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Help! Where to start on an electrical problem...

T

tonybabb

Guest
I've owned my '89 coupe since new and know it pretty well. I have an electrical problem and don't really know where to start looking. here's what's been happening:
A couple of weeks ago the starter began running sluggishly, but only on one turn, normally the engine turns over 3 - 4 times before it fires and one of the turns is sluggish, then it is normal. This problem stopped happening a week or so back.
This evening, driving home in the dark I noticed the instrument cluster lights were flickering when I was cruising on the highway at 2000 rpm, I also noticed the voltage varying rapidly from 13.8 to 14.9 volts, normally it shows about 14.0 on the highway and never goes above 14.6. With the ignition on and engine turned off the voltmeter shows 11.0 volts, normally it shows 12.2 volts in this configuration. I put a voltmeter across the battery terminals at home and it showed 12.5v.
I don't know if this is related but in the past week I've noticed a high pitched whine on the radio that varies with engine speed.
The battery was new about 6 months ago, the alternator was new a couple of years ago.
Could it be a loose connection somewhere, bad relay? I have no idea where to start.
Thanks,
Tony
 
I can already hear GMJunkie saying "Check the ground straps." :L

An intermittent ground can do weird things to electronics. Good luck and welcome to the :CAC

:thumb Jason
 
I can already hear GMJunkie saying "Check the ground straps." :L

An intermittent ground can do weird things to electronics. Good luck and welcome to the :CAC

:thumb Jason
:L:L:L Nope,Thats not exactly what I'd type!!:boogie:boogie:boogie I'd type,"CHECK and CLEAN ALL Grounds"!!!:thumb:thumb:thumb

"CHECK" Meaning : "Take apart and LOOK"!! :thumb
"CLEAN" Meaning : "Make Connections Spotless" Bolts,Eyelets and Grounding Surfaces on Frame or Engine!!:thumb
"ALL" Meaning : Every frigging 1 under the Hood!!:thumb

These would include,Negative Battery Terminal,the 1-2 wires and Ground Strap located behind the Battery about striate below the Brake Booster on the Frame Rail, (Lt Splash Shield,Side Fender,Battery and Battery-Tray Removal will be Necessary!) the Grounds on Frame Rail just below the Headlamps on each side,The Ground Wire or Wires below and just in front of AC Case on Frame!!:thumb

Now for the FUN ones!!!;LOL(And Most Important Ones!!):thumb
Left Rear of Engine 3 bolts up from the bottom on Bell Housing!
This bolt has a stud and nut on it,you will have to remove the Nut and 2-4 Black wires (Depending Year and Model!)and the other end of the Ground Strap under the Brake Booster!! (You will have to move a few things up top and fish the 2-4 Black wires up to the top to be able to Clean or Replace the eyelets on these wires!!):hb:hb:hb
You will also need to remove and CLEAN this stud from the back of the engine!! It will require a Very Long Extension and Deep Well Wobble Socket to remove and replace!! (There is NO WAY to get your hands up there,you can just barley see it!!):D:D:D

NOTE!! Be sure you don't Loose 1 of the Black wires and not get them back on the stud!!!:hb
http://www.corvetteactioncenter.com/forums/926059-post186.html

While you have the Battery out Clean ALL Fusible link connections on Distribution Block and Positive Battery cable while your there!!:thumb:thumb:thumb

"Bad Grounds make Electronic Components do Weird SH*T"!!:boogie:boogie:boogie

PS Some L98's have Harness Grounds on the Right rear of Block 3 bolts up too!!:thumb



"tonybabb" Welcome to :CAC

I hope this Helps!!:thumb

Happy Vetteing!! :thumb:thumb:thumb

Have a Nice Day!! :D
 
I have a similar problem with my '89 auto. Last night after work it started then died,started again and revved a bit then it idled... Dash lights flicker,amp meter goes between 13.9-15.5v,my heater turned on once,(push button panel style)the numbers on the screen were flickering wildly... If I hit the brakes at idle the car cuts out and dies (very quickly). Couldnt stop at stoplights or the car would die so I managed to time 11 stoplights just right :D !

(Aside from a full tune up its all stock)I just recently replaced the fuel pump,ran great for 56.8 miles started acting up again (still great fp) then a mechanic friend checked it out for me and said I had no spark,check the ignition module which I replaced yesterday... Car ran fine cruising around and getting me to work but 8 hours later the car has issues....

I'll drag her back to the garage and check the every electrical cable gmjunkie suggests but could there be any other areas of interest? With my Firebird being down for a short while I really have to get this fixxed super quick!

Thanks for any help :) .
 
My problem is fixed - mostly

Thanks gmjunkie, great advice and a logical approach to the problem. It turned out that the battery positive terminal was loose (new battery 6 months ago) and there was some of that white powdery gunk between the terminal and the battery post. I cleaned up everything, smeared some dielectric grease and tightened it up, did the negative terminal while I was there and the problem was solved. No flickering dash lights and voltage display back to normal.

My original problem, that had gone away has come back, that is the starter sometimes slows partly when turning the engine over - almost as if the battery is flat but it's not. Could it be the commutator on the starter motor is developing a bad spot? It doesn't happen all the time.

How hard is it to get the starter out? My workshop manual just says to remove it, but I've seen online (I forget where) that you have to remove the exhaust to get at the starter. It's an '89 Auto coupe.

Thanks.

Tony

I have a similar problem with my '89 auto. Last night after work it started then died,started again and revved a bit then it idled... Dash lights flicker,amp meter goes between 13.9-15.5v,my heater turned on once,(push button panel style)the numbers on the screen were flickering wildly... If I hit the brakes at idle the car cuts out and dies (very quickly). Couldnt stop at stoplights or the car would die so I managed to time 11 stoplights just right :D !

(Aside from a full tune up its all stock)I just recently replaced the fuel pump,ran great for 56.8 miles started acting up again (still great fp) then a mechanic friend checked it out for me and said I had no spark,check the ignition module which I replaced yesterday... Car ran fine cruising around and getting me to work but 8 hours later the car has issues....

I'll drag her back to the garage and check the every electrical cable gmjunkie suggests but could there be any other areas of interest? With my Firebird being down for a short while I really have to get this fixxed super quick!

Thanks for any help :) .
 
Thanks gmjunkie, great advice and a logical approach to the problem. It turned out that the battery positive terminal was loose (new battery 6 months ago) and there was some of that white powdery gunk between the terminal and the battery post. I cleaned up everything, smeared some dielectric grease and tightened it up, did the negative terminal while I was there and the problem was solved. No flickering dash lights and voltage display back to normal.

My original problem, that had gone away has come back, that is the starter sometimes slows partly when turning the engine over - almost as if the battery is flat but it's not. Could it be the commutator on the starter motor is developing a bad spot? It doesn't happen all the time.

How hard is it to get the starter out? My workshop manual just says to remove it, but I've seen online (I forget where) that you have to remove the exhaust to get at the starter. It's an '89 Auto coupe.

Thanks.

Tony
Maybe the brushes need replaced!;shrug;shrug;shrugI've never had to remove the exaust on a C4 with a L98 or a LT1 to get the starter off!:thumb
 
1985 C4. This is a weird one. After replacing my dead battery with a new one, I came out the next morning and the new battery was dead. I figured that there must be an unknown drain in the system even when the ignition is turned off, so I replaced the new-dead battery with another new battery and installed an "on-off" switch on the negative post like you would use if you had the car in storage or didn't drive it much. That worked fine but then when I started trying to figure out where the drain in the system was originating, I connected an amp/volt meter to the positive side of the battery and the other probe to the "off or dead" side of the "kill" switch. the meter read 12.5V. It should be reading "0" volts with the switch turned off. I did the fuse pull procedure, but pulling each fuse didn't indicate a short in the accessories. I don't think there are any hidden fuses or fuseable links in an 85 model but I could be wrong. The car runs fine with the "kill" switch in the contact position but when everything is turned off, and the "kill" switch turned off it still reads 12.5V with the meter probes, one on the positive post to the battery and one on the "off" side of the "kill" switch. I suspect that a ground wire is bad or maybe even the... I don't know. By the way. Using the "kill" switch is saving the battery from running down but the 12.5V reading is strange. Any ideas?
 
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This is a weird one. I connected an amp/volt meter to the positive side of the battery and the other probe to the "off or dead" side of the "kill" switch. the meter read 12.5V. It should be reading "0" volts with the switch turned off. Using the "kill" switch is saving the battery from running down but the 12.5V reading is strange.

This is not weird, it is normal operation. There are several circuits in our Corvette's that continue to draw power from the battery after the ignition is turned off (radio, ECM). Your normal current drain should be less than 50 mA (0.05 A) (my '84's is 13 mA). Are you sure there are no lights on (glove box, make-up mirror, under hood)? Something in your cigarette lighter? Any buttons stuck (windows, pwr seat)? Does your power antenna work normal?

To measure this current draw, you'll need to disconnect your under-hood lights, so you can have the hood open but the lights off. Close the doors & hatch, so the courtesy lights will go off. Turn ON your kill switch, so the battery is connected. Connect your amp meter to the two terminals of the kill switch, on the 10A range. Wait about 30 sec. for the ECM to "go to sleep". If your courtesy lights are OFF, turn your kill switch OFF. The amp meter will now read your residual current drain.

If the amp meter indicates a very low current drain, flip the kill switch back ON before disconnecting the amp meter or selecting a lower setting on the meter.

Report back here with your results.

:w
 
This is not weird, it is normal operation. There are several circuits in our Corvette's that continue to draw power from the battery after the ignition is turned off (radio, ECM). Your normal current drain should be less than 50 mA (0.05 A) (my '84's is 13 mA). Are you sure there are no lights on (glove box, make-up mirror, under hood)? Something in your cigarette lighter? Any buttons stuck (windows, pwr seat)? Does your power antenna work normal?

To measure this current draw, you'll need to disconnect your under-hood lights, so you can have the hood open but the lights off. Close the doors & hatch, so the courtesy lights will go off. Turn ON your kill switch, so the battery is connected. Connect your amp meter to the two terminals of the kill switch, on the 10A range. Wait about 30 sec. for the ECM to "go to sleep". If your courtesy lights are OFF, turn your kill switch OFF. The amp meter will now read your residual current drain.

If the amp meter indicates a very low current drain, flip the kill switch back ON before disconnecting the amp meter or selecting a lower setting on the meter.

Report back here with your results.

:w


First, please allow me to apologize for my missed description of how I was testing the circuit. I'm sorry if I misled anyone. My first description was unintentionally misleading.
I will describe it accurately this time after having contacted my neighbor who originally showed me what to do. Now here's the accurate description. I have a "kill switch" that I put on the negative post of the battery so that I can turn it off by simply lifting the contact device off of one end of the "kill switch". With the "kill switch" turned off, I used the volt/amp meter to read the voltage from one side the "kill switch" to the other side of the "kill switch". Although the "kill switch" is turned off, I'm getting a voltage reading of 12.5 volts or better. The positive post is not involved in the reading. My neighbor says that this reading indicates that I have a bad ground wire somewhere in the system. So far, this is all I have to go by and I suppose I'll have two do the old lift up the car and trace the negative cables until I find one that is not making good contact. What puzzles me, is the car starts right up if I turn in the "kill switch" and start the car. I would think that a bad ground wire would prevent a complete circuit needed to turn the starter over. That's the part that's weird in my mind. That everything works fine when I turn on the "kill switch" and start the car.
 
Hot Rod Roy. I just checked it with the volt meter. With the "kill switch" "on", it's measuring 0. With the "kill switch" "off" it's measuring 11.5 V.
 
Now you have a dilemma: Who should you believe?

Here's a simple test for you: Two components . . . a battery and a light bulb. Connect the light bulb to the battery and see that the light bulb works. Disconnect one terminal of the light bulb, and the light bulb goes out. Measure the voltage from the battery to the light bulb at the disconnected points. You will find that you are measuring the voltage of the battery! Now, change your meter to measure milliamps (mA). The light bulb will go ON and you will be measuring the current draw of the light bulb!

That's the simplified version of the test I recommended for your Corvette! Your original description was very good!

:w
 
Hot Rod Roy, thanks. I’ll try that tomorrow. I already have the light bulb and probes that I put together to watch the bulb while I pulled fuses. I’ll give it a try.
 
Hot Rod Roy. I tested it the way you described. Light bulb with aligator clips. Connecting it to the positive and negative poles on the battery, the light goes on. Disconnecting the alligator clip from the negative pole and attaching the volt meter to the positive pole and the disconnected end of the light bulb. Meter reads “0”. Same with micro amp reading.
 
Hot Rod Roy. I tested it the way you described. Light bulb with aligator clips. Connecting it to the positive and negative poles on the battery, the light goes on. Disconnecting the alligator clip from the negative pole and attaching the volt meter to the positive pole and the disconnected end of the light bulb. Meter reads “0”. Same with micro amp reading.



Not sure what you are trying to do, but to measure current draw the ammeter or test light needs to be in series with the negative cable, with the positive cable already installed to the battery.

Why are you doing this, is the battery going dead sitting for a few weeks or days?
 
LLC5 I’ll try to condense the information so you don’t have to read a long story.
First night: dead battery. The battery wouldn’t hold a charge. It kept charging at 3 Amps overnight and the charger gauge never went down to its usual 1 Amp.
Installed a new fresh battery. Dead the next morning.
Installed another new fresh battery but this time I put a “kill switch” on the negative pole so that it wouldn’t drain the new battery down.
Neighbor (hot rod mechanic) came over and put a volt meter on the new battery with the “kill switch” in the disconnected “off” position. He put one probe on the “kill switch” where it’s mounted to the negative pole of the battery and he put the other probe on the “dead” side of the “kill switch”. In other words, he read the “kill switch” in the disconnect position and got a reading of 12.5 volts. Said it looks like a “short” in the negative wiring system. What puzzles me is if it’s a “short”, why does everything work when I turn the “kill switch” on. Engine starts, everything works. If there’s a short in the negative wiring system wouldn’t it prevent the circuit from supplying juice to the starter and and everything else?
 
LLC5 I’ll try to condense the information so you don’t have to read a long story.
First night: dead battery. The battery wouldn’t hold a charge. It kept charging at 3 Amps overnight and the charger gauge never went down to its usual 1 Amp.
Installed a new fresh battery. Dead the next morning.
Installed another new fresh battery but this time I put a “kill switch” on the negative pole so that it wouldn’t drain the new battery down.
Neighbor (hot rod mechanic) came over and put a volt meter on the new battery with the “kill switch” in the disconnected “off” position. He put one probe on the “kill switch” where it’s mounted to the negative pole of the battery and he put the other probe on the “dead” side of the “kill switch”. In other words, he read the “kill switch” in the disconnect position and got a reading of 12.5 volts. Said it looks like a “short” in the negative wiring system. What puzzles me is if it’s a “short”, why does everything work when I turn the “kill switch” on. Engine starts, everything works. If there’s a short in the negative wiring system wouldn’t it prevent the circuit from supplying juice to the starter and and everything else?



A dead short (or short) will burn fuses or wires. A completed circuit or "draw" can eventually drain a battery dead over time. To measure parasitic draw, or drain, on a battery it needs to be performed with an ammeter in series with the negative cable, most newer vehicle can tolerate a 35-50 ma draw on the system with a good high RC battery.
 
LLC5, thanks. I’ll look into parasitic draw. By the way, it’s an 85 not a newer one.
 
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LLC5. Test results for parasitic draw:
Sit down, fasten your seat belt. 11 Amps ! Not ma. Amps! It probably takes that many Amps to turn the starter.
 
LLC5. Test results for parasitic draw:
Sit down, fasten your seat belt. 11 Amps ! Not ma. Amps! It probably takes that many Amps to turn the starter.


On good engine 125-200 A can be normal for a starter draw.

11A is a big parasitic draw, aftermarket stereo or alarm come to mind, start disconnecting aftermarket parts if you have any. Disconnect battery fuses 1 at a time and see which fuse the draw is on. You may want to disconnect your alternator also and see if the drain is gone. Truthfully with an 11A draw you should be getting a spark when the negative cable is attached, tap the cable on and off and see if you can hear any clicking or abnormal noises when the cable is attached and follow any noises to their source.
 
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LLC5. You may have hit it on the head. I have an aftermarket amplifier AND the other day, I set up the car to test the alarm (unrelated to the current detective work) and when I triggered the alarm, it didn’t sound off (horn). I’ll check those two items first then find out if there are any hidden fuses in the car that aren’t listed in the manual. Thanks for the advice.
 

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