first test drive....3500 fiero

[IsaacHayes]

Dunno, they said they need 5v for it to work?? Are you saying you send it 12v to power on?

[merlot566jka]

according to gm specs, there is a 5v turn on on pin f for the alt. so i got a 5v reg and it charges now. with out it the voltage stays around 13.1 v but the battery dies very fast. with the 5v the voltage is around 15v and charges nicely.

went for drive two...the coolant hose thats by the thermostat, thats held in by a bracket on the head, i built my own backet and used a rubber hose, my bracket blew out. so i need to get that rigged up

[Joseph Upson]

Dunno, they said they need 5v for it to work?? Are you saying you send it 12v to power on?

Whatever the stock alternator from the Fiero receives because I used the same wires that connected to it. The diagrams were posted by AJ... in my 3900 thread in the Fiero forum and I didn't see mention of a 5 volt reference. So I wired the terminals according to their function as compared to the Fiero alternator. It hoovers around 13.3 volts according to the datalog which shows a reading below 12 volts when the engine is not running. What I don't like is that my fuel pump voltage is a full volt lower than the alternator output voltage so I'll look into adding a direct hot wire feed to the relay from the battery. The old pump would surge when the blinker was turned on because the ground wire was frayed and had a few broken wires so a good ground and good hot wire are important for consistant fuel supply.

[merlot566jka]

try 5v on terminal f, watch the volts shoot up. look at the thread here about lx9 generator, bout 2 weeks ago. has all the details, including the schematics

[Joseph Upson]

try 5v on terminal f, watch the volts shoot up. look at the thread here about lx9 generator, bout 2 weeks ago. has all the details, including the schematics

I'll give it a try but I don't see where it will make a difference in that the alternator would need to have a built in circuit that measures voltage to know the difference between 5v and 12v. Otherwise it appearst that 5volts is all that is necessary to just turn the alternator on. I can't think of any purpose for the alternator itself to measure voltage. I was aware that the PCM has the capability to cycle the alternator on and off in which case it would need to be able to measure voltage to know when to do so. As far as I know now I'm basically using 12v instead 5v to turn it on.

What are you reading your voltage from? according to the 07 diagrams in my thread my alternator is charging at about 50% which is apparently sufficient since the alt light isn't coming on and everything works fine. Also it is apparent from the datalog the regulator is doing its thing because the voltage varies by +/- .1 v even with the rpm increase.

[merlot566jka]

i belive the alt does sense voltage, thats how it regulates??

the ecm cycles on and off the alt, with out the 5v its off. mine is on as long as the engine is in run.

i dont know what would happen if u used the 12v to turn it on, i looked at what gm used to turn it off and on, and thats what i did. i read the voltage from a VOM at the batt, alt and of course the guage. just because the lights not coming on doesnt mean its charging. with out the 5v on mine, the light doesnt come on, but its not charging either, its jsut spinning puting out 13 some odd volts. i think the regulator still works without the 5v signal, but i dont think it charges the batt, if that makes sense. put a heavy load on it and see what happens to the voltage, like lights, a/c blower, rad fan, rear fans, and defroster

[johnnymossville]

In theory a battery is made up of six cells that each produce 2.2v. In a perfect situation this means 6*2.2v = 13.2v. An altenator must charge at no less than .5v more than this or 13.7v minimum to actually charge the battery. Less than 13.7v will not turn the no charge light but it will not charge the battery either. At best you will be lucky to keep up with the needs of the vehicle. This could result in low voltage to the fuel pump or dimming of the lights when the flashers are on.

[merlot566jka]

exactly how i interpet it....hapy new year...me drunk

[Joseph Upson]

I know the regulator reads voltage but I thought from an internal standpoint to regulate output, I figured the on off switch is independent of that circuit and not a good point of reference to determine regulation. On the other hand if the alternator is reading voltage at that point it would make a difference. It seemed to be charging adequately though simply by how all of the equipment works. On the battery alone my power windows crawl when operated however with the engine running they work at normal speed. Then again voltage is to amperage what horsepower is to torque, you can have a high, low combination of the two.

In place of a regulator you can also use resistors to step the voltage down which are simpler and probably more dependable in the long run than a regulator, however it would depend on how much deviation you are allowed from 5 volts before the output is affected. 13.3 volts is 50% duty cycle according to the GM manual so obviously it is not at full capacity, I believe I did see a 14 volt reading a few times while datalogging so their is also a curiousity about whether or not the output is at 50% because the load on it did not require anymore than that considering it was idling and revving in neutral.

If I recall correctly it was AJ... on the Fiero forum that gave me the impression along with the diagrams that it would work like a normal alternator if I wired it that way and he's a GM Master tech with access to far more GM Knowledge than what I have so who am I to question.

We'll see what happens when 5 volts is applied, I believe you're absolutely right. It's a hefty piece of equipment rated at 125 amps, the pump voltage maybe lower than actual because I didn't solder the sensor wire in and only added it because it's a datalog input and a diagnostic tool in the event of a no start.

[merlot566jka]

back on track.....weeeeeeeee

[Joseph Upson]

back on track.....weeeeeeeee

That can't be good, especially not with aluminum heads. I remember you talking about coolant level and air pockets, I don't know what you have for a filler neck but the first several minutes of running the 3900 I was watching the temp gauge and because I installed my sensor to it in a different location it was seeing some high values due to intermittent covering by coolant.

I hope there's no engine damage.

The datalog info showed the coolant in the cylinder head was well within safe range below 200 deg but the gauge would approach 240 indicating a false reading however the cylinder head sensor is over piston #6 and the gauge sensor is in the coolant exit crossover pipe at the opposite end of the cylinder head so both maybe reading right since the coolant would be hotter at the exit point.

That could be a good thing since it would show hot before the entire cylinder head actually reached the danger point.

[IsaacHayes]

NAWWWZ!!!!! Wait..... that's not nitrous! Hope you got it shut off right away. That's the coolant pipe that goes into the LIM leaking right?

[Joseph Upson]

NAWWWZ!!!!! Wait..... that's not nitrous! Hope you got it shut off right away. That's the coolant pipe that goes into the LIM leaking right?

Leaking! A little on the conservative side don't you think.

[merlot566jka]

lol it was fine, has happened about 5 times now. it just blows out. ive got it fixed now. the temp never got above 220, so its all gravy.

for a filler neck, ive got the heater out tube cut off with a piece of hose on there. its capped, when i need it i pull the cap and put a funnel in...ill post pics later

[merlot566jka]

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