Cadillac Repair: cooling temp light, fan module, climate control

Question
bill, 87 sedan deville,the cooling temp light comes on and off when i turn on the climate control until i get to 42 to44 mph then it goes off and will stay off until speed declines to that range i have changed the module several times and also cleaned the ground wire on the engine block, also changed 1 cooling fan motor , both fans operate properly is  there a repair for this problem. thanks dennis

Answer
Hi Dennis, Sorry it took me so long to return the email. The F41 is kind of a complicated code to test for and useing the Caddy shop manual would be a big help. Basically what the code means is that the F41 will set if one or both fans is inop, if one or both are slow to operate or if they use too many amps to run. Back in '87 they had fan module troubles but that shouldn't be the case anymore. I would suspect that if you replaced the LH fan motor maybe the RH motor is the cause of the light but without testing to see how many amps it takes when turning you won't know for sure. Heres what I want you to do. With the key on but engine not running push and hold the off and warmer buttons on the climate control panel for 5 seconds or until the dash goes into diagnostics. Then when the fuel data panel displays the codes and shows 7.0 push the econ button and the display will change to F.8.5   Push and hold the Hi fan button for 30 seconds and both cooling fans should turn on. Make sure they do. Then push the low fan button and both fans should turn off. Do they? Also when the fans are commanded on the "AUTO FAN" will light on the climate control panel and when the fans are commanded off the "AUTO FAN" will be off. Let me know what happens. If this doesn't make any sense to you then you will need to find someone that knows how to diagnos this code. Bill