electrical problem: voltage drop
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From: San Bernardino CA
electrical problem: voltage drop maybe its the F-body alternator not cutting the mustard... but here is my deal.
my car shut down on me when i was on the freeway. come to find out the fuel pump quit running because of a voltage drop. i had the fuel pump on, one fan, and my headlights. with only the car idling and the fuel pump running my volt gauge reads about 14. if i click on of of my 2001 f body fans i loose 1 volt. if i then turn on the headlights the fuel pump shuts off and i struggle to maintain 11-12 volts until i turn the headlights off.
my headlights kill the electrical system! they cut my voltage from 14 to 12 by themselves.
my 69 camaro was rewired with a painless 18 circuit chassis harness. im running an optima red top and a painless bank of 3 40amp relays for my cooling fans and fuel pump. im running 2001 f body fans, one is on a manual switch in the car and the other runs off of a 205* thermostat in the cylinder head. my fuel pump is an external edelbrock 120gph.
im running f body accessories and alternator. my alternator does charge however. i have a light bulb wired to the b terminal on the alternator. when i key the ignition it lights up then shuts off when the car is started.
my main concern is: should i get another alternator or should i do something about my headlights? why are they causing such a voltage drop? i can run both my fans and fuel pump with no problems. its the headlights that are killin it.
my car shut down on me when i was on the freeway. come to find out the fuel pump quit running because of a voltage drop. i had the fuel pump on, one fan, and my headlights. with only the car idling and the fuel pump running my volt gauge reads about 14. if i click on of of my 2001 f body fans i loose 1 volt. if i then turn on the headlights the fuel pump shuts off and i struggle to maintain 11-12 volts until i turn the headlights off.
my headlights kill the electrical system! they cut my voltage from 14 to 12 by themselves.
my 69 camaro was rewired with a painless 18 circuit chassis harness. im running an optima red top and a painless bank of 3 40amp relays for my cooling fans and fuel pump. im running 2001 f body fans, one is on a manual switch in the car and the other runs off of a 205* thermostat in the cylinder head. my fuel pump is an external edelbrock 120gph.
im running f body accessories and alternator. my alternator does charge however. i have a light bulb wired to the b terminal on the alternator. when i key the ignition it lights up then shuts off when the car is started.
my main concern is: should i get another alternator or should i do something about my headlights? why are they causing such a voltage drop? i can run both my fans and fuel pump with no problems. its the headlights that are killin it.
Is the power wire to the car from the battery or alternator post?
Check the wire from the alternator to the battery and batt to relays see if its getting hot when everything is on, sounds like a wire may be to small.
Check the wire from the alternator to the battery and batt to relays see if its getting hot when everything is on, sounds like a wire may be to small.
Last edited by ryanvv355; Sep 29, 2008 at 12:12 PM.
2nd getting the alt tested under load.
Next check for dirty or loose connections. Make sure all the crimps are tight. Try pulling the connectors off with your hands. Also looked for frayed/shorted wires.
My guess the problem isn't your headlights, but a weak alternator/bad wiring.
You can check the amps being drawn by the headlights by pulling the headlight fuse and sticking an ampmeter across the terminals.
Next check for dirty or loose connections. Make sure all the crimps are tight. Try pulling the connectors off with your hands. Also looked for frayed/shorted wires.
My guess the problem isn't your headlights, but a weak alternator/bad wiring.
You can check the amps being drawn by the headlights by pulling the headlight fuse and sticking an ampmeter across the terminals.
System drop from 14 to 12 is not going to shut the FP off. Did you check the voltage at the pump, when this happens?
Sounds like you have already isolated the problem circuit: The headlites. I'd check alt output at the alt, and at the batt. Should be <1 volt.
Is the batt in the trunk? If so, RyanVV355's idea is where I'd go next:
"Check the wire from the alternator to the battery and batt to relays see if its getting hot when everything is on, sounds like a wire may be to small".
You can't have too many engine, batt, chassis grounds!!
Sounds like you have already isolated the problem circuit: The headlites. I'd check alt output at the alt, and at the batt. Should be <1 volt.
Is the batt in the trunk? If so, RyanVV355's idea is where I'd go next:
"Check the wire from the alternator to the battery and batt to relays see if its getting hot when everything is on, sounds like a wire may be to small".
You can't have too many engine, batt, chassis grounds!!
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could it be not enough chassis grounds? i only have two main grounds. the negative battery cable attached to the block and a small ground wire running from my intake to the wiper motor bolt.
i dont recall this happening when i had my SBC in there, but then again i wasnt running an electric fuel pump either.
also, this is my second alternator. the regulator is the other one crapped out and would not charge.
i dont recall this happening when i had my SBC in there, but then again i wasnt running an electric fuel pump either.
also, this is my second alternator. the regulator is the other one crapped out and would not charge.
could it be not enough chassis grounds? i only have two main grounds. the negative battery cable attached to the block and a small ground wire running from my intake to the wiper motor bolt.
i dont recall this happening when i had my SBC in there, but then again i wasnt running an electric fuel pump either.
also, this is my second alternator. the regulator is the other one crapped out and would not charge.
i dont recall this happening when i had my SBC in there, but then again i wasnt running an electric fuel pump either.
also, this is my second alternator. the regulator is the other one crapped out and would not charge.
how does your alternator output tie into the rest of the system?
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Verdad Gallardo +1 for pop n wood.. most GM cars had two ground's coming from the battery.. the main one to the block and a smaller one right to the body..
What I did was added one more ground from the Battery to the Frame.
I also added extra grounds from the frame to the engine block (using the engine mount bolts and both sides) and one more ground of the back of the head to the firewall of the other head.
What I did was added one more ground from the Battery to the Frame.
I also added extra grounds from the frame to the engine block (using the engine mount bolts and both sides) and one more ground of the back of the head to the firewall of the other head.
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sorry to get back to you guys so late on this one. here is the painless wiring chart i followed when i wired my car.
only things i did different were i ran wire wires 915 and 916 (both 10g) to the 50 amp fuse then i ran the 8g wire to the battery not the starter. wire 960 still connects to the back of the alternator.
i then have a 12v wire run in series with a light bulb taken from an autometer gauge to the b terminal of the alternator.
also my fuse block had two individual wires for both the high and low beams, left and right. i used a repo light harness and spliced everything together. to give more incite i spliced the two light green high beam wires from the fuse block to the single light green wire in my repo harness and also did the same for the tan low beam wires.
only things i did different were i ran wire wires 915 and 916 (both 10g) to the 50 amp fuse then i ran the 8g wire to the battery not the starter. wire 960 still connects to the back of the alternator.
i then have a 12v wire run in series with a light bulb taken from an autometer gauge to the b terminal of the alternator.
also my fuse block had two individual wires for both the high and low beams, left and right. i used a repo light harness and spliced everything together. to give more incite i spliced the two light green high beam wires from the fuse block to the single light green wire in my repo harness and also did the same for the tan low beam wires.
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im still dealing with this issue. I dont think the alternator is putting out the correct amperage. i checked the battery with the car running and got 14.3V, at the alternator 14.3V, fuse block 14.3V, and Im getting 13.8V at the fuel pump.
I assume the headlights are draining the battery and that is what caused the fuel pump to shut off.
Ill exchanging the alternator for another and try that. Dont know how well these autozone pieces work.
what else could it be? the volt gauge in the car only reads 13V while the car is running, barely 12 with i just key the ignition over. In fact I checked the voltage at the fuel pump with the car off and i barely got 11.8V.
I assume the headlights are draining the battery and that is what caused the fuel pump to shut off.
Ill exchanging the alternator for another and try that. Dont know how well these autozone pieces work.
what else could it be? the volt gauge in the car only reads 13V while the car is running, barely 12 with i just key the ignition over. In fact I checked the voltage at the fuel pump with the car off and i barely got 11.8V.
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I'm with everyone else here and think you have a bad ground on your headlamp circuit. The headlamps probably ground to the body and then have to go through that little ground wire on your intake to get to the neg terminal of the battery. Instead of that, it's backfeeding through the fuel pump ground and shutting it off. Run a ground wire to the body and frame from the neg batt terminal and retry. Or just hook a jumper cable to the neg batt terminal and body and retry your headlamps to see if it kills the fuel pump.
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found out the autozone alternator i had on the car failed its amperage test at the auto parts store. I was given another under warranty.
I will add a few more grounds and test it out once again. its a total pain in the *** to pull the alternator on my 69 camaro. i barely have enough room to pull the alternator out. i also have to removed all the bolts and bracket as well. it damn near sits on the frame.
I will add a few more grounds and test it out once again. its a total pain in the *** to pull the alternator on my 69 camaro. i barely have enough room to pull the alternator out. i also have to removed all the bolts and bracket as well. it damn near sits on the frame.
found out the autozone alternator i had on the car failed its amperage test at the auto parts store. I was given another under warranty.
I will add a few more grounds and test it out once again. its a total pain in the *** to pull the alternator on my 69 camaro. i barely have enough room to pull the alternator out. i also have to removed all the bolts and bracket as well. it damn near sits on the frame.
I will add a few more grounds and test it out once again. its a total pain in the *** to pull the alternator on my 69 camaro. i barely have enough room to pull the alternator out. i also have to removed all the bolts and bracket as well. it damn near sits on the frame.
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thanks! i was wondering if i could get some heavy gauge braided grounds from an auto parts store. im going to add one from the battery to the fender/core support, engine to frame, and just to be safe rear frame to trunk floor.
Actually, I'd run the new ground from the back of one of your cylinder heads to the chassis. The way you describe your current engine ground, it's connected to the intake which is not the ideal location.
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i ordered 3 grounding straps from napa. i told the guy i wanted the braided copper kind so he pulls out this monster inch wide aluminum strap that is about a foot long form the back room. I pass on it. he takes out the catalog and looks up the ones im asking for. Perfect. i order 3 and pay. tells me to come back tomorrow and pick them up. when i get them i find out they are all aluminum straps. im a perfectionist about the under hood of my camaro...
so are these worth it or is copper my better bet?
so are these worth it or is copper my better bet?
Either one will work just fine. Only you can decide if you like the looks or not. Regular black insulated primary wire works too and isn't as noticeable.
Like someone may have said if your black battery wire bolts to the block then you can easily ground your engine by running a wire from the battery post to the chassis. That and grounding the harness to the same post will be all the grounds you need.
Like someone may have said if your black battery wire bolts to the block then you can easily ground your engine by running a wire from the battery post to the chassis. That and grounding the harness to the same post will be all the grounds you need.
That sounds strange that you are losing half a volt between the fuel pump and the rest of the system - is that normal?
im still dealing with this issue. I dont think the alternator is putting out the correct amperage. i checked the battery with the car running and got 14.3V, at the alternator 14.3V, fuse block 14.3V, and Im getting 13.8V at the fuel pump.
I assume the headlights are draining the battery and that is what caused the fuel pump to shut off.
Ill exchanging the alternator for another and try that. Dont know how well these autozone pieces work.
what else could it be? the volt gauge in the car only reads 13V while the car is running, barely 12 with i just key the ignition over. In fact I checked the voltage at the fuel pump with the car off and i barely got 11.8V.
I assume the headlights are draining the battery and that is what caused the fuel pump to shut off.
Ill exchanging the alternator for another and try that. Dont know how well these autozone pieces work.
what else could it be? the volt gauge in the car only reads 13V while the car is running, barely 12 with i just key the ignition over. In fact I checked the voltage at the fuel pump with the car off and i barely got 11.8V.
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i added two more grounds. one from the block where the negative terminal is connected to the subframe where the last fuel line clip is located. then another from the negative top post to the core support. With the existing alternator i get 12.4V with the car off and 14.4 with the car running at the battery and at the alternator. votage gauge in the car only reads 13V. I click on the headlights and the voltage gauge in the car dips to 12V but the battery and alternator still hold 14.4V
im going to change the allternator next. I have a new reman from autozone that was tested prior to leaving the store.
Im wondering if these alternators are junk or if the 12V keyed wire with a light bulb wired in series to the B terminal on the alternator is the problem. I was told to use a 1/2 watt 420ohm resistor but they never worked and my cars battery would die. the tiny light bulb got some voltage flowing.
also. I am running a carbed LS1 setup with an MSD ignition box and truck ignition coils.
im going to change the allternator next. I have a new reman from autozone that was tested prior to leaving the store.
Im wondering if these alternators are junk or if the 12V keyed wire with a light bulb wired in series to the B terminal on the alternator is the problem. I was told to use a 1/2 watt 420ohm resistor but they never worked and my cars battery would die. the tiny light bulb got some voltage flowing.
also. I am running a carbed LS1 setup with an MSD ignition box and truck ignition coils.