I think it is about to change my battery..
I have finally finished my TPI swap project to my 87 Camaro.
It was originally a carbed LG4 engine and is now a TPI engine.

Everything seems to be working fine and alternator is also charging.

When I start the car the Voltmeter in the dash is at 13 volts..almost 14..
I turn on the headlights and the voltmeter drops just a little bit...still about 13...

But the biggest problem is when I hit the brake pedal...Then the volt drops down to about 8volts and the idle on engine changes...Of course if the ECM don't get the volts it needs to operate that will mess up.

As soon as I let go the brake pedal the volts jumps up again to about 13 volts..

I tried to measure the Volts on the battery when engine is off...about 12.51volts...After the car has started I measure about 14volts..sometimes a little more...So that means the alternator is charging....

Any ideas??..Battery broken?....

 

have you tried to see how much volts is going to the brake lights? and check the battery when you hit the brakes.... but im not a car person but thats what i would do...

 

Congrats on your swap! That's a heck of a project by no small means.

When you depress the brake pedal, do any of the other interior or exterior lights illuminate? Thinking there may be a battery short to ground somewhere..or a ground not making good connection? How much re-wiring have you done with your conversion project?

 

Thank you very much for that compliment..It is really nice to hear when people give me comments like that.
The swap did work out fine for me..Not so very much to rewire actually because most of the wiring on my TPI harness did work out with the carburettor wiring.

When it comes to the wiring on the lights I havent actually replaced anything...Because that one is seperate from the wiring harness that goes to engine, fuel pump, ECM, etc,etc....
So that connector at the C100 connector should be the same also...

When I hit the pedal I notice the lights are dimming..outside and interiour lights...I think I will go for a battery change because I think my battery is a few years now...I bought the car for about 3 years ago and the same battery is in the car now..So i don't know how many years the battery is..

And in the winter the car hasn't been running because of the swap so I think the battery is saying goodbye...
Don't you agree??

 

Is there an autoparts store or shop nearby that can test the battery? If you have a battery charger, put it on that until it indicates that it has a full charge. If it doesnt hold or take a charge, well.. it's probably history. Otherwise, even an old battery may take a charge but fail under load. Hate to see anyone splurge for parts needlessly. Unless you just want a new battery for peace of mind. I understand that reasoning as well.

Good luck!

PS Not absolutely sure (not looking at a C100 connector schematic) but I've run into minor pin position vairiations when swapping harnesses. You might find that you have battery and or a wire into a wrong position at the bulk head connector. Compare your old harness against the new.

 

if the car is on, the car is running off the alternator, not the battery. A dead battery would affect the car all the time, not just when you hit the brake pedal.

changing the battery wont help anything. The problem is either a poor connection from the alternator to the rest of the electrical system (usually around the battery) or a short in the circuit involved with the brake lights.

The poor connection yields a restriction in current from the alternator. Voltage would read fine until you needed more current than the alternator is able to provide (due to the bad connection) so then the voltage drops as you are now sapping battery juice. The battery would be getting little to no charging done as well. So you'll notice that starts get harder and harder, despite normal voltage once the car is started. You'll notice the voltage before you start the car being abnormally low.


If there is a short in the circuit that the brake lights are on and the lights actually come on, then it's only a partial short and it would still have to be less than the inline/underdash fuse can handle. Usually if the fuse is not popping, then you wouldn't be able to pull the alternator voltage down that low, unless it's the wrong fuse for that circuit (too high of a current rating)

I'm putting my money on a loose wire attaching the alternator to the rest of the car. Since the alternator uses the block as it's ground, that leaves the positive cable as the most likely culprit.

 

Of course this is difficult to tell but I don't think it is any poor connections but I may be wrong of course....Car is stalling when I drive very slow with pedal pushed in....

When my car is idling fine in PARK it idles fine...when I hit pedal, it idles poor again because of the ECM...

My starter motor is also rotating engine a little bit slow sometimes because of low voltage...I will test some methods tomorrow and of course try to charge the battery to full again if it is possible...
If not I have to buy a new battery....

And by the way...breaking lights, turning lights, side marker lights tail-lights, headlights, hi beam headlights, backing lights, interiour lights works all fine...Nothing bad with them at all..And that is also because I haven't done anything to the wiring there..Because swapping to TPI only affects the engine harness...The LIGHT harness is a seperate harness so that is like stock....

 

Found out something new today..I have tried several tests on the car and there is something that is not correct..

I found out that the wire I used for activating the alternator was a wire that is in a Circuit with the brake system...So there is 12volt on the wire until i press brake pedal..Then the wire loose the 12v...I don't know what the purple wire is but now I have put in a new wire that is HOT in run so it is activating the alternator all the time...

But still there is some problems with the volts...
I tried to measure the battery today...It is reading about 12.3volts...fully charged over the night...

I started the car and let it run...the volts on battery reads around 14.0V
If I give some throttle the volts are still the same..
Isn't that wrong?..shouldn't the volts raise when RPM is increasing??

Another thing is that the Voltmeter on the dash gauges, jumps very much up and down...When car is idling it is lying around 13V...When I put lights on it goes a lot down...when I use brake lights, turn lights all together it goes almost down to about 9volts...

So there is something that does not work properly...This also affect the ECM so my idle is very rough...

Any more suggestions??...Every GROUND cable should be fine..I checked them today...

 

when the alt is on, it should be around 14v. It might generally drop down to slightly above battery voltage under some circumstances, but for the most part it should be 14.

Having all the lights on and such still shouldn't get you down to 9 volts. Either you have a bad connection still (nothing has to be used to have a bad connection. You could have corrosion or something between contacts around the battery <-> alt circuit). The other option is a strong current draw. This could be normal current and a bad alt, or way more current than it's supposed to be and the alt is fine. A high current ammeter is needed to tell.

 

Ok...Thanks for the response I get from you..It very nice to know people want to help

When it comes to what I have changed on the wiring harness on the swap. I only changed the wiring harness from the C207 connector and the ECM..On the TPI harness there are to places with ground wires on my harness...Both of them grounds to the engine block on the cylinder heads...2 wires come out of the harness (black plastick protection) on each side. Not I am talking backside of the engine close to the distributor...They are good grounded directly to the heads...

The main negative terminal to the battery are grounded on the alternator mounting bracket like it was like stock...There are no corrosion on the battery or any of the places where the ground goes...
As for the light harness there have been no changes at all to the wiring harness...They are all laid up the same as they were before the winter and then they worked perfectly...

My bet here is something about the battery or the alternator or mayby both...I am gonna check tomorrow under the dash close to the ECM if there is any loose wire or something that is not grounded....

What kind of "ammeter" are you talking about???..