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95 Eldo Ac/Heat and Overheating Problems


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My 95 Eldorado runs great, but lately I've had problems with it overheating, or at least coming close to overheating. One day I was sitting in traffic and on my dash was a message saying somethng like "Shut off Engine" or something like that, I can't remember the exact phrase. I immediately switched the dash display to engine temperature and it was nearing 250 degrees. Just then I started moving and slowly the temp began to drop but I made it to a car wash and decided to let it sit for a while and cool down.After about 15 minutes or so I got back in and the temp was around 230 and as I drove at a speed of about 55-60 MPH it began to come down. It went down as far as 200 at one point but stayed around 215. After that I noticed that as long as I was moving steadily the temperature stays somewhere around 210-220 degrees but if I sit idle for a certain amount of time it rises. Thankfully it's only gotten to the overheating zone only that one time. I am thinking the thermostat needs to be changed. Maybe fan? Any other suggestions or opinions?

Now, My A/C and heater seem to be dead. No air will come out. I can hear it come on when I turn it on, but it blows no air. Sometimes in the mornings when I first crank it up and let it idle to warm up air will blow out, but as soon as I put it in gear it will shut off. It still comes on but only by surprise. Most of the time it doesn't blow out any air. I'll be driving down the road and air will just come out but only for a couple seconds at best. Maybe blower motor? Bad connection somewhere? A/C recharge? I don't want to take it to a shop just yet because cash is pretty tight and I'd like to fix it myself if it is something I can fix myself. Anyone have anything to suggest?

Edited by barkboy6
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If the t-stat is the original, time to replace it along with a radiator cap. Either could cause the strange temps. When air is moving through the radiator, it seems to be removing the heat, so I'd be checking the fans.

What codes are shown?

The blower motor may be shot or have a bad electrical connection.

GM Reman 4.1 engine Dec '08

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This sounds like you have a relay or fuse out on the radiator fans. Also the bypass and the heater core may be blocked. I would look at the coolant, and consider having the system flushed, including the heater core and bypass hose.

Your symptoms don't sound at all like a head gasket, but on the remote chance that there may be head gasket leakage you might have the coolant checked for combustion products before you flush the system and don't have anything to test. That way you can eliminate that and forget it.

One simple way to check your fans is to start the car and make sure the A/C is turned on. This will run the radiator fans at low speed if everything is working properly. Check the hood and if they are not both running, then there is a problem with the radiator fans.

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-- 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.

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Ok thanks for the info. I turned on the car, turned the A/C on and checked the fans and saw that neither fan was turning. So I checked the fuses and found that the red 10 was blown. I pulled the 10 fuse from the left low beam just to run a quick check and still neither fan turned. Any other suggestions?

How can I check the blower motor? And how can I check codes?

Edited by barkboy6
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In my 1997 FSM, the schematic on page 6-176 shows that there are two fuses to check. There is a 50 Amp fuse in the RH MaxiFuse Block labeled COOL FANS. There is a 10 Amp fuse in the Engine Compartment Fuse/Relay Center labeled 10 Amp. It's beginning to look like the 50 Amp fuse might be bad because that is the one that passes power to the fans. The LH and RH Maxifuse Blocks are two columns of large automotive fuses in the engine compartment on the driver's side; the LH is the left one and the RH is the right one -- looking from the front of the car.

The three fan cooling relays are on the bottom of the fans. The big red wire to two of the three relays carries power form the 50 Amp fuse. You might be able to check there with a voltmeter or test light. It should show 12 Volts there, even with the engine off and the key out.

If the A/C is blowing cold air, the 10 Amp fuse is OK because it is also the fuse for the compressor clutch relay. You can also use a voltmeter or test light to see if there is 12 Volts on the orange wire to all three relays; if so this fuse is OK.

With the fans in Low Speed, Relay 1 is actuated and the fans are in series (6 volts across each). In High Speed, all three relays are actuated and there is 12 Volts across both fans.

CTS-V_LateralGs_6-2018_tiny.jpg
-- 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.

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I checked the 50 amp fuse first and saw that it is still good. That's when I checked the other fuses and found the bad 10 amp.

And since the fans do not come on at all, would that mean Relay 1 may be bad, since it's the first one to be used?

My A/C isnt blowing out any air. I can hear something "come on", I guess, when I turn it on but no air will come out. Even the heater, but at least the heater does warm up and blow out just a little air because I can feel it from the defrost vents and it'll work good enough to de-fog the windshield if needed but that's about it. That's why I'm thinking something is wrong with the blower motor because isn't that what blows the air out of the vents?

Edited by barkboy6
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