voltage going through roof

[sneakelman]

need help!!!!
whenever i turn the A/C on in my 88 convertable, the voltage goes 18+. it doesnt happen all the time. only itermittently. i have checked the electrical system 9 ways to sunday and can't find one thing wrong. there are no broken wires, no shorts, no corrosion on the cables. A/C system wiring checks out good as well. i am at wits end. anyone have any goood suggestions????
SNEAK

 

[HTRK-1]

Because your 88 has an internal regulator with diodes, I would suspect that under heavy loads it is breaking down and allowing a certain amount od AC on the line. Knowing the early C4's are notorious for altenator problems, this would be my first replacement. Good luck.

 

[rrubel]

I second the suggestion. I had the exact opposite problem - turn on AC, voltage dropped below 11 intermittantly (also dropped way down while idling). Replaced alternator, all is fine.
[RICHR]

 

[sneakelman]

ok, replaced the alternator.....it does the same ^&*) thing!!!! ARGGGGGG
i'm ready to pull my hair out on this one. i know there is a gremlin in there somewhere, just need some sugestions on where to look for the little sucker and put it outa my misery. LOL
thanks for your replies guys!!!!!
SNEAK

 

[Corvette-Pilot]

Have you measured the voltage at the battery when this happens?
Might be a flukey dash gage ?

 

[vigman]

Answers

1) What kinda alternator did you replace it with ( Delco is the correct answer, not pep boys not Lucas, not partsmaster, not rebuilt)

2) Do the dash lights/ headlights go bright when this happens?

3) As stated before... measure the voltage @ the batt.

4) I will have to check the book.. BUT you MIGHT have a bad output line ( wire ) in the harness that will allow voltage to get to the system...but NOT to the battery.. . That MIGHT be the condition which would allow the 18 volts.. but it's a GUESS at this point.. The Alt output DOES have a fusible link ( down by the starter) which IF intermittant.. would allow a no load on the Alt output..
( read BAD)


Vig~

 

[sneakelman]

VIG,
The replacement is an OEM model. NOT rebuilt.
The headlights do NOT go bright, nor does any other electrical equipment show any abnormal signs.
IF the voltage does not go below 18.0 after ten seconds, the dash will go blank and reset itself.(this is what is causing me to think it may be the fusible link you mentioned)
Havent been able to check the battery voltage during this condition as i am always behind the wheel and i can't get it to happen when it is just idling in the driveway, but the battery voltage checks good and strong when tested.
i'm a novice when it comes to electrical........how can i check the fusible link?
I appreciate your help
SNEAK

 

[Corvette-Pilot]

Havent been able to check the battery voltage during this condition as i am always behind the wheel and i can't get it to happen when it is just idling in the driveway, but the battery voltage checks good and strong when tested.I appreciate your help
SNEAK

Do you have a hand held volt meter?
Keep it in the car so that you can wait until it does happen and check it on the spot.

When it does happen how long does it last?
Does it go away on it's own or do you have to shut down and restart?

Question:
The fuseable link has been mentioned. Isn't it basically as the name implies just a fuse? If it went bad then some systems should be dead. If it is on it's way out?? What is the theory as to it's being a suspect?

Another curious question, if the regulator is internal to the alternator, where else could 18v come from?? If it is wworking properly then there should never be 18v anywhere in the system?? You can't get something for nothing in this case and I don't think there are any step up regulators as everything is 12v.

Many autoparts stores will check your alternator/battery for free. Have you tried this to be sure? Could something else be affecting the new regulator and blowing it?

 

[sneakelman]

ok, had the charging system checked and everything checks out fine. it hasnt done it in a couple of days. but i know that this problem wont just "go away". any more suggestions?
and thanks alot guys for all your help!!!!
SNEAK

 

[sneakelman]

well guys, the saga continues.....here's what i have found recently
the voltage will go 18+ even when the KEY IS OFF!!! according to the gauge.
now, we all know this is impossible.....the battery can't send that much voltage.
so, does anyone know how to check the gauge itself AND the ECM.
thanks for your help guys!!!
SNEAK

 

[Corvette-Pilot]

Does the 84 have only a digital voltage gage?
I would think if it does and it is acting up you might need to have the dash overhauled.

Mind you now, I did NOT, repeat NOT, stay at a Holiday Inn last night !!