Im installing a new radiator fan relay on my pops 91 Firebird 5.0 TBI. I know where its located but I cant figure out which one it is because there are two relay switches there. Is it the one on the left or the right, if so what is the other for?

One should have a thick red wire and thick black with red stripe wire, and one should have a thick orange wire with a thick black/white stripe wire. The one with the thick red wire and black/red stripe wire is your radiator fan relay (normally on the left, but can't promise anything after ~20 years). On my 88 TBI it was a 1" X 2" oval relay while the other one will be your fuel pump relay, and that one on mine is a 1" X 2" rectangle. Hope this helps.

Radiator fan relay :
Thick red wire
Thick Black/red stripe wire
Smaller tan/white stripe wire
Smaller green/white stripe wire

Fuel pump relay :
Thick orange wire
smaller red wire
Green/white stripe wire
Thick black/white stripe wire
thick tan/white stripe wire

That should clarify it for you. Any other questions feel free to ask!
Jon

Thanks I greatly appreciate the help.

Sorry if this is a really simple question - I open the hood where do I look for these relays .... ??

:-)
thanks, Nick

iroc-z 5.0l TBI, '88

on your right against the firewall between the brake resivore and fender

Fantastic, thanks tonys91rs

Where would I find the Radiator Fan Switch on and 88 305 TBI, Vin E?

In the passenger side head between spark plugs#6 and #8
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