Summer straphangers are sweating it out on the 1 and C lines.

Commuters who ride those lines are encounter ing more sweltering train cars than other strap hangers because the air conditioners are likelier to break down, subway officials admit.

R32s — 44-year-old cars that run on the C line — are problematic because of their age, NYC Transit spokesman Charles Seaton said. And the R62A cars used on the 1 line and the Grand Central Shuttle have inverter problems, he said.