High Pitched Squeal at Low RPM's/High Voltage
#1
03-18-2008, 04:55 PM
High Pitched Squeal at Low RPM's/High Voltage
I have a 2002 Mazda Protege ES (2.0L 5 Speed) and so far I absolutely love it. But since about the beginning of winter a high pitched squeal, similar to worn belt, has been driving me nuts. It usually only starts making the noise when I begin pulling power from the car, such as Heater/Fan on medium to high, or run anything else pulling extra voltage and or amps. The transmittance makes me believe its not a worn timing belt. My only thoughts are that it could be a dieing alternator or the Water Pump/Alternator Belt. I am going to try to check the alternator later on with a multimeter, but any ideas?
#3
03-31-2008, 04:37 PM
RE: High Pitched Squeal at Low RPM's/High Voltage
Fireman- Regarding that and also any AUTO TRANS issues links:
Okay, we're trying to get Emma's first car running better here: I'm not sure about this yet, but today I did pull the alternator and took it to a good auto electric shop. He said it tested out well in all areas, but that it was generating too much power, about 16 1/2 volts. He feels that the loud squealing that we had was NOT due to bad shaft bearings (the pulley was very hot) but the fact that the alternator was so hard to spin--simply because it was trying to generate so much electricity--that the fairly new belt was slipping. This diagnosis does make a lot of sense. Some seem to notice more squealing when electrical equipment is on, and that would fit this hypothesis.
There is no voltage regulator attached to this alternator and instead output is controlled by some computer system (control module?). I am told that one way to test this on the car is to pull off the plug from the alternator with the two smaller wires (release clip on outboard side)-- which tells alternator to take a rest--and see if the squealing is gone.
We're also having the somewhat common problems with check engine light on and flashing "OD OFF" light and so can only wonder what incorrect alternator output has done here. The tranny anomalies now are delayed 1-2 upshift and some jarring when going from N to D or R.
Not sure if there is a direct link but the bulk of the tranny problems reported here seem electronic and not mechanical. We are doing a lot of research before we take it to the shop for that part.
This alternator storymakes so much sense that I'm inclined to think the other posts here about loose belts, wobbly shafts and pulleymisalignment are a little off. We've run alternators on millions of cars with belts that were too loose, tight or old--and never had belts frying or jumping off all the time. Cheers, Em's 00 Protege
Okay, we're trying to get Emma's first car running better here: I'm not sure about this yet, but today I did pull the alternator and took it to a good auto electric shop. He said it tested out well in all areas, but that it was generating too much power, about 16 1/2 volts. He feels that the loud squealing that we had was NOT due to bad shaft bearings (the pulley was very hot) but the fact that the alternator was so hard to spin--simply because it was trying to generate so much electricity--that the fairly new belt was slipping. This diagnosis does make a lot of sense. Some seem to notice more squealing when electrical equipment is on, and that would fit this hypothesis.
There is no voltage regulator attached to this alternator and instead output is controlled by some computer system (control module?). I am told that one way to test this on the car is to pull off the plug from the alternator with the two smaller wires (release clip on outboard side)-- which tells alternator to take a rest--and see if the squealing is gone.
We're also having the somewhat common problems with check engine light on and flashing "OD OFF" light and so can only wonder what incorrect alternator output has done here. The tranny anomalies now are delayed 1-2 upshift and some jarring when going from N to D or R.
Not sure if there is a direct link but the bulk of the tranny problems reported here seem electronic and not mechanical. We are doing a lot of research before we take it to the shop for that part.
This alternator storymakes so much sense that I'm inclined to think the other posts here about loose belts, wobbly shafts and pulleymisalignment are a little off. We've run alternators on millions of cars with belts that were too loose, tight or old--and never had belts frying or jumping off all the time. Cheers, Em's 00 Protege
#4
01-02-2012, 12:02 PM
What you say makes sense if it is normal for the alternator to put out 16.5 V on the bench, without a regulator attached.
For what its worth while in the process of searching for a short in my 2001 tribute , I think I damaged the pcm, from disonnecting and reconnecting the pos side of the battery (following directions from a Mazda mechanic), and in turn also subsequently damaged the alternator...
I replaced the alternator and the new one puts out 16.5 V..... unless I pull the fuse to the PCM.. then it goes down to 14.3.
I'm guessing that it is a damaged PCM causing high voltage output, and it needs to be changed before further damage occurs.
good luck
For what its worth while in the process of searching for a short in my 2001 tribute , I think I damaged the pcm, from disonnecting and reconnecting the pos side of the battery (following directions from a Mazda mechanic), and in turn also subsequently damaged the alternator...
I replaced the alternator and the new one puts out 16.5 V..... unless I pull the fuse to the PCM.. then it goes down to 14.3.
I'm guessing that it is a damaged PCM causing high voltage output, and it needs to be changed before further damage occurs.
good luck
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