fivepointohman Posted June 3, 2008 Report Share Posted June 3, 2008 When the AC is on, do both cooling fans come on? Only one of mine does... Just curious.... Link to comment Share on other sites More sharing options...
Cadillac Jim Posted June 3, 2008 Report Share Posted June 3, 2008 When the A/C is on, the fans are on in low speed. Low speed hooks the fans in series, so they both should run. If one is running and the other isn't, then the stopped one is jammed or something is blocking the blades from turning. With the engine off and cold, I would turn the blades by hand and clear any obstruction I found. If either or both are hard to turn after clearing away any obstructions, I would replace both of them. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
fivepointohman Posted June 4, 2008 Author Report Share Posted June 4, 2008 When the A/C is on, the fans are on in low speed. Low speed hooks the fans in series, so they both should run. If one is running and the other isn't, then the stopped one is jammed or something is blocking the blades from turning. With the engine off and cold, I would turn the blades by hand and clear any obstruction I found. If either or both are hard to turn after clearing away any obstructions, I would replace both of them. Well both fans spin freely... the passanger side spins, drivers side doesn't. I'll check voltage to the fan tommarow... Link to comment Share on other sites More sharing options...
JasonA Posted June 4, 2008 Report Share Posted June 4, 2008 I may be mistaken, but I don't think the fans ever spin at different speeds, or one is on and one is off. If one is spinning, the other should be as well. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 4, 2008 Report Share Posted June 4, 2008 I had a dead fan on my 91, they are easy to replace, just replace the bad fan... you will run cooler 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...
stsjoe Posted June 4, 2008 Report Share Posted June 4, 2008 I'll double check but I think one always runs with the A/C on (Drivers side I think), the other is coolant temp activated but they both go to high when it get hot enough Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 4, 2008 Report Share Posted June 4, 2008 Block the radiator to get the temp up to 228 and they run on HIGH and see if they both run. If what Jim saw in his manual is right, if they are in series they both should run when the AC is on. Easy to determine if motor is bad, disconnect the connector and check the motor with an ohm meter 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...
stsjoe Posted June 4, 2008 Report Share Posted June 4, 2008 Follow up, just checked a guy I work withs 95STS, stone cold no fans, stone cold AC on both fans. Jim made the call Link to comment Share on other sites More sharing options...
fivepointohman Posted June 4, 2008 Author Report Share Posted June 4, 2008 Follow up, just checked a guy I work withs 95STS, stone cold no fans, stone cold AC on both fans. Jim made the call Well guys, AC on 1 fan the larger one on the passanger side.. So I ripped out both the fans.. The drivers saide fan work with 12V dc well.. Turned AC on, no voltage from the wiring harness... So I had my one fan wired to a toggle switch under the dash anyways. So I rewired the both to my toggle, Problem solved and now I have safe insurence and control over when the fans should kick on.. So with the 90 degree weather that is expected in NY this weekend, My fans will be on, whenever I want them to be free and clear of any overheating issues... Problem solved... Link to comment Share on other sites More sharing options...
jackc Posted June 5, 2008 Report Share Posted June 5, 2008 OK - I'll bite. Your fans are on a toggle switch???? Link to comment Share on other sites More sharing options...
fivepointohman Posted June 5, 2008 Author Report Share Posted June 5, 2008 OK - I'll bite. Your fans are on a toggle switch???? Yes, I made my own circuit, both fans wired directly to the positive side of the battery and the toggle ( 30A ) connect to the ground.. Drilled a small hole in the firewall. Ran wires under the dash and mounted a switch under the dash non visible where I can use my foot to switch it on and off... No more worries! Link to comment Share on other sites More sharing options...
jerrymac Posted June 5, 2008 Report Share Posted June 5, 2008 Hmmm , foot operated cooling fans, now why didn't GM think of that. Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 5, 2008 Report Share Posted June 5, 2008 This was probably just a bad relay in the trio-of relays under the radiator 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...
fivepointohman Posted June 5, 2008 Author Report Share Posted June 5, 2008 This was probably just a bad relay in the trio-of relays under the radiator Probably, But It not worth finding out at the expense of a blown headgasket... It's a clean job, No visible wires or modifications anywhere... just a controlable way to cool the car on que. Link to comment Share on other sites More sharing options...
JasonA Posted June 5, 2008 Report Share Posted June 5, 2008 You may consider powering the fans through a relay instead of directly to the battery. Just don't forget to turn the fans on/off. My roommate in college had an older F-body with this type setup. I guess the original cooling fan circuit crapped out, or a previous owner converted to electric, or something. But one time he forgot to turn the fans on, and the engine was sitting at about 240*F cruising around campus. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 5, 2008 Report Share Posted June 5, 2008 This means that your fans are running full speed while they are on and that YOU must monitor temps to turn them on and off, assuming you ever turn them off. It is not likely that ONE fan out would have caused overheating so badly that you would have endangered a headgasket. What you should do is identify what relay is related to the inoperative fan, swap in a good relay and test for voltage then put it all back the way it was. We would have been glad to post schematics of the relays and diagnostic trees to help you FIX this. As it stands you will NOW have a problem if you ever want to sell this car with this Rube Goldberg setup. If you look at my profile you will see a quote from my Dad who was a B29 mechanic, "Do it right, or Don't do it at all". This is not criticism so please don't take it that way, I actually hard wired the fans in my 91 because when they did my tranny they pinched a wire between the engine and tranny and it blew a fusible link (that car was in the junk yard within 6 months) 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...
jackc Posted June 5, 2008 Report Share Posted June 5, 2008 The big advantage of the OEM set-up is that it'll maximize temperature STABILITY, to the extent that it can be maintained by the fans. We'd be working hard to get to the same end doing it manually. And stability has been cited as a key to longevity with an aluminum engine. Link to comment Share on other sites More sharing options...
JasonA Posted June 5, 2008 Report Share Posted June 5, 2008 With the fans running constantly on, the engine temperatures will still be stable. Engine temperature is controlled by the thermostat, until the coolant in the radiator is hotter than the thermostat's set temperature (like, if the fans aren't running), at which point the thermostat just holds at wide open for maximum flow. Then and only then do the fans influence the temperature...but only until the incoming coolant is colder than the thermostat's set temperature, then the thermostat will begin to close again. In that sense, the engine sees MORE thermal cycling due to the nature of the electric fans -- they don't come on until 230*F (unless the A/C is on). So you actually see a LOT of engine temperature cycling with the OE setup. Running the fans constantly on will ensure that the coolant temperature always runs as cold as possible. However, the thermostat will always cycle a little bit to keep the engine running at the prescribed temperature (near 200*F, give or take). The temperatures will be MORE stable with the fans always on, because the temperature will never rise above the thermostat's setting. The "draw"back, so to speak, will be the electrical draw of those fans always on (plus the noise). I'd still re-wire the system to go through a relay. But in terms of engine safety, as long as the fans are always running, that engine temperature should always stay a rock-steady 200*F or thereabouts. It'll be a waste of energy to have the fans always running, but that'd be the price to pay for absolutely rock-solid temperatures. My brother's C5 Corvette has a supercharger and a chip that locks the fans on high all the time. It's loud, and probably draining on the alternator, but the engine temperature won't come off 180*F to save its life. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
jackc Posted June 5, 2008 Report Share Posted June 5, 2008 Interesting. I stand corrected. Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 5, 2008 Report Share Posted June 5, 2008 Good point Jason, very good understanding of the cooling system..I was with Jack till I read your post 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...
fivepointohman Posted June 5, 2008 Author Report Share Posted June 5, 2008 Good point Jason, very good understanding of the cooling system.. yes, I agree, the temp stays rock solid at all driving speeds etc... It is overkill but its a safe way to drive and yes the leaving the fans on is an issue, as I once already killed the battery, however, I believe a Key on relay inline is best so I will be looking for a such solution. Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 5, 2008 Report Share Posted June 5, 2008 Buy one relay and swap it into each position on the trio of relays and I am sure you will find your problem. Ill look in the manual later, I am sure you had a simple problem. 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...
BodybyFisher Posted June 6, 2008 Report Share Posted June 6, 2008 Ok I just looked at the cooling fan schematic, the PCM grounds circuit 335 (dk green), that energizes both cooling fan motors. BUT. Power is supplied to the motors through the cooling fan 1 relay, contact circuits (your #1 relay is good as one fan runs). Relay 1 energizes circuits BLK (532), White (504) and Lt Blue (409), and COOLING FAN #2 RELAY contacts. The fans are connected in series circuit, thereby sharing the 12 volts equally causing them to run SLOW or LOW SPEED. As a result of this, I would check cooling fan relay #2. If the contacts are bad, the second fan or the RH fan energized through Lt Blue (409) won't run. Check the #2 relay, it will be the relay with WHITE, ORANGE, LT BLUE and DK BLUE wires going into it. My guess is that the LOW SPEED contacts are burned, if you tap it with a broom stick while the AC is on, I would not be surprised if the fan started. You could take the relay apart and inspect and clean the contacts or replace it.. Mike 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...
BodybyFisher Posted June 6, 2008 Report Share Posted June 6, 2008 Buy one relay and swap it into each position on the trio of relays and I am sure you will find your problem. Ill look in the manual later, I am sure you had a simple problem. I take this back....after looking at the relays, #1 and #2 are different 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...
fivepointohman Posted June 6, 2008 Author Report Share Posted June 6, 2008 Buy one relay and swap it into each position on the trio of relays and I am sure you will find your problem. Ill look in the manual later, I am sure you had a simple problem. I take this back....after looking at the relays, #1 and #2 are different Well I tell ya what, After a 98 degree day the fans needed to be on at all times! The car went to 1 line past the 12 oclock position and I was definetly freekin out. IDK.. i did go to a shop to have my coolant tested, It never turned yellow which meant to gases in the coolant... So that was good. But this car runs blazing hot in the summer months! Link to comment Share on other sites More sharing options...
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