Can you show us a picture of the plants?

Have they ever produced anything else? (I mean, big peppers.)

It depends on the temp when they set, I started a Red Hab in December, the first round of pods that set in early spring ripened they were the size of a dime or slightly bigger not by much and turned ripe red. The next wave of pods that set, is still green but they normal size for Habanero's this could be what has happened to you.

As DMForcier stated pics always help. Also are they in pots or in the ground? How often do you water and fertlize?

Mark

Here is a picture of the plants. I water daily, once at 7a.m. and once at 2pm. The 2pm one I started recently, thinking with the extreme heat, maybe they need more water.

Here's a sample chile... you can see that it's about 3" long and is beginning to turn red already.

Fertilizer is Arizona's 10-10-10

Any ideas on why the chile peppers are stunted in size?

Thanks.

Being in Phoenix, I would venture to guess maybe it is a heat issue. But That would just be a guess on my part. Did the fruits stop growing in size around the time your temps started busting 100?
Bruce

whenever fruit is small and turns red fast, it is due to the heat. the cooler temps usually brings good fruit crop.