got an 86 trans am 305 4BBL,
ive replaced the heater core and thermostat already, not to sure wat else it can be. the coolant reservoir boils and the electric fans dont turn on. what would be easy ways to isolate the fans and the water pump, or any suggestions that would cause this over heating condition???

 

It may be the fan switch! I had to replace that on my car or have the ac on constantly(my ac isn't hooked up, but the fan still comes on when i turn it on. Once I replaced it, I never had a problem.

 

where would the fan switch be located?? and is there a way for me to test the switch?

 

I'm not sure how to test it, but the switch is on the passenger side of the engine right between the #6 and #8 spark plugs. I just bought one from autozone for around $10 bucks and installed it. I would search around on here for posts about it, and you will find answers. That's how I did!

 

ok i think i know what ur talking about. would that cause the coolant to boil in the reservoir as well or jus the fans not turning on?

 

Well the boiling coolant is the car overheating which would be caused by the fans not coming on.

 

Remove the wire to the fan switch, and with the car turned ON, ground the wire anywhere metal - the fan should run then. If it does, then the switch is bad. If it doesn't, might be the fan relay and not the switch - fan relay should 'click' when that wire is grounded. If relay clicks when car on, but fan doesn't turn, then it's the fan motor itself. Can test fan motor by applying 12v and ground to it's wires.

Also, could be a bad wire between any of those 3 things (switch, relay, motor).