I had the same exact thing happen on my '89 Olds 88. It is the blower control module. Please don't don't confuse this with the resistor or relay, or even the delay module. It is simply called the A/C blower control module, and is usually located under a plastic flap, on the firewall, near the passenger side of the vehicle. I was a parts man at a GM dealership for 18 years and, if my memory serves my correctly, the GM part number will most likely be 12484912. It's not the simplest of operations, but if you have any mechanical ability at all you should be able to do this yourself.
Directly behind the engine, on the middle of the firewall.
My blower would blow cold air at idle & engine would start to overheat, I replaced my thermostat & problem solved.
In the engine compartment. Center of the firewall behind the engine.
It is in the middle of firewall between the engine compartment and the passenger compartment.
The replacement may have been bad. There may also be a problem with the relay from the AC blower to the fuse box.
Replaced many blower modules ( in engine compartment ) from that year. Check it out.
It is on the far right (passenger) side of the engine compartment, attached to the firewall.
on the right side of the engine firewall on a relay brackt. which one?
This likely is a problem with the blower motor module that is within the blower motor unit
Viewed from the engine compartment, the blower motor is behind the engine on the firewall, towards the center of the car. It is usually black and has two larger wires running to it, one purple and one black.
The blower is common to hot and cold air. If it is only cold air that is a problem, then the problem is not the blower motor. The blower motor is actually in the engine compartment, passenger side at the firewall.
Is it the blower motor or is it the fans in the front?if its the fans they will come on at anytime to help cool engine down better.If its the blower motor for the interior heat and air you got a electrical problem. Is it the blower motor or is it the fans in the front?if its the fans they will come on at anytime to help cool engine down better.If its the blower motor for the interior heat and air you got a electrical problem. If it is the blower motor for your heater then it is definatly you blower resistor