Radiator fan not working.

The fuse & relay would be the first place to check. Swap the relay with a similar rated relay to confirm it's bad or good. If it's good check for voltage at the fan itself, or by jumpering the fan by applying 12V directly to it. If it's no go, it's the fan motor. If it does work then you have to determine why it's not getting voltage during normal operation. (bad fan control module, ECU, wiring harness...)

Could the themostat be causing this issue as well. Clogged up not ooening or closing? Im trying to narrow down. I'm currently driving it now It feels like its losing power. Hard to accelerate. Not overheating yet but after 30-40+ mins it will.

The fan should come on immediately when you switch on the AC, if they don't then there is a problem. Thermostat and engine coolant sensors would not factor in for non-operational fans with AC on, rather something in the fan control circuit.

Ok. Thatll have to been done later. I just uninstalled/installed the themostat. Check engine light went out. Temp needle still wants to slide to overheating then settles back in the middle. Plus fans still not working. Is it safe to drive with no fans working.

Did you ever find out the cause of this?

I am having the same issue as well except we replaced the fan and it still isn’t working and when we are stopped the ac doesn’t want to blow cold anymore and the carts starts to get a rough idle

I wish you guys would have finished this thread or posted whether you ultimately found a solution. I have been having the same issue as Grahamcracker and Kingbncr with neither cooling fan coming on my 2000 Deville, even with AC on high. 2 different mechanics had previously been working on an overheating issue and replaced the radiator, water pump, thermostat, hoses, and coolant cap (so now I'm wondering if one of the mechanics bumped or screwed something up or whether radiator fluid shorted something else out as a consequence a while ago). I know the fan used to work prior to these replacements, as I noticed the fans working when the vehicle 1st overheated and I left the fans on to cool the engine - the vehicle was immediately towed to the dealer (who said it would cost gobs of $$$ and not worth it for an old car). So it was towed to a local mechanics, who couldn't fix the problem. So it was eventually moved to my "trusted" mechanic. After being "repaired", the vehicle overheated slightly on the way home and I was told the air may not have been fully purged out of the coolant line, so to continue ti fill and purge. My wife had enough and we subsequently bought a replacement vehicle and put the Deville on ice. Now I'm trying to revive the beast and have fixed almost every other issue, including new issues from sitting, including purging the air out of the coolant system, which is when I noticed that neither cooling fan now runs. So I checked fuses and they were good. I tried to use a multi-meter to test out the outlet holes for the relays to check for power. However, the outlet holes were too narrow for my leads. Then I direct wired the fans and got driver's side to come on. I was unable to get the passenger's side fan to come on, being direct wired, but I couldn't really reach very well so doubt I had leads in correct spot. So I was thinking relays and swapped out the 3 fan relays and still nothing. I'm getting the sense that it may be a wiring issue somewhere, which is sort of above my pay grade. I also haven't been able to find in my research which of the fans comes on for: (1) engine start up, (2) for AC turned on, and (3) when engine temp reaches a certain level. Thoughts? or anyone actually determine their own fix?

The lack of responses could make you doubt the usefulness of this site.

Follow. the purge line.It leads to the trans side onto the bleeder bolt.Take the bolt out,clean it out.Thats how the northstar bleeds its self.

Also the 2000 devilles have a fan temp control that screws into the radiator.If it's bad the fans won't come on.

Take the fan relay cover off the relay, turn the ignition on,then close the relay with your finger.The cooling fan should come on.If it does,then it's the temp. Switch in the radiator.

I had the s as me issue for a wh I'll le on my beautiful 98 Seville sts after changing everything purging GB the air out of the lines and replaced everything well it was still overheating changed th he relays still well then I remembered the northstar motors had bad grounding issues so instead of hunting down all those grounds I bought an aftermarket cooling fan relay harness with temperature sensor for about $30 so now I can set it manually to what temperature I want the fans to kick on well I'm here to tell you that was four months ago and i drive this car dailyhasnt yet to overheat on me these are high maintenance cars and you just gotta take care of them more than a regular ol car ..#CadDiLLaCfanatic

Cadillacs are money pits , buy a Toyota Avalon and thank me later

Thanks Charles. I did take out the bleeder bolt (what other threads seem to call the hollow bolt). I also repeatedly cleaned out the 2 small lines that run across the top/front of the engine. Cleaning those 3 pieces were key to purging the air and bleeding the system. I also found the heater core was blocked up tight, probably from a prior owner adding a radiator stop leak. Having a couple extra hands to help squeeze air out of the upper and lower radiator hoses also helped. Also thanks Charles for the info on the temperature control in the radiator. You are the 1st person to mention it and point in that direction. There are many people like Guru7YZN1 who seem to just hate the Caddys. I like toyotas too and had 2 but the Caddy Deville is a wonderful vehicle (albiet the Northstar engine is sometimes frustrating to learn but is also interesting to work on). Definately pros and cons to Northstar engine design and I have met several Caddy mechanics that absolutely love them or hate them. However, its a machine and shouldnt be this big mystery to keep running, you just need some wisdom, determination, additional time for preventative maintenance and great mechanic(s) to assist with weird issues (i.e. things that arent common with other cars). That is why I appreciate all the help and responses here. Thank you all for helping and caring.

@ Wxpilot. Keep us up to date on this issue.

The computer sends signal to a fan control module. Delco 15-80803 . This module controls fan speed. If temp gauge works, and fan comes on with AC on high, it it probably this part. same for so many other electric fan vehicles. especially old jeeps.