95 Caprice Gremlins... Fans stay on constantly.

[thomasakehoe]

Hey everyone, I know diagnosing electrical issues is tough sometimes. I just need someone to aim me toward the right area to start checking. Background- 95 Caprice SW, 145K Miles. A few days ago I notice that the AC wasn't blowing cold anymore and the temp was creeping higher than it had before. I checked under the hood and only one fan was running with the AC set to on. And without the AC on no fans turned. Well I figured a fuse or maybe relay checked the fuses and the relays the primary relay seemed hot so until I could get to the parts store 25 miles, I swapped the relays and the one fan tuned on and off with the temperature gauge I replaced the other secondary relay and then all seemed well. Fans kept engine cool and AC worked awesome. A day or two later I put in a new air filter and after that the SES light was on and the fans blow constantly as soon as the engine is running. I looked over the engine bay for something that I might have broke or dislodged as far as wiring or sensor but didn't see anything that really jumped out. Any idea where or what I should check first. I'm going to be getting a EZ Scan next week but just spent all my cash on a twin turbo setup. I just don't want to start replacing sensor blindly etc... Car seems to run fine and has the same ammount of power. So I'm lost at the moment. Any advice appreciated.

[DJ_Kovacs]

when your MIL light is on, indicating a malfunction of some sort, the computer commands the fans on, and will stay on, and the car runs in limp mode.
peek around to see if you had bumped a sensor. If nothing is out of the ordinary, then you will have to get it scanned to pinpoint your problem, once the light is off, your fans will return to normal:thumbsup:

[thomasakehoe]

Yah thanks I read about the ECM turning the fans on to protect itself. Just was wondering if there was anything close to the air box other than the MAF that I might have messed up. Literally all I did was unbolt the two wing nuts lift up the lid and replaced the filer and then as soon as started the car the SES was on and later that day I noticed the fans were always on. Thinking about driving down to Advance Auto Parts and seeing if they can scan OBD1 cars.

[BrdwAtti2d]

This might seem too obvious but maybe the relay they gave you is either the wrong relay or defective?

[DJ_Kovacs]

if the relay is wrong or defective on the fans, then they wouldnt come on at all, and I dont beleive that would set a MIL


the IAT sensor is also on the intake elbow, you might check that

[thomasakehoe]

No the primary relay had gone bad previously, where the only way I could get any cooling was to run the AC and that only made the secondary fan run. I replaced the defective relay and all was well (no check engine light and fans worked properly) that is until after I changed the air filter and now the SES light is on all the time and the fans run whenever the car is running regardless of temp. Cooling system is full, no leaks. I'm thinking something near the air filter box must have gotten messed up but new to the Caprice and the Haynes repair manual is really only good for basic information. Just wondering if there is a sensor or part near the air box that could cause this malfunction. I also cleared the codes by disconnecting the battery for like 15 minutes and as soon as the car was started within 10 seconds the SES light was back on and the fans were running continuously again.

[BrdwAtti2d]

if the relay is wrong or defective on the fans, then they wouldnt come on at all, and I dont beleive that would set a MIL


the IAT sensor is also on the intake elbow, you might check that

Why would you think it impossible for a relay to be stuck closed? NOTO, never overlook the obvious.

[thomasakehoe]

Just asking but wouldn't that make the fans run even when the engine was off, I only ask because of the warning under the hood that says fans may come on at any time even when engine isn't running, as soon as I shut it off the fans stop but as soon as the engine starts to run they're on. Also the relays were in for a couple of days before I changed out the air filter and no problems. Then after the air filter was changed is when the issue with the SES light and fans running all the time started.

[BrdwAtti2d]

Yea, if the relay was stuck closed it's doubtfull the fan would shut off with the key. But that would depend on which fan had the stuck relay. I was just pointing out that it isn't impossible for a relay to get stuck closed and keep the fan running continuously. Get the SES code, that will take the guesswork out of the problem.

[thomasakehoe]

Hey sorry I wasn't trying to sound snotty or anything just trying to understand the cars control system. Today I went out switched the relays just swapped positions,car runs the same SES and fans run as soon as started, took the intake system off down to the ECM cover and cleaned everything and checked the MAF connector looked clean for its age, checked the connection to the IAT cleaned it and reconnected, no change, I don't have the cash today for a code scanner and my friendly auto part giant doesn't scan OBD1 cars. SO tomorrow I'm going to throw 15 bucks at the car in the form of a new coolant temp sensor for the ECM and if that doesn't fix it I will just have to monitor the car closely until next week when I can afford the EZ Scan 6000.

[IMPALADAKID]

Hey sorry I wasn't trying to sound snotty or anything just trying to understand the cars control system. Today I went out switched the relays just swapped positions,car runs the same SES and fans run as soon as started, took the intake system off down to the ECM cover and cleaned everything and checked the MAF connector looked clean for its age, checked the connection to the IAT cleaned it and reconnected, no change, I don't have the cash today for a code scanner and my friendly auto part giant doesn't scan OBD1 cars. SO tomorrow I'm going to throw 15 bucks at the car in the form of a new coolant temp sensor for the ECM and if that doesn't fix it I will just have to monitor the car closely until next week when I can afford the EZ Scan 6000.
I see this is kinda old, but I did not see mention of what normally creates these symptoms. There is a temp sensor in the front of the water pump. If it is disconnected or the wires are loose or it has failed. The fans and cel light will come on, because the pcm thinks the engine has overheated and or goes into default because it can not get a reading from that sensor.