Automotive Electrical Problem

Grounded? Ok. Properly? I don't know. Better check with an ohm-meter what's the resistance from battery minus to engine block.

I don't know what you mean by 'terminal block' and which connection you put the meter's probe on, but I'd check the plus-connection of the starter motor if I were you. If one should expect a voltage on the 'terminal block', then you must already have found the problem: a broken cable or (very) bad contact from battery positive pole to the terminal block. (Also to the starter engine?).

Nothing wrong with that, it only indicates that there is some connection working between the battery plus pole to the alternator. Because the alternator's internal resistance (apart from some diodes) isn't infinite, you'd expect some positive (with respect to battery's minus) voltage on the ground of the alternator.

I'd 'pimp' my electronics knowledge if I were you, or get some car electrician working on it.

good luck, shakiro

it says the ground is connected, not that its proper. You need to check the resistance, or voltage drop when its loaded.

You could have a blown fuseable link if you are not seeing power in the power distribution center underhood. but it depends on which part of the PDC you are touching, the whole thing wont always be powered.

If you get voltage when the negative side of the batter is disconnected then you probably have an extremely dirty battery and the post is grounding through the impurities on the surface, or you have another power source in your car backfeeding into the wiring. Likely a clock or radio with a battery it it and it has somehow gone bad. This is hard to believe though.

Well the car was off when you did this test right!?

Looks like a bad battery. You are not running the car without the battery installed I hope.

TOP POST

I had an experience where the alternator was actually draining the battery due to some kind of short. Does the battery light come on? My inclination would be to check the alternator... something internal like maybe the voltage regulator.

snipped-for-privacy@gmail.com wrote:

========== ========== Scott, try this......unhook the Battery + cable from the battery post. Touch one lead of your meter to the unattached Neg cable and the other lead to the unattached Pos cable. Set your meter to read OHMs beforehand. See if you've got continuity on the two cables.

I'd would highly suspect that the Bat Pos cable has a short to ground and that you ARE going to see continuity on your meter when you do the OHM check.

If this is the case......then unhook the Bat lead on the starter.....and then recheck for resistance on the OHM setting. (you could just unhook the bat pos lead at the starter and see if your meter is giving you Bat voltage using the same test you stated you performed on the altenator case)

any whoooo.......

My first guess..... I would suspect a shorted Starter.....being as you've been having to jump it off to get it to crank. A shorted starter will "drag", or crank over slow. I've seen this fool a lot of folks into replacing batteries. This may not be the location of the short to ground......but it's the most likely, and easiest to check first for you.

I DO NOT......think you have an Altenator concern, you didn't mention anything about a charging, or battery light, being on.

The battery was likely draining due to the Bat Pos feed having a short to ground, and jumping the vehical fooled you into thinking it was the battery. Don't overthink the diagnosis, remember.......KISS....keep it simple stupid. Sometimes we tend to overthink the process and complicate it when it's not complicated at all.

Finally........ If you don't find that the starter is the location of the short to ground......the easiest step to take next is to hook your Bat Pos cable back up, leave the Neg cable unhooked, rig the test light up so it performs like your meter did in your initial altenator case voltage test.........then take fuses out one at a time untill the test light goes out. That should pinpoint the shorted circuit for you.

hopefully helpfull, let us know.

~:~ MarshMonster ~sips his crownroyal......mmmmm.......now that's good stuff~

I'll mention the obvious first in case you overlooked it. Those sidepost battery cables are known for corroding. It's somtimes hard to see because of the rubber boots. If you haven't yet done so I would remove the rubber boots from both battery cables and make sure they are clean.

If you have no power to the terminal block I would would check for a blown fusible link. The wiring diagram I found shows the feed for the ternianl block coming from the alternater. Even if the terminal block had no power it wouldn't cause everything else to be dead.

Nothing strange there at all. You are using the test leads on your meter to complete the circuit. Your meter is showing circuit voltage (battery voltage) as expected.

Before you go any further clean your battery cables at the battery.

This is test will prove nothing. He should see continuity if he performs this test and that would be expected.

If the positive battery battery cable were shorted to ground I would think he would see arcing when the battery was connected.

Not a valid test.

Please explain how a bad starter would cause no power to the rest of the vehicle. He stated that even the dome light won't light.

Yup

Yup

Nope

Given enough Crown Royal and shroom juice....... I suppose a little confusion could be expected. Bob

One problem I have seen on side contact GM type multiple battery cables is corrosion inside the rubber insulation. This may lead to one or more of the cables not receiving full current flow, and perhaps another appearing to be okay.

You can take the rubber insulator off and clean the connections, or just guess and replace the cables.

This is not a certainty, but a sure possibility.

Really?

You're a pretty smart guy when it comes to electronics. What would you measure if there was a 100 ohm resistor between the battery and the negative battery cable?

How much voltage drop would there be across the 100 ohm resistor if you connected a 0.05 ohm starter motor from the positive battery terminal to the negative battery cable?

Answers: 12.56V, 12.56V.

=========== ===========

========== ========== Mike, I stand corrected, and now defer to greater minds.

though...... I would like to argue a few of the points and suggestions that I made, using a primary defense of "failure to properly convey" my intent, for my intent WAS to provide an expediant way to narrow the symptom to a circuit. I feel I under- stand the concept, I jest can't conceptualize the conveyance of the concept when under duress.

however...... I feel the arguement would lead to me being proven an ass and you being proven correct......even if i think that i am. (correct, not an ass.....i know i'm an ass.....no one needs to prove to me that)

so....

oops.

sorry.

hopefully the tests and related suggestions were not performed as there's a possibility it was a waste of time.

and if they were.......

what'd you find?? (OP)

~:~ MarshMonster ~sips his crownroyal and chunks another mushroom in the tea pot~

Given enough Crown Royal and shroom juice......I could end world hunger, all wars, bigotry, hatred, closed borders, insider trading, the drug trade, and the republican/democrat farse of government rule.............

Given enough Crown Royal and shroom juice....I suppose I could convince the peoples of this earth that the ONE they believe in that exists out in the cosmos would jest be content to be refered to by one common handle..... and God would do if that's all they could come up with......but if they'd like to take a vote on it....he'd settle on jest about any ole name as long as they followed his rules and his word.

yep....... I think.. Given enough Crown Royal and shroom juice......I suppose a little confusion could be expected.

~:~ marsh ~sips his shroom juice.....turns the TV to CNN and ponders............. the world is on shrooms.......~

======== ======== clifto wrote:

========== ========== Well alrighty then........

I'm not so sure how smart Scott is......but you've dang sure proven that you're capable of impressing yourself.

Now......don't take this personally...... but that post makes you come across...(my take on it)...like a dick.

you know..... out to impress yourself by proving you can impress others.

now....don't take it personally.

I'm only attempting to give some constructive critisism. (did i speell that rite?)

yeah..yeah..i know...you didn't type it that way...it's jest the way i read it.

~:~ MarshMonster ~reaches for his prince albert in a can..........fires one up.......mmmm....now that's good smoke~

Is that your final answer?.. What if a normal 20mA 'memory keep alive' current was being pulled out of the battery before you installed the

100 ohm resistor?

Of course, to be fair I'm assuming you want voltage drop across the resistor measured.. you didn't actually specify where you wanted the voltage read from.

To the OP

Hook up the battery like normal: turn on the headlights; measure voltage from the positive terminal of the battery to the Batt terminal on the alternator. Measure voltage from the alternator housing to the negative terminal of the battery. Measure voltage at the battery terminals

Post the numbers and we'll see what we can do for you.. Without going back and re-reading your post, I suspect a bad connection somewhere.. doing voltage drops is much better than trying to measure resistance.

re: your example.. if battery voltage is 12.56v and you measure 12.56v from positive terminal to engine block then yes, your ground is probably ok AS LONG AS YOU ARE PASSING MEANINGFUL AMPS THROUGH THE CIRCUIT.

re: measuring resistances..

Can your meter accurately measure 0.1 ohms? Is 0.1 ohms an acceptable resistance for a battery cable? Applying Ohms Law, what is the voltage drop with a 200 amp current through that 0.1 ohm resistance?

Bonus Question: after doing all that, is 0.1 ohm an acceptable resistance for a battery cable?

Regards,

Jim

I was only trying to get the guy to think a little more thoroughly about his problem. Sorry I came across that way. But if I've taught him to recognize this as a situation where some measurements can't be trusted, and made him think about which ones can, then I achieved my purpose.

If the resistor was between the battery and the battery terminal, as postulated here by others (i.e. bad connection), he'd measure the same from the positive terminal to the engine block.

Trying to keep things simple, I used his points, positive terminal to the engine block.

Nope. Takes a milliohmmeter. Also, digital meters are specified plus or minus one digit, so if the tenths digit is the last one,

0.1 could read as 0.0 or 0.2 anyway.

Nope.

Given my 0.05 ohm starter motor and zero-resistance connections,

8.37V.

Nope.

So let me make sure I'm understanding you.. we're measuring voltage from battery positive terminal to engine block. We have a 100 ohm resistance in the circuit path from the engine block to battery negative terminal. We are reading 12.56v on the meter.

I'm not sure why we are seeing the voltage on the meter... what's the current in the circuit? What would I measure with a 20mA current?

At least we both agree that attempting to measure resistances in this situation is useless.. with a common DMM. This wasn't directed at you.. it was meant for the people advising him to measure resistance.

I don't know how you arrived at this.. can you show your math?

Jim

0.1 ohm wire, 0.05 ohm starter motor, and battery, all in a series circuit. 200 amps can't flow. The 0.1 ohm wire drops 2/3 of the battery voltage (12.56V) or 8.37V. Figured it was a trick question.

If we managed to get 200A through the 0.1 ohm wire, it would drop

20V.

It really wasn't meant to be a trick question.. I was hoping one of the 'measure resistance' people would calculate it and have an 'Ohhh' moment..

I don't like to see more than a 1v drop on the battery cables during cranking.. 1v is easy to see on a DMM, but it works out to 0.005 ohms resistance (@ 200a), which is impossible to read directly on a common meter.

It wasn't a trick question.. but I was expecting anyone attempting it to use the data provided.. not ignore the current, add to the resistance, and use their own voltage..

You didn't comment on the other part of my response.. the 'positive battery terminal to block voltage reading'.. I'm not sure why you'd see any voltage.. of course it's dependent on current flow, but the voltage drop will occur across the resistance on the ground circuit, which means the voltage drop from B+ to engine ground would be zero. The OP simulated this when he disconnected the negative battery cable.. high resistance on the ground path meant battery voltage on the engine block.

Jim

You could be describing a bad connection in one of the battery cables. If they have aftermarket clamps on them, suspect the clamp to cable connection. Don't forget the cables have 2 ends that get corroded.

There also is a mesh ground strap from the bell housing to the body usually on GM's. When this goes bad, the battery charging can act like you describe also.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >