Blower motor only works on high.

well a few days ago I put new plugs in my burb and accidentally bent the tang over on the heater core housing under the hood, the thing on top with like 3 wires going into it with a plug so I bent the tangs back up put the plug back on and now I do not havelow or medium fan only high any suggestions? oh yeah it is a 88 gmc suburban thanks guys

Sounds like most likely the blower resistor is bad. Confirm that you have power to it from the switch, if you do, replace it.