alternator does not drain the battery, but it does NOT charge, or maintain the battery's charge, therefore, at night when the feller is in bed tucked in tight, that battery is draining like a ses pool at the carnival's portable. Therefore giving him a hard time to start, because his battery wasn't "fully" charge.

Just get the alternator, if the alternator has been replaced, and the problem persists .. you've found me another dumba**, but if the problem has been corrected, then hell, open a can of whoop a**, because you deserve it through all the bulls and headaches trying to figure out wth is going on with my damn Yota! (drink responsibly so you can drink again t'morrow).

Buy the alternator, turn in the old one to redeem your core charge back, grab a 12pk. of your choice of brew, and take it all in and look at the beast and be like, you almost had me ... psyche!!!!

Enjoy my friend.

ARK_SWAMP_RIDER

Only had the truck a week and already got a huge list of plans, so the budget won over. I found a 70 amp Bosch at Advance Auto for $100. It's brand new and carries a lifetime warranty, and hopefully will be at least some improvement over stock. I'll report back once I get it installed, which will probably be a week or two. Thanks for all the help!

ARK_SWAMP_RIDER

My uneducated opinion is that I disagree. If I leave the truck running and/or drive around, it will crank fine. This tells me that the alternator is charging the battery, but then when it sits for an extended period of time (a few hours) the battery is drained dead (presumably by the alternator).

Either way, I do have the alternator ordered and will see what happens when I get it installed.

SoCal4Running

There are 2 different splices on your Alternator wire before it gets to the battery.
Believe on the 88 there is one on the drivers side near the headlight and one on the passengers side to the fender side of the headlight. On my 86 their both around the passenger headlight.

Not sure where these splices go but do not think that the Alternator Wire is a solid wire from end to end. Worth investigating.

RAD4Runner

My educated guess:
Alternator has bad diodes. 1800 ohms from B terminal screw to ground is too low. My good, brand-new alternator see post above^^ has 400,000 ohms to ground. Therefore, it is not properly charging the battery. At the end of the day, battery is not fully charged- just barely enough to crank.
When OP leaves alternator B wire connected overnight the 6.67 mA drain (12Volts/1800 ohms) through alternator, plus other normal drain through the circuit is enough to drain battery so it can't crank.
Also possible that battery's weak.

We shall see.

ARK_SWAMP_RIDER

That's a good explanation. I never take more the a 5-10 minute drive in this truck so I'm not giving it enough time to fully charge. So, I don't know if the alternator isn't capable of fully charging the battery or if I'm just not giving it enough time (I'm thinking the latter).

If it comes down to it I'll replace the battery as well, but hopefully between the battery and alternator the issue is resolved.

RAD4Runner

Probably both;

1. 1800 ohms B terminal to ground is definitely not normal, so alternator is not working as expected (see Ricoshay's comment on ripple ^^),
2. PLUS you are not giving a weak alternator enough time to charge the battery.

Curious... Have you monitored charging voltage? Should be between 13.5 and 14.5 Volts.