Buick City Posted April 11, 2021 Share Posted April 11, 2021 My "90" overheated the other day ,the fans were not running! I wired them direct with a fuse ,to make it home,but would like to know where the sensor is that controls the fans to come on ! I couldn"t find anything in the FSM . THANKS Link to comment Share on other sites More sharing options...
Barney Eaton Posted April 11, 2021 Share Posted April 11, 2021 (edited) Below is the schematic for 1990 fans. The ECM get input from the temp sensor and controls the fans. You might have a bad relay. Edited April 11, 2021 by Barney Eaton (see edit history) 1 Link to comment Share on other sites More sharing options...
Buick City Posted April 11, 2021 Author Share Posted April 11, 2021 Thank you Barney ! Link to comment Share on other sites More sharing options...
Karlw144 Posted April 12, 2021 Share Posted April 12, 2021 There’s also 3 underhood relays to turn the fans on. They are in the relay center on the drivers side fender. Both fans should come on low when ac is selected. Then they should go to hi as conditions dictate. I can’t remember for sure, but I think there is one relay that turns both fans on low (when the ac is turned on) and then there are two more relays that will each turn one of the fans to hi. I replaced all 3 on my 90 and they work as described. Sometimes just unplugging and plugging together a couple of times will clean the contacts enough that they work ok. How this helps. Link to comment Share on other sites More sharing options...
padgett Posted April 12, 2021 Share Posted April 12, 2021 88 had to, 89 up had three, Allante had a module. Link to comment Share on other sites More sharing options...
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