Help! Jumped to 18 volts, and almost crashed because of it!
Thread Starter
Senior Member
Joined: Oct 2000
Posts: 762
Likes: 0
From: Littleton, CO
Car: 1986 Iroc Camaro
Engine: 305 TPI
Transmission: Th700R4 Jr. Raptor
Help! Jumped to 18 volts, and almost crashed because of it!
Hey all. I have been having odd problems with my car lately. I jacked up the car, and noticed my knock sensor was unplugged, so i plugged it back it.
I also used to have my fan wired to always be on, so i replaced the sensor (by the throttle body, the ECU temperature sensor) and re-connected my knock sensor. My car ran great last night, however, when i drove to work today, my idle was 750 RPM, and as i drove down to work, and parked in a spot, suddenly my car revved up to 2,000 RPMs, and Jumped forward, i almost ran right over the concrete walkway! I jammed on the breaks, and put it in park, which is when i noticed that my Voltage guage was reading over 18 volts!!! Whats going on? Has anyone ever had a problem like this before?
The alternator is a 105 AMP, Chevy standard with a internal regulator. It is less then 8 months old.
I did put in a new sensor, and hooked up my knock sensor too, so i guess i did touch electrical stuff myself, but i don't understand what could be causing this.
Very confused. Please help out, i almost peed myself with happiness because my car ran so good last night, after i got everything hooked up, i hate to have to deal with even more ECU or electrical bull§hit.
Thanks! anything anyone can suggest is welcome!
------------------
1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome
I also used to have my fan wired to always be on, so i replaced the sensor (by the throttle body, the ECU temperature sensor) and re-connected my knock sensor. My car ran great last night, however, when i drove to work today, my idle was 750 RPM, and as i drove down to work, and parked in a spot, suddenly my car revved up to 2,000 RPMs, and Jumped forward, i almost ran right over the concrete walkway! I jammed on the breaks, and put it in park, which is when i noticed that my Voltage guage was reading over 18 volts!!! Whats going on? Has anyone ever had a problem like this before?
The alternator is a 105 AMP, Chevy standard with a internal regulator. It is less then 8 months old.
I did put in a new sensor, and hooked up my knock sensor too, so i guess i did touch electrical stuff myself, but i don't understand what could be causing this.
Very confused. Please help out, i almost peed myself with happiness because my car ran so good last night, after i got everything hooked up, i hate to have to deal with even more ECU or electrical bull§hit.
Thanks! anything anyone can suggest is welcome!
------------------
1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome
Member
Joined: Jul 2000
Posts: 461
Likes: 0
From: Warrenton, VA U.S.A.
I'm not sure I understood you post, but does your car now run fine? What is the voltage now?
If everything is okay, you're very fortunate. I would be afraid that, at a minimum, the ECM would have been destroyed. If not, then GM must have designed a power supply for the input to keep overvoltages (withing reason) from destroying it.
To answer your question, I cannot think of why the voltage suddenly shot up so high just because of the items you said you changed (sensors, etc.).
Presuming that the voltage meter is (was) working okay, and that the voltage was indeed >18 volts, I can only think of two reasons for it doing so.
1. The internal voltage regulator went bad. If this is (was) the case, then I would be even more surprised if it suddenly started working again.
2. The voltage sense wire came loose/off. This is the wire that connects to the alternator on the plug with two wires in it. The voltage sense wire goes to the battery +12 (at the starter solenoid) on my 1991 Z28. This wire tells the alternator how much voltage to output (hence "voltage sense"). If this wire were to be disconnected (or increase in resistance due to a poor/bad connection), then it would be telling the alternator (voltage regulator) "I don't see enough (any) voltage, produce more". But this is just a guess as I do not know the specifics of the circuit for the CS-130 voltage regulator. I know the voltage regulators that Motorola makes (made) incorporate a circuit in their voltage regulators to shut down all voltage whenever the sense terminal is disconnected from the battery to prevent just such an overvoltage condition. As an aside, I would guess that varing the voltage to this wire (via a potentiometer/voltage reducer) would be a way to adjust the alternator output voltage. I haven't tried it to confirm it though.
My recommendation to you would be to check the sense wire. Look at the black connector on the side of the case of the alternator and be sure that it is attached firmly. Remove it and make sure the individual sockets inside the black socket are clean and not corroded. Then look at the starter solenoid (if your vehicle is connected like mine) and ensure that all the terminals are clean and firmly connected.
The above is only a guess. Perhaps others would have a better idea/guess.
If everything is okay, you're very fortunate. I would be afraid that, at a minimum, the ECM would have been destroyed. If not, then GM must have designed a power supply for the input to keep overvoltages (withing reason) from destroying it.
To answer your question, I cannot think of why the voltage suddenly shot up so high just because of the items you said you changed (sensors, etc.).
Presuming that the voltage meter is (was) working okay, and that the voltage was indeed >18 volts, I can only think of two reasons for it doing so.
1. The internal voltage regulator went bad. If this is (was) the case, then I would be even more surprised if it suddenly started working again.
2. The voltage sense wire came loose/off. This is the wire that connects to the alternator on the plug with two wires in it. The voltage sense wire goes to the battery +12 (at the starter solenoid) on my 1991 Z28. This wire tells the alternator how much voltage to output (hence "voltage sense"). If this wire were to be disconnected (or increase in resistance due to a poor/bad connection), then it would be telling the alternator (voltage regulator) "I don't see enough (any) voltage, produce more". But this is just a guess as I do not know the specifics of the circuit for the CS-130 voltage regulator. I know the voltage regulators that Motorola makes (made) incorporate a circuit in their voltage regulators to shut down all voltage whenever the sense terminal is disconnected from the battery to prevent just such an overvoltage condition. As an aside, I would guess that varing the voltage to this wire (via a potentiometer/voltage reducer) would be a way to adjust the alternator output voltage. I haven't tried it to confirm it though.
My recommendation to you would be to check the sense wire. Look at the black connector on the side of the case of the alternator and be sure that it is attached firmly. Remove it and make sure the individual sockets inside the black socket are clean and not corroded. Then look at the starter solenoid (if your vehicle is connected like mine) and ensure that all the terminals are clean and firmly connected.
The above is only a guess. Perhaps others would have a better idea/guess.
Thread Starter
Senior Member
Joined: Oct 2000
Posts: 762
Likes: 0
From: Littleton, CO
Car: 1986 Iroc Camaro
Engine: 305 TPI
Transmission: Th700R4 Jr. Raptor
Thanks for the quick reply!
I went to start my car later on today, and it wouldn't start. The positive battery cable wasn't totally on, so i tightened it with my hand, and made sure it had a good connection, and the car started right up, with no problems.
I think what happened, was the positive battery cable was disconnected after i hit the speed bump right before i pulled into my spot. And the alternator was the only thing powering my car, so the boltage jumped up way high to ovewr 18 volts.
Im pretty sure this was it. My bad, thanks for replying!
------------------
1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome
I went to start my car later on today, and it wouldn't start. The positive battery cable wasn't totally on, so i tightened it with my hand, and made sure it had a good connection, and the car started right up, with no problems.
I think what happened, was the positive battery cable was disconnected after i hit the speed bump right before i pulled into my spot. And the alternator was the only thing powering my car, so the boltage jumped up way high to ovewr 18 volts.
Im pretty sure this was it. My bad, thanks for replying!
------------------
1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome
Senior Member
Joined: Oct 2000
Posts: 705
Likes: 0
From: Peoria, IL
Car: 1985 Z-28
Engine: a big one
Transmission: 4 spd auto soon to be a 6 speed
i dont think that, that is possible. whenever i lost one of the battery cables on my monte carlo, the car would shut off. the battery is pert of teh circut and the car wont work with out it, i think.
Junior Member
Joined: May 2001
Posts: 13
Likes: 0
From: Richmond, KS, USA
Its possible but I've heard its bad for the computer, probably the 18 volts. this isn't a problem on pre-computer cars. I bought a VW bug once and the guy wanted to keep the battery cause it was new. So I told him no problem, I started the car up, disconected the battery, wrapped the positive cable in a trash bag so the alternator wouldn't short and drove the twenty miles home. You can even roll start older cars without a battery if you have a standard transmission, but do so only in an emergency situation and the odds are not good.
Thread
Thread Starter
Forum
Replies
Last Post
