5Volt Reference for alt./ setting?

[Pewter02Camaro]

Is there a way to change the setting for when the 5volt signal for alternator to charge and when to not charge. Ive narrowed my fluctuating voltage when stopping to the 5 volt signal from the pcm. I belive my issue lies here.
new batt., new alt., upgraded big 3. all done less than a week ago. Voltage drops to 12.5 volts when coming to a stop, then climbs back to normal. The car has died numorus times due to this issue. Again i have narrowed it down to the alternator 5volt input signal that tells the alternator to charge. i belive that when i almost come to a stop the pcm is removing the 5 volts causing my problem. All u tuner guys please chime in. Thanks

Jeff

[ssms5411]

Re: 5Volt Reference for alt./ setting?

Even with 2 batteries big 3 upgrade , 200amp ALT. , and caspers voltage booster , mine will idle at 12.2 sometimes then while crusing 13 and WOT is 14.5 around there becuase of the voltage booster. I would say its something else in your system, unless its dropping below 12 volts your system should be working fine. Only time I have seen the computer shut off is when the max 235 degree coolant level is reached and it shuts off the car before it does harm to the engine.

[Rob Bell]

Re: 5Volt Reference for alt./ setting?

So what wire is it that sends this 5v signal? I've always wondered why on earth the voltage drops like that. I've never seen this in any other car. Is this 5v just a signal, or is it actually the current that creates the magnetic field in the windings?

I can see re-wiring this so that the alternator always receives a charge voltage while the car is running.

[Pewter02Camaro]

Re: 5Volt Reference for alt./ setting?

According to my set of GM shop manuals it is the 5 volt on/off wire that the pcm uses to tell the alt to turn on or off. i need to do soem more voltage testing to see if it varys to alter alt. output.

[Rob Bell]

Re: 5Volt Reference for alt./ setting?

I now see this wire as a brown wire labelled "Generator Control" on p. 12-30 of the Haynes Manual. I wonder why the PCM would even turn the alternator on/off? Shouldn't it always be on whenever the engine is running?

I wonder if this can be safely bypassed by running 5v (using a voltage regulator) from a 12v source that is hot when the ignition is on, and that would eliminate the power cutting off.

Now that I think about it, many times I see when I start the car, the voltage is low (12v) and then suddenly kicks up to normal. Now I understand why.

[ssms5411]

Re: 5Volt Reference for alt./ setting?

I wonder if the wire your thinking about, is the wire that powers the PCM. I know I had a wire problem before that my car wouldn't start becuase of the wire for the PCM.

[ssms5411]

Re: 5Volt Reference for alt./ setting?

According to my set of GM shop manuals it is the 5 volt on/off wire that the pcm uses to tell the alt to turn on or off. i need to do soem more voltage testing to see if it varys to alter alt. output.

I think thats what the caspers voltage booster does, it ups the voltage through that wire and TPS signal at 70% and above an extra 1.0-1.2 volts, I know it works as I have my Aeroforce scanner gauge on batt. and coolant all the time for the summer.

[bigbrian442]

Re: 5Volt Reference for alt./ setting?

How low does the RPM drop when you come to a stop?

[darkflare999]

Re: 5Volt Reference for alt./ setting?

where can i get this casper voltage booster booster? and how much is it?...it sounds like i can use that for my system

[ssms5411]

Re: 5Volt Reference for alt./ setting?

where can i get this casper voltage booster booster? and how much is it?...it sounds like i can use that for my system

You have to mod the harness on it for the ALT hook up part, just cutting some plastic off the inside of the harness, I think it was like $80 , just search Caspers Electronics and order the Buick 3800 harness is what I got for my 96' I think 98+ is different wiring or they might have had it listed for a 98+ F-body. But if you have a 93-97 go with the Buick 3800 one. Might want to check with them , I sent them a email with pics on how I got it to work so I hope they could add it to their line up. Just checked your profile a 94 so you might have to go with the Buick one and mod the end harness, I would have to check their site to make sure.

[darkflare999]

Re: 5Volt Reference for alt./ setting?

0ok thanks alot! ill check it out!

[Pewter02Camaro]

Re: 5Volt Reference for alt./ setting?

How low does the RPM drop when you come to a stop?

bout 600 RPM. Car is set to an 800 RPM idle. My nest test is going to be taking it for a short ride withe the belt off the car to see if it does it "the whole RPM/voltage fluctuation" thing taking the carging system out of the equation. I'm starting to wonder if it's a throttlebody issue.

[darkflare999]

Re: 5Volt Reference for alt./ setting?

You have to mod the harness on it for the ALT hook up part, just cutting some plastic off the inside of the harness, I think it was like $80 , just search Caspers Electronics and order the Buick 3800 harness is what I got for my 96' I think 98+ is different wiring or they might have had it listed for a 98+ F-body. But if you have a 93-97 go with the Buick 3800 one. Might want to check with them , I sent them a email with pics on how I got it to work so I hope they could add it to their line up. Just checked your profile a 94 so you might have to go with the Buick one and mod the end harness, I would have to check their site to make sure.

hey ssms i know you said to go with the buick 3800 but i see they have it for 93-97 camaros..whats wrong with this one? http://www.casperselectronics.com/st...roducts_id=668

[ssms5411]

Re: 5Volt Reference for alt./ setting?

They haven't changed it , 93-97 Camaros don't have a round TPS plug -in if you do then it will work, the buick 3800 has the flat sensor to plug in, and you just need to cut a platic piece inside the AlT. plug in so it goes into the other end. I guess they didn't take my advice unless the Buick 3800 has it removed when you get it.

[ssms5411]

Re: 5Volt Reference for alt./ setting?

bout 600 RPM. Car is set to an 800 RPM idle. My nest test is going to be taking it for a short ride withe the belt off the car to see if it does it "the whole RPM/voltage fluctuation" thing taking the carging system out of the equation. I'm starting to wonder if it's a throttlebody issue.

I would up yout idle to 900 RPMS esp. cammed, see how it does then.