Any auto mechanics around?

[hbelkins]

Are there any auto mechanics on the board, either certified or knowledgeable hobbyists that might have access to subscription services or proprietary manufacturer information?

I'm still at a loss on figuring out how to disconnect the hybrid portion of my Saturn Vue Green Line and have it run on the gasoline engine only. Something in the 36-vold hybrid system is preventing the alternator/generator from charging the 12-volt system that runs everything else in the car.

I know it can be done, as someone on one of the Saturn groups I'm in bought a Vue in which the hybrid system had been disconnected before he bought it. I just don't know how to do it.

I'm fairly confident the issue is either with the battery energy control module, a faulty temperature sensor, or the battery itself. All are costly repairs and the mere act of having the issue diagnosed by a GM dealer is prohibitively expensive. Plus, the vehicle would have to be towed to a dealer (it came from the former Saturn dealer in Lexington, but any GM dealership service department should be able to do the work), which could be done free of charge by AAA, but if the price quoted is above my financial means, I'd have to pay to have it towed back home at what would probably cost $4 per loaded mile.

I just need to find someone who can determine how to do it and what I would need to disconnect (or have someone disconnect for me.)

[Dirt Roads]

First off, it looks like there's a lot of bad information floating around on the Internet about your Saturn Vue Hybrid.  So be very careful.  The schematic circuit that I found for the hybrid engine looks like it came off of a typical Saturn internal combustion engine (12-volt schematic).

Secondly, I'm more familiar with old cars, pickups and tractors than newer equipment.  Of course, my vehicle expertise is with modern, high-tech motorized railcars and rubber-tired train (stuff other than locomotives).  That means you should defer to someone with hands-on experience if they show up anywhere.  Anyhow, I should be able to help you diagnose some issues without destroying your car.

Be careful disconnecting 36-volt circuits.  The hot wire better never touch anything grounded.  I'm sensitive to getting shocked from back-EMF on 12-volt circuits, so I have to be extra careful when handling the hot wire on higher DC voltages because you can drop the wire if you get shocked (and with my luck, it will touch something grounded).  Best to handle with an insulated glove.

If you fully disconnect the output from the hybrid charging system you will eventually run down the 36-volt battery.  However, it is likely that the electric hybrid motor is used as a starter and you won't be able to restart your combustion engine once the battery is depleted.  I wouldn't try this unless you have the know-how and equipment to externally charge or jump-start the 36-volt battery.

If you are able to identify the positive 36-volt cable to your electric engine, you can disconnect the hot wire from the electric motor.  You will know real quick if the electric hybrid motor is used as a starter.  If it works as a starter, there are some things we can try to use the 36-volt battery as a jump-start circuit and then disconnect the electric motor.  But this requires some very important safety rules to keep from getting hands chopped off with belts and pulleys and fan blades.  Put the hot wire back on the hybrid electric motor and we'll try that later.

There should be a fuse for the control of the switchover circuit between the 36-volt motor and the combustion engine.  If you can identify this fuse, pull it and see what happens when you start the engine.  If it starts up in ICE mode, you might be safe to run it up-and-down the driveway and see if it hangs in there.  If it starts out in electric mode then it shouldn't switch over to ICE mode and (of course) you'll deplete your 36-volt battery after a while.  See the rule above.

All of this assumes that your car is capable of starting without the 12-volt stuff working properly.  If not, we will need to go down a different path.

[Dirt Roads]

I can't determine what type of charging system your car has.  The charging system for your hybrid could charge your 36-volt battery only or it could be complex enough to charge both the 36-volt battery and the 12-volt battery.  From what you are saying, the hybrid charging system is causing problems with the charging of your 12-volt battery. 

Have you checked all of your fuses? 

With respect to your 12-volt battery, do you have a charger that you can use to get it back up to full charge?   

[Dirt Roads]

Oh, and other than car problems, I hope you had a Happy Easter.

[hbelkins]

The alternator charges both the 12V and 36V systems. The 36V system also charges via regenerative braking. This is known as a "mild hybrid" because the vehicle never runs only on the electrical system the way a Prius does. The hybrid system does two things. It gives a boost during acceleration. It also stops the engine if you are stopped at a red light, and then immediately starts it back when you release the brake.

I do have a charger and used that to charge the battery to start the car yesterday. It will charge the battery up to a full 12 volts.

I had a friend with a scanner read codes in the past. There were some very odd voltage fluctuations noted.

[Dirt Roads]

The alternator charges both the 12V and 36V systems.

It looks like most dual-voltage alternators have a center tap.  Typically, the main hot wire (36 volts) would be red and the middle tap wire (12 volts) would be yellow.  There's a possibility that either the middle tap wire is broken/corroded or the alternator itself is damaged.  There is also the possibility that the diode bank rectifier (or AC/DC converter) for the 12-volt charging circuit is damaged.  And there is also the possibility that the wire from the diode bank (or AC/DC converter) to the positive side of the 12-volt battery is broken/corroded.

Does the alternator have bolts that you can attach a volt-meter onto?  If so, check the taps with a volt-meter on alternating current lowest voltage.  Be careful that you don't get your leads clipped off by belts, pulleys of fan blades when the car is running.  When the car is running, on the alternator taps you should see the 24 volts AC difference between the hot wire and the center tap wire when the car is running and the alternator is functioning.  If so, the alternator is good. 

Some rectifiers let the DC current through to the wrong side.  If so, you can also check for wiring problems without pulling the cables.  Set the volt-meter for direct current lowest voltage.  With the car not running, on the alternator taps you might get 36 volts DC between the hot wire and ground.  If so, you ought to also get 12 volts DC between the middle tap wire and ground.  Some cars have diodes preventing backfeeding through the charging circuits, so it wouldn't surprise me if you get nothing.  But if you (A) have a good alternator; (B) you get 36 volts DC on the alternator when not running; and (C) you don't get 12 volts DC on the alternator when not running then (D) you have isolated the problem between the alternator and the battery.

Let me know if you need help getting a voltmeter with alligator clip leads.

I do have a charger and used that to charge the battery to start the car yesterday. It will charge the battery up to a full 12 volts.

Any idea of how long the car can operate between recharging the 12-volt battery?  This will all depend on how much you use your headlights, blower fans and windows.

[Dirt Roads]

While I'm at it, I have a fair amount of experience with stupid mistakes with what we call "circular voltages" when two battery banks are partially connected.  I also know that GM cars and trucks tend to get this problem when somebody like me tinkers with extra batteries in parallel.  I have a pickup truck where the original owner added an extra 12-volt battery in order to use the truck as a light source for his local outdoor basketball court.  I wasn't thinking, and left all of that in place until it destroyed a couple of batteries and some wiring connectors.  As unbelievable as it may seem, there is also the possibility that the 36-volt battery could be leaking through the 12-volt battery and creating a "circular voltage". 

Another possibility that I've encountered recently is when an automotive computer stays on and drains 5VDC through the ground wires.  Unfortunately, hardly anybody treats the 5-volt ground correctly (that should be a computer frame ground and not the vehicle frame ground).  A constant trickle of very low voltages can burn up a ground strap fairly quickly once corrosion sets in.  By now you should have already checked to see if all of the wires on your 12-volt battery are clean and in good shape.  If not, time to yank them off and hit them with a wire brush.

[abefroman329]

Granted, I owned a 1991 SL1, but this is far more effort than I ever would have put into keeping that car running.