Batteries / Alternator Diagnosis Help Please

[PinzVair]

Hello folks - my first problem and first post. I've browsed through some of the threads on here and figured it might be just as useful to poll the audience.

The Story: Today the Pinz had a hard time starting up (like it was cranking in the super super cold). It was however a warm day today (60°F). I drove it about 4 miles down to the Nut n' Bolt shop. When I came out with the goods the MOST it would do is one or two turns and done. Then it wouldn't even light the dash icons. Fortunately my friend was just down the street at his shop and rolled up with a battery conditioner. We let each 12v charge up for about 15 minutes (40 amp charge cycle) each. Once we got em charged up the Pinz started "ok" and idled happily.

As a test we took a VOM to it before charging and got 11.9v across each 12v individually and 23.8v across the series circuit. BEFORE charging we put the VOM on the 24v circuit posts and with the battery cutoff key ON it read 23.8, as soon as I hit the starter button the VOM dropped to DEAD ZERO!

After charging and getting it started we unscrewed the battery cable connecting the two 12v in series and the Pinz died immeadiately, no attempting, no sputtering, no dieseling, nothing. The instant that the terminal was disconnected the truck died.

Any of your thoughts will be greatly appreciated.

[lindenengineering]

What batteries do you have in the truck?
Regular flooded wet cells or AGM's like Optimas?
Dennis
Linden Engineering/Automotive Inc

[PinzVair]

What batteries do you have in the truck?
Regular flooded wet cells or AGM's like Optimas?
Dennis
Linden Engineering/Automotive Inc

Regular flooded wet cells (1000 CA/795 CCA)

[Pinzgauer Pete]

Just take the batteries out charge them completely and then load test them. A fully charged 12v battery will actually put out 12.6 volts when fully charged and nothing connected to it, so your reading of 11.9 indicates your battery is discharged. The next test that must be done to really determine wether a battery is worth keeping is a load test. Some of the larger automotive parts stores have the ability to do a load test but if you put a load of half of the cold cranking amps of the battery for 15 seconds and the volts does not drop below 9.4 then you have a decent battery that still has life. You also want the static voltage to return to within .2 volts of your original static voltage within 15 seconds of releasing the load. goes like this...fully charged check with volt meter is 12.6.....apply 1/2 cold cranking amps rated on battery voltage drops to no less than 9.4 after 15 seconds.....release load voltage rises and should get to 12.4 within 15 seconds.....if all specs are met you have a decent battery. NOTE....these tests are for wet cells only...hope this helps..regards

[PinzVair]

I will definitely run them through a load test. The batteries are new in the sense that they have hardly been used. The date code stamped in the label says Feb 2010... and I'd guess the Pinz was only started a handful of times between then and now.

Another bit of information that occurred to me this morning is the fact that my Dad had labeled the RED negative battery connect with a huge piece of duct tape and "-". I don't know if he did that before or after possibly connecting it all backwards because honestly I would have connected the RED lead to positive as per conventionality of wire colors.

So taking the chance that at some point he may have connected the batteries backwards... any chance that would have maligned something in the charging circuit?

[audiocontr]

Yup, diode in the alternator. Jim L is the smartie pants on this one. Search out "diode"

[Jimm391730]

First check the "Molex" connector where the alternator wires pass throught the air tin. These connections fail due to corrosion; a little TLC will keep good connections (or repaired connections) good for years, but lack of maintenence will result in corroded, loose, or otherwise bad connections.

From your discription it sounds like you have no charging. If you get the batteries recharged soon enough (sounds like you did) then they will probably be OK.

With a voltmeter across both batteries I expect to see 24-25 volts before cranking; 20-22 volts during cranking (less than 20 shows weak batteries), and 26-28 volts at 1000 rpms or above.

[PinzVair]

Ok I got the tin off the engine and got to some checking. Results as follows:

Before starting engine:
Battery 1 @ 12.5v, Battery 2 @ 12v, Batteries in series @ 24.3v.

Engine Running @ Idle
Battery 1 @ 12.2v, Battery 2 @ 11.7v, Batteries in series @ 23.9v.

Alternator - Engine @ Idle
I used the bolt head where the ground strap connects the alternator to the block for a ground point.
Ground to Red: 73v (I was shocked so I poked it a few more times), 68.3v, 67.0v
Ground to Yellow: 10v
Ground to Black: 0.3v
Ground to "Blue": 29.2v (I think it was blue)

Molex Plug - Engine @ Idle
I used the same ground point for Neg lead and Pos lead jammed into the side of the Molex that would be accessible with the tin still in place - This was done after I had killed the engine with a battery disconnect and restarted.
Ground to Red: 23.9v
Ground to Yellow: 11.0v
Ground to Black: 23.8v
Ground to Blue: 29.1v
Ground to Green: 23.8v

[PinzVair]

And finally... the video!
http://www.youtube.com/watch?v=a1Uk4811nvc

[PinzVair]

So I'm guessing that the H.Blau (Light Blue) off the alternator is the charging circuit? It appears that Light Blue runs to the back of the battery main switch relay, and to the charging circuit dash light indicator.

[Jimm391730]

Wow, video, what a concept. Just like being there.

My first thought is that the heavy red wire at the alternator (73 volts?) is not connected somewhere down the line; it goes to the white terminal connector block at the passenger edge of the air tin you removed (this is commonly called the "Molex" connector). The terminals in one or both halves of the connector will corrode and disentigrate. I bet that if you probe the corresponding wire on the other side of the Molex that you won't see 73V, only 23v (the battery voltage).

Warning! Electrical stuff follows! If you are squeamish, please leave the room...

Alternators are a current source type of device; they get commanded by the voltage regulator to supply more or less current; the voltage regulator decides if the batteries are low, and tell the alternator to produce more current (to charge them). As the batteries get charged, it takes less and less current to hold them to the correct voltage. Anyway, since the alternator is trying to supply a current (not a voltage) if the output of the alternator is open circuit then the voltage goes very high (higher voltage would normally force more current to flow). So unless the open output of the alternator damaged the rectfiers, it looks like the alternator just can't get it's current out to the batteries, and the Molex is the usual suspect. From your video I would guess that the alternator is probably OK and the Molex connector is the spot to check first. If you use very sharp meter probes you can prick through the insulation of the wire; you would expect close to zero volts (less than 1-2 tenths of a volt, maximum) between the wire on the alternator side of the Molex to the corresponding wire on the distributor side. Of course you need to do this with the engine running to see the voltage difference if the connector(s) are bad.

And make sure that you fully charge both batteries individually once you get the alternator charging them again; if one is down, you will not get it fully charged while overcharging the other one when they are charged in series from the truck alternator. Do this once or twice a year and you will get a longer life out of them. You do not even need to disconnect them from the truck wiring (but you can).

[PinzVair]

Hi Jim. Bring on the electrical stuff! I can take it Don't know if you noticed in my post prior to the video... (I had lost my camera man when I tested the "Molex" connector). But here are the results:

Molex Plug - Engine @ Idle
I grounded the Neg lead to the bolt head where the ground strap is attached from the Alternator. Used the Pos lead in the side of the Molex that would be accessible with the tin still in place - This was done after I had killed the engine by disconnecting the battery, reconnecting it and started up the Pinz anew.
Ground to Red: 23.9v
Ground to Yellow: 11.0v
Ground to Black: 23.8v
Ground to Blue: 29.1v
Ground to Green: 23.8v

By the way: The batteries are just shy of 4 years old with probably minimal use and LONG periods of sitting... like all winter... which lasts for stinking ever in Utah.

[Jimm391730]

Right. But if you are measuring 60-70 volts on the red lead on one side of the Molex (or at the alternator) and only 23.9 volts on the red lead on the other side of the Molex, then there is a lack of connection between the two leads... or the voltage would read the same on both sides.

Unplug it, and unscrew it so you can look in both sides and I bet you be surprised at what you find. I don't know why the connector in this location corrodes like it does, but it sure does often enough. Hint: put some "de-ox" grease (or even standard wheel bearing grease) around the back of the terminals (when you get it fixed), where the wires are crimped in to protect the connectors and wire from the elements.

[PinzVair]

Easy enough as I already have the cover off and seats out. I'll make another video I make the videos for my personal use in analyzing problems after the fact... but they turn out fun so I post them on YouTube for everybody.

[Pinzgauer Pete]

again....this can all be checked with a simple load test...voltage is just one part of the equation..and looking at your voltage specs in both the engine off and engine on I think your readings are low, and yes as Jimm states there are lots of folks out there with corroded pins in the molex connector so you should clean and protect the terminals there while you are in there anyway. I may be inaccurate as to the exact specs on the alternator but if I remember right it puts out 35amps. If you go to your local auto place that has a load tester they can determine with a load on each battery the condition of the battery, it is the only real way to determine the health of the battery..I have seen plenty of batteries that read 12.6 volts at rest and the minute a load is applied drop to 5volts telling you that the battery is (kaput) however if it takes the load and the voltage comes back to almost what you started with in 15 seconds your battery is fine. 11.7 is not a charged battery!!!!once the batteries are ruled out then you can load the system to excite the alternator and see how many amps your alternator is putting out. If you see low alternator output you have a charging issue....if you see really high alternator output you have an issue with the regulator. As far as batteries are concerned the lack of use in a vehicle is the single most harmful thing that can happen to them with the exception of overcharging and is the reason that if a vehicle is not being used for extended periods that we use a trickle charger to keep the batteries from sulfating. A simple but non conclusive test that you can do with your voltmeter is to check the voltage at the battery with the truck running and the alternator excited( all lights and accesories on) it has to read more than 24 volts.......27-28volts is likely since it is trying to replace and compensate for what is being taken.....again looking at your tests I do not see this happening...so you are not charging the batteries but again this test will not determine alternator output issues or battery health..hope this helps..cheers