1988 Suburban, battery won't charge

I've replaced the battery, battery cables, and alternator. I opened up the wire covers and looked at the wires. There is no bare or broken spots, all the wires look good. The suburban will turn over and run just fine, but I only have 2-3 hours of actual run time because the battery (new or old) slowly dies. The voltage reading at the back of the alternator is 12.43 volts with the engine running, and 12.44 volts at the battery with a fresh charge on the battery. With the engine running, the voltage slowly goes down over time and eventually gets low enough that the engine stops. I took the alternator to the local parts house and it checks out good, it passes all tests.

I know the voltage output at the back of the alternator with the engine running should be between 13-15 volts, but it is not. The voltage is normally .01 - .02 volts below the voltage at the battery There is good tension on the belt, and the alternator is turning as expected. Does anyone know of anything else I can check before taking this to a mechanic and have him tell me it's a 5 dollar part and 200 bucks for labor?

--mikew
fort sill, ok

P.S. It's getting kind of old having to carry a spare battery and charge both of my batteries externally every couple of days.

I tried removing the plug from the built in voltage regulator at the back of the alternator. The engine will still start and all the accesories still work. With the voltage regulator connected or disconnected the vehicle performance is still the same. The only problem is it still will not charge and continues to put out 12.41 volts at the back of the alternator and 12.42 at the battery. This shows me the battery is slowly dieing through my time of testing, and the alternator is still not charging.

Based on a schematic and wire colors I can see I need to troubleshoot a few things. Due to money constraints I don't want to go buy a bag of parts and replace everything. By simple process of elimination I can tell that the pink/blk wire going to the distributor and the ignition coil allows the engine to run, so those two big components can't be bad since the engine still runs.

Does any one know ways to test the following parts without buying new ones?

Air controller
Vehicle speed sensor buffer
Air diverter valve
Electronic Vacuum regulator valve
Air select Valve
Air switch
Electronic Vacuum regulator solenoid

--mikew
fort sill, ok

P.S. There is a also new Electronic Controll Module, Fuel Pump Relay, and Fuel Pump in the truck if that's of any help to anyone.

Do you have excite voltage to the alternator? What type alternator? I don't have a good diagram for your alternator circuits.

Do you have a charge lite on the dash, does it work, key on, no crank?

The alternator is a valucraft 105amp remanufactured factory unit I bought from Autozone just a week ago. The voltage at the alternator is consistently .01 volts lower than the battery. After having let it sit for a while and banging on my head with a rusty wrench I went out and checked the voltage again. The voltage is now 12.51 volts at the battery and 12.50 at the alternator.

I don't have a charge light on the dash. The suburban still runs. I can turn on accessories, lights, radio, etc. If I try to start the suburban it fires right up. My only problem is after 2 or 3 hours of actual run time (2 with lights/AC on, 3 with lights off/AC off), the battery charge is so low the suburban will stop running and not have enough juice to start again. That's when I have to take my spare battery and perform a battery swap.

This is extremely frustrating knowing that it will run fine right now, and on Monday or Tuesday I will be swapping out the battery.

--mikew
fort sill, ok

If you have a standard replacement alternator, it won't charge without the excite voltage.Yes, the aftermarket has a one wire self-exciting alternator, I don't believe you have that. If it has the standard L terminal, with the key on, that wire should be hot, if it isn't, the alternator won't charge.

You can go to alternatorparts.com scroll down to alternator repair instructions, then click on the cs 130 link and read the info. I'm sure they can explain it better than I. goodluck

As I stated earlier today "12.51 volts at the battery and 12.50 at the alternator" was my last check of the electronics before I filled the AC and the compressor kicked in. After my last round of tests and checks today, I decided to go ahead and fill the AC with new refridgerant since I had it in my posession and the hood was open. Once I started filling the AC I did notice the compressor was kicking in and the engine idle speed did increase. Blah Blah Blah. I did not check the voltage anywhere before I closed the hood. I just know that I checked the last reading with the engine idling immediately after start up. After having the suburban idling for 15-20 minutes with the front and rear AC blowers running, there should have been a significant drop in voltage.

I read the information on a self exciting alternator at http://www.alternatorparts.com/what_is_a_self_exciting_alternator.htm which is next to the link you suggested. It has the statement "Typically you start the vehicle, rev the motor slightly then alternator starts charging." I was testing prior to engine speed/RPM increasing so I would have seen no improvement all day. I just went out and checked my voltage to the battery at 12.73 volts, which is an improvement on the 12.44volts I started the day with. With the key in the on position the voltage to the L shaped connected was at 12.49volts, and I believe that was the one wire you said should be hot. I don't have the ability to check the same wire for an increase in voltage due to lack of hands/foot for holding a multimeter,connector, ground, and reving the engine.

Overall I see an increase in voltage from start of day untill the end of day after using accessories. Talk about learning something new today.

--mikew
fort sill, ok

Do you have a battery charge light when the ignition key is "on" before you crank it?
The power to excite the alternator goes through this bulb, so if the bulb is broken, the alternator won't excite and so it won't start charging.

Forget the one wire alternator, I don't believe you have that, sorry I brought it up. The other info on that site should be applicable to your alternator.

Do you have a small multi-wire connector at the alternator, how many wires? My info shows, one of those wires should be brown, my info shows that wire should go to the charge indicator. Key on engine off, there should be some voltage on that circuit. If there is nothing there, you need to check the circuit. Like I said before, I'm looking at a cheap diagram.

The plug going into the voltage regulator has 2 wires in it. One wire is brown, and the other is pink w/black stripe. The pink w/black stripe normally has close to the same voltage as the battery. As for the battery charge light I have never noticed one in the last year of owning the vehicle, I never had a need to look as everything ran quite well.

I know I have voltage with the key in the on position on the pink/black wire, and nothing on the brown wire. I would check it now, but unfortunately it is sitting at work in the parking lot with a dead battery, again.

--mikew
Fort Sill, OK

So after replacing the battery (again) with a freshly charged battery, the battery was dead in just 2 miles. I have a tendency to believe there is an open circuit somewhere. I love being stranded at the side of the road. Thank god the Army provided me some good boots and good enough physical conditioning to carry my battery the other 2.5 miles to my home.

I'm about frustrated with this suburban now.

--mikew
fort sill, ok

Is there any possible way to bypass this "excite wire" setup so that once the engine is running the alternator is charging the battery? I drive at very slow speed (normally 20-25mph) at low engine RPM due to local speed limits going to and coming home from work. Only on weekends do I ever get up over 40mph and recently that has only been once every 2-3 weekends.

--mikew
fort sill, ok

I just took apart the dash looking for any bad bulbs, none were bad. All the lights light up. As for indicator lights, from left to right I have "Check Engine", "Fasten Seatbelt", and "Brake". All of the bulbs are good. After putting in a charged battery, I can see that the "Check Engine" light does not turn on during startup, should it? I did notice that the temperature gauge is not functioning either. Is the temp sensor wired into the charging circuit by chance?

--mikew
fort sill, ok

The pink/black wire is the "exciter" voltage from the ign switch. As long as you have batt voltage to that wire with the ign switch on then that circuit is good. The brown wire goes to the instrument panel warning light. But you say that there isn't one that you have seen. So do you have a volt gauge or is the "alt" warning light not working?

If you do have the light system, then I'm inclined to agree with "Borguy" that the Alt needs to see a ground thru that warning light to "excite" the Alt.

The Alt will not charge the batt thru the internal regulator without the 12v "excite" signal or a ground signal (which very well may come thru the warning light).

Another possibility could be the "fusible link" between the Alt and Battery. Follow the red wire from the Alt to probably a junction block. If any part of that wire looks fried, burnt or toasted the "fusible link" needs to be replaced.

You may have a bad ground between the alternator and the battery. An easy way to test this is to take a pair of jumper cables, hook one black to the battery negative and clamp the other side black to the alternator housing

Jeff

I just took apart the dash looking for any bad bulbs, none were bad. All the lights light up. As for indicator lights, from left to right I have "Check Engine", "Fasten Seatbelt", and "Brake". All of the bulbs are good. After putting in a charged battery, I can see that the "Check Engine" light does not turn on during startup, should it? I did notice that the temperature gauge is not functioning either. Is the temp sensor wired into the charging circuit by chance?

--mikew
fort sill, ok

Change the gauges fuse even though it may look good.

777stickman (http://www.automotiveforums.com/vbulletin/member.php?u=134549), I do have voltage gauge built in to the dash. That voltage reading is normally just under 13 volts (center of gauge), which is faily close to the 14.44 - 14.5 volt reading from my multimeter on a freshly charged battery. I took the gauge panel apart today and tested all bulbs, no faulty bulbs. I have traced the red wire from the positive battery post to the alternator. The wire is a straight shot with no other connections in it.

aztecf (http://www.automotiveforums.com/vbulletin/member.php?u=425364)/jeff, I have not yet tried jumper cables from the alternator case to the negative post (if I understood you correctly), please correct me if I am wrong in my understanding. If this is the cause of my problem I'm going to really feel like an idiot for wasting everyones time.

I have posted a picture at http://unixf.com/pics/88_chev_sub_alt_plg.jpg
that way you can see my tests and other questions. Thank you for all the help so far, I greatly appreciate everyones help.

--mikew
fort sill, ok

I changed the fuse, no change. I can't seem to find any jumper cables (that's always my luck too) at the moment to test for a good ground . Look's like I'll trading batteries again for a few more days.

--mikew
fort sill, ok

I hope I didn't miss it in the thread, but I see a lot of discussion regarding battery and alternator voltages. My question is have you or autozone tested this alternator for amperage output? (Don't try this with a common multimeter as most of them only read up to 10A or so.) You should also check to see how much AC voltage is being delivered. Low amperage and AC voltages are signs of defective diode bridges.

AC voltages will not charge your battery and low amperage output can't supply enough current to drive the fan in your ventilation system for long. The battery will power these for a while before it dies.

I have taken the alternator back to Autozone (4 days ago) and it did pass all tests on their diagnostic machine. The sales clerk who helped me did not do a seperate amperes test.

--mikew
fort sill, ok

Everybody has some good ideas.

I was looking at a trade publication, yesterday. It had an alternator section. It said from 86 to the mid 2000s, that the majority of GM alternators used the same pin configuration in the connector. The connector may be rectangular or oval, but the pin layout should be the same, not all, but the majority. The terminals should be labeled P-L-I-S or P-L-F-I, may be hard to see. On these type alternators, it should work fine with only the L-terminal going to the connector. On these type alternators the L, excite, terminal is always next to the P terminals.

If the only problem is excite voltage, you can run a new wire to the L terminal, come off ignition voltage, use a resistor in the circuit, trying to use straight battery voltage without a resistor/ load on the circuit isn't a good idea, I believe several different sizes of resistor will work, 500 ohm, is one.
The connection to the L-terminal has to be GOOD or it won't work. The best way, is to use the proper connector and plug straight into the L-terminal. In the past, on different GM models, where I knew there wasn't any excite voltage to alternator, I have tried backprobing the L-terminal at the connector, with a wire and resistor coming off battery voltage, just for a test, it still wouldn't work, I don't think I had a good enough connection.

I have an 88 chevy work car in the drive, no charge lite, but a volt-meter on the dash. Some of the info I posted here came from this months issue of motor magazine, they have a web site, motor.com, I haven't checked to see if this months issue is posted, yet. It is interesting.

I'm sure all you folks know more about vehicles than I, but,To use any information from any web-site like this, you need to know what your doing. I enjoy this web-site, informative and the people are knowledgeable.

The alternator is clearly marked "S L F P", which is kind of mind bogling because it does not match any of the wiring diagrams I have for that year and model of truck/alternator. The alternator does have a warranty on it, so I might just go check my electronics parts bin for a 500ohm resister and some wire. If all I need to do is hit the "L" with a hot wire -500ohms that might make my day, or make me all tingly! I'll give that a shock tomorrow when I have some daylight. Thank you for that suggestion.

--mikew
fort sill, ok

For testing purposes, you can wire the L terminal hot, using a resistor in the circuit, but don't leave it that way. If you have to wire a new circuit, come off ignition voltage, that way the circuit is only hot, with the key in the on/run position. When the key is off the circuit is dead.

I don't have a wiring diagram for the excite circuit. The order you listed the letters, is not what my info shows. It may not make a difference. On GM alternators, I've never seen it where the L terminal was anything but the excite terminal. You have to make sure the problem is the excite voltage and not something else. My info has to be general in nature, because I can't see your alternator from here.

Did you get a chance to look at the article on the motor site?

I finally threw in the towel and decided to use a workaround. Since the "F" wire comes off the iginition and is fused for the volt gauge, I decided to connect that wire to the "L" wire with a light bulb in the circuit for some resistance. The bulb only comes on momentarily between having the key in the on position and having started the engine. Once the engine runs for 2 or 3 seconds the light shuts off and the alternator starts charging. I checked this morning and the battery was at 12.03 volts. With the engine on the battery voltage was consistently at 14.3-14.41 volts. Once I shut the engine off the voltage at the battery was at 12.92 volts. After a day of driving the battery is still holding a charge higher than what I started the day at. This is just a temporary fix so I don't get stranded at the road side. For now it works. Thank you everyone who came up with the suggestions and for all the help. Walking home with a car battery to charge is frustrating.

http://unixf.com/pics/CSSeries_excite_workaround.jpg


--mikew
fort sill, ok

Now that your alternator is back in bussiness, here is another thing :
Do you have a thick wire going from the + at the battery to a junction(box) somewhere (fuse/relaybox, fireboard, ...)?
If so, you can lead a wire from the "S" (Sensor) on the alt. to this junction.
It will help the regulator maintaining a steadier 14.4V.
When there is a surge of power by several users (fans, lights, ...), the voltage drop will be higher at that junction point than at the alternator and/or battery.
With the Sensor at that point, the regulator will react more accurate.

I have a 1988 chevy blazer 2.8l with the exact same problem. Replaced alternator, battery, and battery cables. Need to know where to go next! Does anybody have a wiring diagram for this? Please help.

I have a 1988 chevy blazer 2.8l with the exact same problem. Replaced alternator, battery, and battery cables. Need to know where to go next! Does anybody have a wiring diagram for this? Please help.

This post is old and started by someone else.
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