Buying a used car- problem!

I'm looking at buying a used SUV and have a
problem. When I went to test drive the car
everything looked good but when the car was
moving, the left turn signal did not turn on
immediately, with a few seconds lag time. The right
turn signal functioned fine, and when the car was
stationary, the left turn signal turned on
immediately. The salesman said that he would fix it,
but I'm wondering if this indicates a larger problem
that might be expensive to repair later on.

Thanks in advance for the help!