Mistery Voltage Issue
Thread Starter
Intermediate
Joined: Oct 2013
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From: Memphis TN
Mistery Voltage Issue
Hello everyone,
In 2014 I had my radio rebuilt and outfitted with an Auxiliary cable for my phone/ipod. I don't drive my car very much. A couple years later (2016-ish), the radio popped a capacitor. I removed the radio and sent it back to get repaired. It worked well.
Later, in 2018, my battery exploded. I simply went to start the car and the battery completely exploded, battery acid everywhere. I thought it was a bad battery...
Recently, in 2020, my radio popped the same capacitor. And now my fuel pump is toast.
It's possible these things are all unrelated. What would you do in this situation? I am afraid my alternator is pumping too much juice into the car or maybe I'm missing some sort of resister or regulator that I don't know about.
What do you think?
In 2014 I had my radio rebuilt and outfitted with an Auxiliary cable for my phone/ipod. I don't drive my car very much. A couple years later (2016-ish), the radio popped a capacitor. I removed the radio and sent it back to get repaired. It worked well.
Later, in 2018, my battery exploded. I simply went to start the car and the battery completely exploded, battery acid everywhere. I thought it was a bad battery...
Recently, in 2020, my radio popped the same capacitor. And now my fuel pump is toast.
It's possible these things are all unrelated. What would you do in this situation? I am afraid my alternator is pumping too much juice into the car or maybe I'm missing some sort of resister or regulator that I don't know about.
What do you think?
Le Mans Master
Joined: Jun 2019
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From: Indiana
I had some electrical issues not like yours and the guy who fixed mine ( perfectly too) diagnosed blown capacitors and even scored board..said no way 10 amp fuse did this..sure enough someone put a 30 amp in..
not saying this is your issue but check it out..
here is the guy..not sure who you used..bit the guy is good and very reasonable
https://www.corvetteforum.com/forums...ck-repair.html
also how is your tachometer running?
79 here and alternator can put out up to 15.4volts
edit...se this thread where folks walked me through electrical checks on mine
https://www.corvetteforum.com/forums...-question.html
not saying this is your issue but check it out..
here is the guy..not sure who you used..bit the guy is good and very reasonable
https://www.corvetteforum.com/forums...ck-repair.html
also how is your tachometer running?
79 here and alternator can put out up to 15.4volts
edit...se this thread where folks walked me through electrical checks on mine
https://www.corvetteforum.com/forums...-question.html
Last edited by interpon; May 1, 2021 at 06:47 AM.
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A couple bits of advice. If your not going to list your cars information in your question at least fill in your profile so we can find out what car you have.
Next, have you tryed putting a volt meter on your Battery and rev your engine? Voltage regulator is inside the alternator and is very inexpensive, and or if rebuilding a Alternator is beyond your abilities, simply replace the Alternator or have it rebuilt.
Check your wiring from Alternator to starter solenoid. A voltage drop test would be best.
Best advice if your new to all of this. Go to "Mad electricals" web site. check out there tech pages. excellent write ups on these old cars charging systems and the many ways to improve them.
Next, have you tryed putting a volt meter on your Battery and rev your engine? Voltage regulator is inside the alternator and is very inexpensive, and or if rebuilding a Alternator is beyond your abilities, simply replace the Alternator or have it rebuilt.
Check your wiring from Alternator to starter solenoid. A voltage drop test would be best.
Best advice if your new to all of this. Go to "Mad electricals" web site. check out there tech pages. excellent write ups on these old cars charging systems and the many ways to improve them.
Last edited by 4-vettes; May 1, 2021 at 06:49 AM.
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From: Memphis TN
Le Mans Master
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Sounds like the alternator- which makes AC voltage and then it's converted to DC- is not filtering the AC enough.
A capacitor in the radio -IIRC is rated at 32-50V DC- and will take way more before they blow.
Try connecting a capacitor directly to AC- i know did that as a kid- just like firecrackers!!!
The battery will try to filter out the extra AC ripple- BUT it will cause serious out gassing if too much. It will smell like rotten eggs.
That's the explosion- same reason when you jump start a car- you do not hook the bad battery up last- as it could be outgassing and a spark will set it off.
Another issue- cheap battery tenders are also not filter will- and will send excess AC to the battery- don't know if that was your case.
I'd replace the alternator- sounds like the diodes have broken down in the rectifier.
Richard
A capacitor in the radio -IIRC is rated at 32-50V DC- and will take way more before they blow.
Try connecting a capacitor directly to AC- i know did that as a kid- just like firecrackers!!!
The battery will try to filter out the extra AC ripple- BUT it will cause serious out gassing if too much. It will smell like rotten eggs.
That's the explosion- same reason when you jump start a car- you do not hook the bad battery up last- as it could be outgassing and a spark will set it off.
Another issue- cheap battery tenders are also not filter will- and will send excess AC to the battery- don't know if that was your case.
I'd replace the alternator- sounds like the diodes have broken down in the rectifier.
Richard
Le Mans Master
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From: Memphis TN
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Might I suggest purchasing a voltage gauge that plugs into the cigarette lighter. You can find them on Amazon for less than $20. See what the voltage is reading when the car is running and driving. You really shouldn't be seeing more than say 15 volts, and it should be under 14.5 most of the time.
Ideally - the alternator will produce a relatively nice "steady" DC voltage. As Richard454 stated above - IF you have an alternator producing DC Voltage, but with a lot of higher voltage spikes (caused by failing internal components - or a defective regulator) - that could easily explain your problem. If that's the case - you will most likley see a lot of variation in the voltage readings that a voltage gauge will be reading.
Ideally - the alternator will produce a relatively nice "steady" DC voltage. As Richard454 stated above - IF you have an alternator producing DC Voltage, but with a lot of higher voltage spikes (caused by failing internal components - or a defective regulator) - that could easily explain your problem. If that's the case - you will most likley see a lot of variation in the voltage readings that a voltage gauge will be reading.
Le Mans Master
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68 was the only year on the C3 used outboard regulators (box in picture)- 69(not all GM) and later regulation was done internally.
Might I suggest purchasing a voltage gauge that plugs into the cigarette lighter. You can find them on Amazon for less than $20. See what the voltage is reading when the car is running and driving. You really shouldn't be seeing more than say 15 volts, and it should be under 14.5 most of the time.
Ideally - the alternator will produce a relatively nice "steady" DC voltage. As Richard454 stated above - IF you have an alternator producing DC Voltage, but with a lot of higher voltage spikes (caused by failing internal components - or a defective regulator) - that could easily explain your problem. If that's the case - you will most likley see a lot of variation in the voltage readings that a voltage gauge will be reading.
Ideally - the alternator will produce a relatively nice "steady" DC voltage. As Richard454 stated above - IF you have an alternator producing DC Voltage, but with a lot of higher voltage spikes (caused by failing internal components - or a defective regulator) - that could easily explain your problem. If that's the case - you will most likley see a lot of variation in the voltage readings that a voltage gauge will be reading.
http://www.pvv.org/~syljua/merc/TooSeptST07.pdf
Melting Slicks
Joined: Jul 2005
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Yes- a meter for DC voltage is a great help- but I think he is also seeing AC voltage in his system as well-
http://www.pvv.org/~syljua/merc/TooSeptST07.pdf
I completely agree - hence my comment about "IF you have an alternator producing DC Voltage, but with a lot of higher voltage spikes (caused by failing internal components - or a defective regulator) - that could easily explain your problem. If that's the case - you will most likely see a lot of variation in the voltage readings that a voltage gauge will be reading."
While the best way to see what you're getting out of the Alternator is to hook up a scope and look at the voltage "waveform" - that's not likely something even most shops are capable of. I guess you could look at the alternator output through a blocking cap - to eliminate the DC portion - but again - not many techs would know how to do that.
Last edited by Purple92; May 2, 2021 at 09:03 AM.
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Yes check the voltage regulators, they make a newer version that looks like the old one but is solid state instead of mechanical inside. Or upgrade the alternator to a 10SI or 12SI you would eliminate the external voltage regulator and just need a plug convertor and the external regulator delete adapter. Cheap stuff
Le Mans Master
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You can quickly test for ripple with a DigitalMultimeter set on AC volts. With the engine running at 3,000 rpm and the headlamps on, attach one lead to the alternator B+ terminal and the other to the alternator case. If the AC voltage exceeds .5 volts, you may have a rectification problem. Yes an oscilloscope would provide a even better for diagnosing.