Do I need a reverse flush on heat system?

I have '99 Jimmy with 53,000 miles on it. I just had the intake manifold gasket replaced because it was leaking. In that process, they replaced the thermostat, flushed the radiator, and put in new coolant. But now I don't have any heat.

Before this was done I had noticed the heat wasn't real hot but figured it was from a loss of coolant. It seemed to be a fluctuating problem, sometimes I'd have heat and sometimes not. And when I'd add some coolant I *think* I had heat again but not entirely sure since I had gotten used to the intermittent presence of it.

I've seen a few posts in this forum about a reverse flush of the heater core. Is this what I need? When the repair shop said they flushed the system they didn't say anything about a "reverse flush". My guess is they just flushed the radiator. Can anyone give some advice on this?

Thanks!

yep, the heater core is probaby plugged and needs to be flushed out, this is pretty common on these.
its easy enough to do yourself, just unhook the hoses and flush both ways with a garden hose until you see it run clear, you'll be surprised how much crap comes out of an already "flushed" system.