My 87 IROC orig had the 305 nd was replaced with a 350 TPI and for a while the fans worked when they were supposed to but all ofa sudden they stopped turning on and off... I replaced the relays ( factory relays were still on the car ) and they still wont turn on... Short of pulling the dual fans off and individually testing the motors ( ie: hot to batt and neg to batt ) im thinking it might be a bad ground. any suggestions?

 

I don't have any suggestions yet, but I'm in the same boat. I swapped the 305 for 350 now none of the heat or air blows except for in the windshield/hot positions. I'm about to go pull the blower motor and check it, but if figure out anything let me know.

 

I'm glad to know I'm not the only one having this sort of issue right now.

I've grounded out the wire running to the fan switch (Using the connector that connects to the fan switch) and the fan seems to work perfect, so I naturally replaced the fan switch with a brand new unit. It still doesn't work. Lucky me.


To the original poster, our cars are different, however I thought from my research that the fan switch in the passenger side cylinder head controls your secondary fan? If so, you can test out it's functionality by removing the connector carefully (as it may be brittle) and grounding it out. If the fan comes on, I would assume that the relay going to it, and the motor itself, are good.

 

As far as your blower motor not sending heat or air, the vaccum line on the heat valve ( if equipped ) is the only way I see of sending heat throughout the car... As for the cooling fans themselves, I gutted the relays and rana simple toggle switch to activate and deactivate them as needed ( takes the not having to worry about it part out of it ) but the car runs much better. I ran the power wires to the two large hot wire ( orange on my car ) I had a smaller white w/ brown stripe wire that had constant power, clipped it, then ran a new ground wire from the fans to the switch, then grounded the switch out using one of the shifter plate mounting bolts ( all hidden under the center console after removing my non working rear hatch switch ) and I havent had a problem with it since