Alternator is too hot?

Today, at noon, I asked the alternator's point-of-sale to test the battery and alternator. On checking, their equipment passed both alternator and battery. That result was reassuring, but several hours later, after a typical day's driving, the alternator was still very hot after the engine had been shut down for a few minutes.

Tomorrow, after driving, I plan to check the same alternator with a remote-sensing thermometer, so I can have a specific and accurate record of temperature. Then, call the OEM to determine the normal operating temperature range.

My concern is all electrical components face shorter lives when under temperature stress. Some components are designed for high temperature operations, of course.

Yesterday afternoon, I bought the laser-based thermometer, but have not applied it yet.

In case the alternator OEM says the unit operates at normal temperatures, I have another plan-- reinstall the original alternator to see whether any symptoms improve. I did not have any known problem with the original alternator, and that original unit tested okay at O'Reilly's.

Yesterday, the car stalled twice in the hottest part of the day-- 6-8pm-- after an afternoon of waiting at traffic lights and moving slowly through traffic. During each stall, the instrument panel was dark except for VOLT and OIL indicators. In recovery from each event, I made sure the car had stopped, then shifted to PARK to restart the engine, which started easily each time.

Thanks for checking in!

* I have checked 2carpros.com for similar Buick LeSabre behaviors--
https://www.2carpros.com/search?q=buick+lesabre+1998+stalls+in+traffic&key=added&header=yes

Today, I called the OEM, gave him all the symptoms-- but without laser temperatures, which I have not had a chance to check, yet. The customer tech support representative agreed it appears the new alternator might have a defective regulator.
Although I have to disappear for a few days while I complete a computer upgrade project for a customer, I'll be back in touch, soon.

After completion of the computer project, I am back.

With a noontime check of the alternator after an hour of city traffic, using the new laser thermometer, I determined during several scans that the alternator running temperature is 147F. After one hour, with hood raised for ventilation, the temperature drops to 119F.

This temperature value was given to a tech support specialist for O'Reilly alternators, who said 147F sounded normal. The rough rule-of-thumb, he said, is the alternator tends to match engine temperature.

Of course, that ignores the issue of repeated engine stalls during low-speed, rush-hour drive, with many stops, idling at a traffic light. These did not occur before the new alternator.

So, the plan is to continue use of the new alternator, to see whether the stalls return, and then (in either case) replace the new alternator with the original (which O'Reilly already has tested OK). At that point, monitor the old alternator for temperature and any stalls. At least, that is a basis for comparison.

Frankly, I already suspect the new alternator has voltage regulator problems. But a completed diagnostic process helps confirm direction.

Would an in-store alternator test always detect a faulty voltage regulator?

Previously, I had supposed it would, but your answer suggests that it might not. A voltage regulator, like other electrical components, can have intermittent faults.

In which case, that could explain how a new alternator could stall an engine repeatedly, but next morning, after a night of rest, test "flying colors" when I had the point-of-sale store test its own brand.

Your have raised an important question-- awaiting your response.

Predictably, with the arrival of cool fall temperatures, the alternator gremlin went on a vacation, with not even a hint of a problem. I'll let you know if anything changes.

Thanks, Joe, for all your help during the past year!
Merry Christmas and Happy New 2024.

Joe, the alternator gremlin struck again, but this time on a cool day, after only a modest amount of city driving. The gremlin did not return, but I am watchful.

To search for malfunctions, I requested a scan at two local auto parts stores (to provide a check of one scan against the other, with each store using a different scanner brand), but neither scan showed any alternator issue.

However, the scans agreed my engine had other issues--

Scan Issue 1--
Error P0304-- misfire on cylinder 4. In checking this error with my local auto parts store, I was offered a single spark plug for a replacement, but since the old rule is to replace all plugs at the same time, do you recommend I replace all six plugs? (Of course, I can diagnose with only a single plug to determine whether it makes a difference.)

Scan Issue 2--
Error P0404-- EGR open position performance
Error P1404-- EGR closed position performance
On these errors, I was puzzled, since the EGR valve is indicated both stuck open and stuck closed, Possibly, the valve is so dirty, it will wander slowly between open and closed. A new replacement valve is somewhat expensive, so I would prefer to take the valve assembly apart, and clean it like a dirty carburetor, with carb cleaner spray and small, stiff brush. Will that work? Do you recommend an overnight "soak" in cleaner, and if so, what cleaner?