What can cause a 1995 Chevy Blazer to overheat when running air conditioning?

Answer 1

Dexcool is NOT your friend.

Answer 2

Water pump not pumping much, stuck almost closed thermostat.

Answer 3

Fan clutch
Plugged radiator
bad thermostat

Answer 4

Blocked radiator grill
Blocked Cooling system
Low coolant
Hot weather
Old engine

Answer 5

A leaky old cooling system, first thing to test with a pressure tester. You may be in for a load of worms.
It's sure bet that the water pump is weeping and many of the cooling system hoses are badly deteriorated.
On that model year you can see into the radiator to assess the radiator flow while the engine is running.
My 95 made it 30 years before the water pump seal started to leak, pressure test it and find the dribbles.
If there is an electric boost fan in front of the radiator, make sure it turns on, the main fan is engine pulley.
If the engine fan clutch drive pulley refuses to engage, then you have a simple fan clutch issue to repair.

Run the engine up to operating temperature with the radiator cap removed and look for intermittent coolant flow as the engine thermostat cycles while looking for coolant flow through the radiator core. Then shut it off hot and put the cooling system pressure tester on it with some cardboard under it to see the leaks and follow the green ant trail back to the leak source. The most common leak besides the pump would be the heater hose flange fit line on the back of the V6 intake manifold that goes to the heater core in the firewall.

Answer 6

Fan running normal and no leaks.

Answer 7

1. It 25 years old.
2. Extra strain on the engine.
3. Fan not working properly.
4. Lack of details in question.