Electric fans will not operate properly

435

Asked by Jan 06, 2012 at 08:39 PM about the 1996 Buick Roadmaster

Question type: Maintenance & Repair

I have a 1996 Roadmast estate wagon with the duel electric fans (not a tow package car). The primary fan will turn on only when the gauge hits over 3/4 scale and the secondary fan does not turn on at all. The primary fan is the only one that will turn on when the A/c is on as well. I have checked both fan curcuits and both fans work and when the relays are triped they both will turn on. The temp sending unit has been replaced and relays have been checked as well. Could anyone tell where else to look? I have traced everything back to the computer and the only thing i can think of is the computer is not giving the signal to turn on the fans. Help! car does not over heat and overall runs fine but in summer will run hot at idle because fan will not turn on until late and will only stay on for a minute (or less) and shut back off.   

3 Answers

fan switch itself is bad,is under fans electeral hook up,this is where the fans hook under bottom of fan shroud.

7 out of 7 people think this is helpful.
435

Papa, Thanks for the quick reply. but there is no swtich located under the fan shroud of this modle. The fan relays are located in a fuse box located on the top of the passenger side fender well near the fire wall. I have checked both relay according to the service manuals instructions. plus I also manualy tripped both relays with a 12V source to check the fan curcuits and both fans worked fine. The problem seems to be that the signal that is needed to turn "ON" the relays themseves is not happening. Again I have checked the primary curcuit all the way back to the computer itself and everything is fine. I even replaced the temp sending unit just to rule it out. would you have any other suggestions?

3 out of 3 people think this is helpful.
435

The problem was solved. After performing a overheat test (installed carboard in "DIRECTLY" in front of the radiator) then mounted a mechanical temp gauge. Took the car for a spirited drive to heat it up fast and then brought it home and watched the temp gauge and the fan cyle action. the primary fan would turn on at 210 F then the secondary would turn on at 230 F. With the carboard in front of the radiator and the fans running full the gauge sat at 230 and the engine never even sputtered,knocked or choked once. once the carboard was removed the engine cooled down very quickly. once the gauge hit 210 F the secondary shut off then at 190 the primary shut down. the primary would cyle back on at 210. Knowing that with nothing blocking the radiator the engine would not reach 230 and for that reason is why I never saw the secondary cycle. So for you guys with roadmasters that DO NOT have a trailer tow package that is the deal on the fan cycling.

8 out of 8 people think this is helpful.

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