Do alternator replacement problems track days per year with a high of 100F or more, median station across states?
Across U.S. states, NHTSA owner complaints about alternator replacement run higher where days per year with a high of 100F or more, median station is higher, after adjusting for the makes sold in each state. This is an association across states, not proof that days per year with a high of 100F or more, median station causes this repair.
State reports of this repair against days per year with a high of 100F or more, median station, one dot per stateEach dot is a state: how much more (or less) than expected this repair is reported there, adjusted for the makes sold in the state, against its days per year with a high of 100F or more, median station
How to read it: Each dot is a state. Further right means more days per year with a high of 100f or more, median station; higher up means more complaints for this repair than expected (1.0 is average). If the dots climb to the right, reports of this repair rise with days per year with a high of 100f or more, median station.
What it shows: States with more days per year with a high of 100f or more, median station tend to sit higher on the chart across 34 states: a pattern in the data, not proof of cause.
Data: NOAA NCEI U.S. Climate Normals 1991-2020 (annual), joined to NHTSA owner complaints, downloaded 2026-10-06 · 34 states. Chart: CalcScrape · calcscrape.com
The 10 states with the most days per year with a high of 100F or more, median station (Arizona, Texas, Oklahoma, California, Nevada, Arkansas, Louisiana, Mississippi, South Carolina, Missouri): reports of this repair run 7% above what the makes sold there would predict, and 8 of 10 are above expected. The 10 with the least (Minnesota, Ohio, Michigan, New York, New Hampshire, Massachusetts, Colorado, Wisconsin, Pennsylvania, Connecticut): 2% above, and 4 of 10 are above expected.
Exceptions: California and Missouri are among the highest in days per year with a high of 100F or more, median station but report below expected; New Hampshire (72% above expected) and Connecticut (57% above expected) are among the lowest but above expected.
Split the states into thirds: the third with the least days per year with a high of 100F or more, median station runs 2% above what the makes sold there would predict, the middle third 4% above, and the third with the most 7% above. It steps up steadily.
For days per year with a high of 100F or more, median station, after allowing for the 1562 comparisons we ran, luck alone would produce a pattern this strong about 1 time in 5. Take out any single state and the days per year with a high of 100F or more, median station pattern still holds.
Weak spot: compare only states with similar residential electricity price and the pattern keeps about 43% of its strength, so part of it may come from residential electricity price instead of days per year with a high of 100F or more, median station.
Days above 100F push batteries, cooling systems, belts, hoses and tires past what ordinary summer heat does.