ianhardgrove@hotmail.com Posted October 21, 2018 Report Share Posted October 21, 2018 I have a 1991 Allante and wanted some advice. My two electric fans are not working and I have changed out the relays, fuses and everything seems normal, except they still do not switch on. Has anyone experienced this issue and resolved it? Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted October 21, 2018 Report Share Posted October 21, 2018 To diagnose, consider the fans must be commanded on, the fans must get power, and the fans must operate when they get power. Checks: Are you getting power to the fans? If the fans get power, do they operate? If the fans operate under power, are they being commanded to operate in response to the appropriate temps? Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
ianhardgrove@hotmail.com Posted October 21, 2018 Author Report Share Posted October 21, 2018 Thanks Bruce for your prompt response. 1. The fans are not getting power through the normal startup system (they should automatically be engaged once the engine starts). I have traced power to the relays that operate them and they are getting the full 12V. I have replaced all the relays that switch power to them and they should be working accordingly. 2. I have tried applying power directly to the fans from the battery via patch cable and they are operating. I have replaced all the fuses I can find in these circuits. 3. The thing that alerted me to this issue is that the car overheated on a short local drive. I can't find any reference to a thermostat switch in the circuit that commands the fans to operate...I thought this might be a potential failure point? Appreciate any insights on this frustrating issue as it is a showstopper to using the vehicle. Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 21, 2018 Report Share Posted October 21, 2018 This is a 91, the OBD1 system will set trouble codes. Is the check engine light on? Do you know how to extract the DTC codes? What engine is this?, 4.5 or 4.9? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted October 21, 2018 Report Share Posted October 21, 2018 Did you also see this thread at justanswer? https://www.justanswer.com/cadillac/3cwez-allante-fans-overheat-a-new-temp-sensor-intake-manifold.html There is a fan control module which I suppose takes input from radiator temperature and commands the fans. may be pn GM 1641400 according to this post on ebay. I do see one reference to a reader dis-assembling the module and replacing components within it successfully, but just as likely to be a poor connection or broken wire that can be fixed so will need investigation. Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
ianhardgrove@hotmail.com Posted October 21, 2018 Author Report Share Posted October 21, 2018 It is a 4.5l engine and the engine light is not on. I wasn't aware there was an obd plug on the 1991, so will check with the links you supplied to see if I get feedback. I will also take a look at the justanswer link as that seems like a possible failure point. Many thanks!! Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 22, 2018 Report Share Posted October 22, 2018 Here is a 91 Allante code list and directions as to how to retrieve them. I dont see anything regarding the cooling fans.. I have a 91 Seville 4.9 Factory Service Manual, I'll look it over maybe it will be helpful. https://www.troublecodes.net/cadillac/91-92-allante-4-5l-vin-8/ Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
ianhardgrove@hotmail.com Posted October 22, 2018 Author Report Share Posted October 22, 2018 Awesome and thanks so much for the advice!! Link to comment Share on other sites More sharing options...
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