| Author |
Message |
Dave Silva (Cypress) (208.27.31.198)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 16, 2004 - 8:57 am: | |
i hope no one minds a way off topic question. This board is such a wealth of knowledge in all things and I'm at the end of my rope.
1990 Volvo 240, bought cheap on ebay with bad alternator. New alternator was also bad, third alternator worked and I got 5000 trouble free miles.
Then the alt goes out again, replaced, new one is bad.
These are the symptoms for all four alternators I've had in the car:
- puts out enough juice to run the car at idle with the battery disconnected.
- Intermittantly puts out the right voltage (13.5- 14.5)
- I drove the car with a meter on it and watched it fall, from 13.5 down to 9 volts and the car dies.
- car will idle indefinately but either the increased load of higher RPMs or the increased speed of the alternator make the voltage drop.
I've checked the ground and all the connections.
These are delco-type remanufactured alternators from Advance Auto Parts
I'm, a fair electrician and I can figure this one out with a little guidance.
thanx
Dave |
Stan (24.67.45.35)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 16, 2004 - 9:16 am: | |
My guess would be that the field is not getting the proper exciting voltage. If it has an external regulator, that would be a likely suspect. If it has an internal regulator (Delco one wire type) then I would suspect a bad battery, or voltage drop in the wires between the battery and the alternator. On a 14 year old vehicle, the wires may be coroded inside the insulation from battery acid creeping up the wire. |
gary Stadler (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 16, 2004 - 11:27 am: | |
I once had a similar problem in my Opel GT. Turned out to be a bad crimp on the alternator's output lead that looked perfect but was intermittent with mechanical movement. Every time I replaced the alternator, I'd inadvertantly wiggle it enough to last a few more months.
Also, just for the info, on that same car prior to having the crimp problem, I replaced the alternator with a new one that was "bad". So knowing the new one was new, I replaced the regulator. It too was "bad". It (stupidly) took me three alternators and three regulators to figure out that what was happening was:
Replaced the alternator, but not the old regulator, which WAS bad and blew out the new alternator. Thinking "heck, I guess it's the regulator", I replaced it...but The now-bad new alternator instantly blew out the new regulator, which then burned out the next new alternator I installed, which blew the next regulator!
Only after realizing what I was stupidly doing did I replace them both at once and then all was well, at least until the crimp went bad a few years later.... |
BrianMCI96A3 (65.40.150.96)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 16, 2004 - 11:46 am: | |
Stan makes some good points, I'd certainly want to make sure the wiring was in good shape.
I have seen, in the past, a similar sounding failure in an alternator, when a diode or two goes bad in the diode trio inside the alternator.
But that MIGHT not necessarily be the case this time.
I'd start with correcting any wiring problems, making certain all connections are tight, all wiring is sound and eliminate any corrosion.
While I was doing that, I'd charge the battery up and after it is fully chaged load test it to insure that it's in good condition.
If the symptoms haven't gone away then, it probably is the diode trio, but there is the possibility that loose connections or corroded wiring could have been causing these failures all along.
One other thing to check: make certain that your
engine has good ground straps, one that goes from the engine to the frame, and from the engine to the body... and check the ground cable from the negative post of the battery where it attaches to the frame or engine, insure it is tight and making good contact.
This COULD cause some of what you are seeing.
Brian |
Guy Bouchard (209.162.160.153)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 16, 2004 - 1:27 pm: | |
Don't ever never run a Delco alternator with the battery disconnected-damage to diodes and regulator system.
guy 4905 |
ralph7 (208.155.122.12)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 16, 2004 - 5:08 pm: | |
When you disconnect Battery On ALT. systems it causes extereme voltage variations in system an those diodes get HURT!! Like Guy said look out. My 89 Suby has eaten 2 alt's an I give up it over voltage's over 2500rpm, batt is new, so to much bad on car so when it dies it's junk it has 222,000mi an only cost $300.00 with 159,000 3yrs ago. did want to use as a toad but?? ralph7 |
Peter Aduskevich (Slowslowpete) (67.75.106.182)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 17, 2004 - 1:39 am: | |
I just observed the exact voltages at similiar rpm's . It was a loose fan belt. |
Vern1 (63.164.202.130)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 17, 2004 - 10:09 am: | |
Greetings,
Check the wiring carefully.
I have had two 240s die because the insulation on the wiring harness turned to powder and then shorted out.
A new harness under the hood fixed them both.
Just check the insulation on the wiring harness.
It won't take long to find if this is the problem.
Hope this helps |
JJJ (172.163.192.207)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 18, 2004 - 11:07 am: | |
Yes, Vern,
I had a diesel 760 that had the same wiring problem. The insulation just dissappeared and left bare wires. By the way, that engine was a pain to keep running!
JJJ |
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