91 cooling fan question

I am helping a friend try to figure this out. He has a 91 with a 305 and it has two electric cooling fans and when it gets hot( in the red) the fan on the passenger side of the car turns on but not the driver side fan. When you turn on the heater the passenger side does not work but the driver side does. I am wondering if this could be goofy wiring or if it is supposed to be this way because the car runs hot.

i know that the pasenger side fan is controled by a thermostat located on the pasenger-side head right above the #6 cyl. The driver-side fan gets turned on when the a/c is activated. there is a fairly cheap way to get the pasenger side fan to turn on at lower temperature and that is to get an aftermarket thermostat. i saw some for like 45 bucks with temp ranges to turn on at 200, off at ~170 , and also one that is on at 180 off at ~160. check around i think i saw some at the summit website. painless makes some and so does hypertech.

check out this article from thirgen.org: it tells about the factory settings and lists some aftermarket systems, and also the author made his own system in which the settings could be set back to factory settings with the flip of a switch. http://www.thirdgen.org/newdesign/tech/cool.shtml

Could be Fan Switch, Fan Relay or Fan motor itself. My 91 only has a single fan so not sure if there are 2 fan switches in your car or not. When mine went out it was the wire connecting to the fan switch on passenger side on the 6th cyl. You can clearly see the fan switch from underneath the car. should have a blue plastic piece on it.

Another option is to wire a fan switch directly to the fan relay and plug the new fan switch into the thermostat housing right up top. Otherwise you can find the correct wire in the fan relay, and wire your fans direct so they are on at all times.

go to pep boys and get a hayden temperature control relay and put that in yur car...it lets you control what temperature you want your engine to turn on at and its about 30 bucks.. put one on my 91rs and it works great.