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Voltmeter Reading high by owenspike
Started on: 12-31-2020 07:23 PM
Replies: 9 (295 views)
Last post by: theogre on 12-16-2022 07:34 PM
owenspike
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Report this Post12-31-2020 07:23 PM Click Here to See the Profile for owenspikeSend a Private Message to owenspikeEdit/Delete MessageReply w/QuoteDirect Link to This Post
My voltmeter on my 86 GT started reading high the other day. It is almost always in the red. I'm assuming it's the voltage regulator on my alternator, but I'm also wondering if it could be my gauge. Would I get a check engine light or something if my battery was being overcharged?
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Report this Post12-31-2020 08:37 PM Click Here to See the Profile for dremuSend a Private Message to dremuEdit/Delete MessageReply w/QuoteDirect Link to This Post
Easy to check with an external voltmeter -- heck, even one of those free-to-$2.99 ones from Harbor Freight should give you an idea of what's going on. Really should have one to work on an old car anyway.

-- A
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owenspike
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Report this Post12-31-2020 08:49 PM Click Here to See the Profile for owenspikeSend a Private Message to owenspikeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by dremu:

Easy to check with an external voltmeter -- heck, even one of those free-to-$2.99 ones from Harbor Freight should give you an idea of what's going on. Really should have one to work on an old car anyway.

-- A


Will do! Thank you!
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theogre
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Report this Post12-31-2020 10:12 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yup, never trust dash gauges.

Check volt at battery. Should see 14-15v w/ engine running.
If too high then wire to alt or alt have problems.

⚠️ Warning: If you see 16 or worse higher shut off engine or high volts can quickly kill many other E-parts.
Take alt to store and let them test. most stores test them free.

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owenspike
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Report this Post01-01-2021 10:49 PM Click Here to See the Profile for owenspikeSend a Private Message to owenspikeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by theogre:

Yup, never trust dash gauges.

Check volt at battery. Should see 14-15v w/ engine running.
If too high then wire to alt or alt have problems.

⚠️ Warning: If you see 16 or worse higher shut off engine or high volts can quickly kill many other E-parts.
Take alt to store and let them test. most stores test them free.



So, at idle it's 15v, but with even a little bit of gas, it goes up to 18. What's most likely the problem?
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Mike in Sydney
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Report this Post01-02-2021 01:40 AM Click Here to See the Profile for Mike in SydneySend a Private Message to Mike in SydneyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Voltage regulator in the alternator is likely shot. You can replace it but I'd opt for buying a new alternator. You may even want to go to a CS130 unit for more amps if you have an aftermarket sound system or other accessories.

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Mike in Sydney

[This message has been edited by Mike in Sydney (edited 12-18-2022).]

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theogre
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Report this Post01-02-2021 12:50 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Check/clean/fix plug to side of alt. Often SI Alt's have crappy connection there and can cause intermittent problems.

If replace the alt then yes upgrade to CS130.

See my Cave, Watt Story, CS Alternator and Rabid-Wombat's CS-130 Conversion for 85-87 V6.
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creaky78
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Report this Post12-16-2022 11:43 AM Click Here to See the Profile for creaky78Send a Private Message to creaky78Edit/Delete MessageReply w/QuoteDirect Link to This Post
Found this post about high reading voltmeter. My '87 voltmeter reads normal, about 14 volts when engine is started, needle pegs about 15 seconds later. Battery voltage remains 14+ volts. Help!
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Dennis LaGrua
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Report this Post12-16-2022 03:34 PM Click Here to See the Profile for Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
As above check connection and read acoss the battery with a VOM. A reading of 14-14.5V at start cold idle is OK but it should return to around 12-12.V at road load. Should be easy to solve.

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theogre
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Report this Post12-16-2022 07:34 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Dash Volt meter often lies because has many connection to the car that have problems.

Dash Meter Pegs could be meter has loose wiring, bad meter or have real problems... Test at the battery is good.
If has real problems w/ high volts then the ECM often trips codes and CEL turn On.

 
quote
Originally posted by Dennis LaGrua:
As above check connection and read acoss the battery with a VOM. A reading of 14-14.5V at start cold idle is OK but it should return to around 12-12.V at road load. Should be easy to solve.
not quite
Meter at Battery and many other places in the engine bay...
~ 14 to 15v max w/ Engine Running
engine off and battery @ full charge should read 12.6 to ~ 13.0

Battery charge can vary depending on many things...
Assume a good battery... 2 big items
when the car driven last. a day or two or a week or more matters. (Because ECM etc use some power 24/7.)
how long the engine runs. Takes some time to charge, more so when have a low charge battery.

If you measure volts in the cabin or front of Fiero... often see lower volts because of iffy wiring and grounds on top of small volt drop in every connection.
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