Alternator Issue After Rebuild - Please Advise

mca · 08-17-2008, 03:16 PM

I just finished a rebuild and I am having some alternator issues. There were no problems prior to taking the engine out.

Here is the scoop:
The alternator light and OXS lights are on (and BRIGHT) until I hit roughly 2000 RPMs and then both dim out completely as the RPMs increase. Not sure why the OXS light is on again. I just reset it 3000 miles ago. Maybe it came on after hitting 130,000 k miles?

The 101 Projects book (p.62) does not include this scenario in its troubleshooting guidelines. The closest match is when the alternator light is dim to start and then goes out with RPM increase. Mine starts bright, gets dimmer, and eventually goes out (oxy light responds in same fashion).

The voltage with the engine running is around 11.4 and with the engine off it is 12.2. I charged the battery last night and it checked out ok today at the battery store. It is a red top optima just over a year old. Yesterday the battery took a lot of strain and drain due to trying to get the engine started for the first time after the rebuild (I had improperly installed the dizzy). The starter took a lot punishment too.

I checked the tranny ground strap and it is fine, all starter connections are tight, and all of the alternator connections are tight and correct.

Any ideas would be greatly appreciated. Other than the alternator issue the car runs fantastic.

Cheers,
Craig

moanglin · 08-17-2008, 04:37 PM

with the engine running the voltage should be higher i'm thinking around 13.5v or higher i would check the altenator connections and air gap at the rotor for correct clearance. what was the battery voltage at the battery store? 13.5 or higher, the voltage value you gave are to low hope this helps

stevej37 · 08-17-2008, 04:53 PM

Original alternator in car? Sure sounds like the culprit...voltage when running is too low.

mca · 08-17-2008, 05:44 PM

Alternator has about 50k miles on it. I am skeptical that it is the culprit b/c it worked prior to removing the engine 2 weeks ago.

moanglin · 08-18-2008, 07:47 AM

did you inspect the brushes with the engine out, they may be worn,or perhaps the commutator needs cleaning.

Elombard · 08-18-2008, 08:01 AM

Waynes book would cover a bad alternator in this scenario...any chance one of the wires on the back is hooked up wrong??

Any luck getting the other one off?

moanglin · 08-18-2008, 08:19 AM

i don't think that is the problem if you are getting 12.2v output,i would check the brushes and the commutator for a build up of carbon from the wear of the brushes.

Elombard · 08-18-2008, 09:17 AM

You probably know more than I. I was thinking 12.2 could be within error of just reading the battery??

Rot 911 · 08-18-2008, 09:48 AM

Quote:

Originally Posted by mca

The voltage with the engine running is around 11.4 and with the engine off it is 12.2.
Cheers,
Craig

Well it has to be something that changed since the engine was out. Check all wiring. If it has a external voltage regulator check that also. If all of that checks out ok, then you have a bad alternator or regulator.

Brad w · 08-18-2008, 11:09 AM

Funny I ran across this thread. I have the same problem after rebuild and I think I have a wire crossed. I will let you know the outcome.

moanglin · 08-18-2008, 11:25 AM

i am thinking that a fully charged will read at least 13.0v+ to 14.0v have you verified these values? have you checked the other items i mentioned?

mca · 08-18-2008, 11:39 AM

I charged the battery last night.

As soon as I pulled the charger the voltage at the battery read 13+ . I continued to check it every hour and it decreased to 12.6.

This morning it measured at 12.5 and seems to be holding steady. The battery was NOT connected to the car during these tests.

Again, the alternator is properly connected. I am 110% sure of this.

I think that I will pull my alternator and have it bench tested if possible. I will also test the extra alternator that I have if I can get it out of the fan housing.

moanglin · 08-18-2008, 11:52 AM

have the battery load tested at your local parts store to verify that the amp load is correct, have you checked the output at your regulator?

mca · 08-18-2008, 01:42 PM

it was load tested yesterday ... but, if I get home and the voltage has dropped under 12.5 (measured this morning) the battery is going to be replaced.

honestly, i just don't see how the alternator could be bad. and i was very careful with the wiring harness during the rebuild. it wasn't even in bad shape.

moanglin · 08-18-2008, 02:04 PM

all being true did you inspect the brushes these "pick up the voltage and amps that the alt. produces, check the alt for the correct voltage output.

47silver · 47silver's Garage

under 12 v is too low. You alternator has probably given it up.

If you have the time get the one in your car rebuilt as you know it will fit.

I had 2 bad rebuilds finally bought a new one. If i were to do it again i would have waited for pelican.

when re-installing i used emery clothe strips between the fan blade tips and the housing to keep equal distance around the housing. Then when you tighten the nuts the fan should stay true.

I also cut the air shroud so that i could use 3 nuts directly on the fan housing. 2 on the top and one on the bottom in a Y formation. I torgued them to 45 inch pounds.

Tim_in_MD · 08-18-2008, 06:27 PM

I had identical symptoms in terms of battery voltage (didn't have the alternator light on consistently) and it was the alternator. I found with mine that whoever did the previous replacement neglected to attach the larger brown ground wire to the case--probably the reason why the previous rebuilt alt only saw about 30k miles, and why the previous owner had a series of charging problems before essentially parking the car for six years. Replaced the alternator and it charges like a champ.

Anyway, check your connections but I'd bet you a quarter your alternator died.

Brad w · 08-27-2008, 04:54 AM

MCA did you find the source of tour troubles? I have ot touched mine.

mca · 08-27-2008, 06:19 AM

YES!

Drove it today after installing a GOOD alternator and installing the exhaust.

Problem solved.

However, I am waiting to hear how the old alternator tested. Should find out today.

If it tests GOOD ... then my fan belt was too loose. I was running with 2 shims in and 4 out. Changed to 1 in and 5 out - seems too tight now but before it seemed too loose. The whole deflection thing is tough too b/c with enough pressure you can make any belt move 1/4 to 1/2 inch.

I will keep you posted.

Brad w · 08-27-2008, 06:58 AM

Hard to believe that the Alt just dies after taking the engine out. My starter also died and I had to have it rebuilt.
I installed a new wire harness so every time I have a issue I think thats the problem. For instance my alt has the internal regulator but the car was original with a external. So it makes me wonder....
Brad