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Alternator question

1

1984C4

Guest
I have an annoying flickering of all my lights (interior, digital dash and headlights) when the car is running regardless of electrical loading. It is definetly worse at idle. I checked all the grounds and inspected all the cables. I cleaned some of the contacts and this made it a little better. Alternator puts out 14.2 volts consistently so I think the regulator is good. It is the 97 amp model. My question is: has anyone had this problem and found it to be a bad rectifier diode? There are 3 diodes and a capacitor in the alternator and I was wondering if it would be wise to try and change them even if they checked ok with a meter or should I just put a better 108 amp alternator in it? It seems to me a diode may be bad causing the flicker as it is not smoothing out the ac voltage to dc. Sound right? Any suggestions? TIA Mike PS The battery seems fine. It always starts strong.
 

sriat

Well-known member
Joined
Feb 12, 2006
Messages
82
Location
Kansas
Corvette
1984 Bright Red Coupe
I dont think it is an alternator. Sounds like 1 of 2 things.
1. Bad contacts. IE ground, Power connector. I would remove these connections and use some electrical grease and try again.
2. Somthing that is pulling power in pulses to cause flickering. I assume that you do not have a large audio amplifier. So I would check simthing that would be shorting out. However I believe that number one is more likely

Alternators that I have seen go out either stop putting out or the regulator puts out much too many volts or not enough. Never seen flickering.
Just my 2 cents

The difference of 11 amps on alternators isnt going to fix anyting in my opinion. However if it is an alt problem it would fix that!
 
1

1984C4

Guest
Thanks for the reply. I agree a larger rated alternator wont fix the problem but if I'm going to change it anyway I figure lets go with a bigger one. I checked all the grounds and hit them with emory cloth. They were not corroded anyway. Battery cables are good and connections there are clean also. Someone told me this was a common problem with the early 84 alternators. I don't know if it is really true. I just wonder if it is worth throwing a new voltage regulator in it. I'd hate to waste the money and then have to buy an alternator later anyway. Car only has 34K on it which seems too early for an alternator to go out but 22 year old electronics may be leaking to ground. All my electrical equipment works fine so I don't know if anything is really drawing a huge load or not. Anyone else ever have this problem?
 
Joined
Jan 15, 2004
Messages
2,240
Location
Northern Indiana
Corvette
1987 Z52 Black Convertible
I don't think the voltage regulator for the dash lights and what not is on the alternator itself. My alternator is a year old and my dash lights flicker and get brighter and dimmer. The voltage regulators should stand alone from the alternator.

If you are seeing over 14 volts charging on your display then the alternator is fine.
 

sriat

Well-known member
Joined
Feb 12, 2006
Messages
82
Location
Kansas
Corvette
1984 Bright Red Coupe
As for alternator going out, I have an 84 with 47k miles and it went out. Actually the internal regulator went out. It was producing 16-17volts. SO too much. Only at higher rpms. 14-15 at idle(Still high) This was cooking the battery. SO I made the choice to replace the whole thing. Regulator and all (Built in alt) this solve the problem
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
There are actually six diodes in the alternator. A diode trio and the rectifier which I think also has three. GM did change style of alternator somewhere in the 80s and not sure when , the newer style may be diff. I know in 83 they still had the type I am referring to. Usually if a diode goes bad it is open and you lose amperage.If that is the case you would notice the battery going down under heavy use. It is posible that your brushes are getting bad or dirty. Alternators can cause very strange symptoms.You may want to check the connector on the large red wire. The wire at that point sometimes will begin to break or burn.

Glenn
:w
 

MoeJr

Well-known member
Joined
Jun 7, 2002
Messages
797
Location
Londonderry NH USA
Corvette
Vetteless
The 94-97 amp alternator in our 84's is notorious for causing the condition you describe. They have no protection for the circuits inside and omething can easily get out of whack. It is the same alt. I had in my 84 Buick Regal TType. I was always having problems with lights flickering. See if a newer CS-144 alternator will work for you. Rated at 120 amps and a much better unit.
 
1

1984C4

Guest
Thanks for the replys guys. Moe, I have heard that same thging about these alternators recently that you described. I just don't remember where but it was from a site that claims they sell an alternator guaranteed not to do that. I'm wondering if a newer rebuilt unit has this problem solved with upgrades or not.
 
1

1984C4

Guest
For anyone interested or following this thread I'll post an update. I drove the car yesterday and the flickering was back and the voltage varied from 14 to 15 volts. I disconnected the alternator connector and all the flickering stopped and the car ran great just off the battery. I went and picked up a new regulator ($25) from NAPA and a can of electrical contact cleaner. The inside of the alternator was pretty dirty and it looked like there may have been some rubbing between the stator and rotor. I cleaned everything thoroughly and installed the regulator after verifying my diode trio was good with my meter. After putting it all together I noticed the alternator shaft has a slight wobble but could not feel any dragging when turning. I was afraid it may drag when the belt was put back on but I went this far so I figured I would try it. Took it for a 2 hour ride and there was no evidence of any lights or dash display flickering and voltage was initially 13.9 volts for the first 15-20minutes but then steadyed out to 13.5 to 13.6. I'm going to call this a victory for now but with a possible bent shaft or failing bearing it may only be a short lived victory with an alternator replacement in the future but for now I'll take it! Thanks to everyone who provided input. Mike
 

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