Goodman heat pump not heating

Question

I have an older heat pump ( Goodman model PGB036100-1A REV A). This morning it would come on for about 1 minute then shut off. There is a LED light that blinks 4 times when it shuts off. According to the back of the panel this is indicating that its a problem with the open limit switch. I called a service technician and was told to shut the heat off for a few minutes and then turn it back on. After doing so the heat has not came back on at all, only blowing out cold air. Any suggestions on what the culprit is and what I can do to fix it? The service tech wants $75.00 to come out and look at it plus $75.00 an hour plus parts to fix it, money that I do not have right now.