69 Fleetwood "Engine Temp" Light Stays On

[RC Bizz]

The engine temp light in my 69 Fleetwood came on and stayed on a couple years ago, and I'm finally getting around to looking at it. The light stays on even when the car isn't running, so I need to disconnect the battery or it will drain while the car is off.

Wondering if anyone has any recommendations for where to start looking. I've seen a few forums posts through Google searching that mention a bad sensor, bad wiring, or bad fuses, but the posts were a number of years old and I never saw if the issue was fixed in any of them. Any guidance would be appreciated.

[Eric DeVirgilis CLC# 8621]

Need to replace the engine temp sensor (switch).

[RC Bizz]

Would that be the sensor on the driver side rear engine block that I am seeing people discuss?

["Cadillac Kid" Greg Surfas 15364]

Ryan
Good possibility of a grounded wire. Eather at the sensor or in the harness.
Greg Surfas

[76eldo]

Can it be a key switch issue? Does your key-in buzzer work when the drivers door is opened ?  Temp light also comes on with key in and drivers door open.

[cadillacmike68]

It could be a stuck key switch.

[Jeff Rosansky CLC #28373]

Squirt some sort of lube in the ignition switch and then put the key in/out several times to see if that cures the problem. The switch probably thinks the key is in it.
Jeff

[Glen]

Attached is the circuit diagram. 

[bcroe]

According to the drawing Glen provided, the warning buzzer will sound
any time the ENGINE TEMP TELL TALE light is on.  The key switch will
not do anything with the door closed, probably not the issue. 

Certainly I would start by unplugging engine sensors to see if one
will turn the light off.  Given that the symptoms don't match up
(light and buzzer), I am wondering if there is another light and
sensor than those shown in this drawing.  Bruce Roe

[Scot Minesinger]

There are two warning light to high temp on the 69/70 Caddy, one is hot block, the other measures coolant.  The light illuminates when ground is made by the sensors.  The hot block one I think is in back, the coolant one is under compressor with green wire.  Both are one spade connectors.  With engine off and battery disconnected pull each spade connector off and measure with ohm meter if the sensor spade connector is shorted to ground, if so that is the problem, ground should only be made if it is too hot.  If both sensors are OK, then look at ignition issue with key buzzer.

[Eric DeVirgilis CLC# 8621]

Only the "stop engine temperature" lamp can remain illuminated with the ignition off; coolant temp, to my knowledge, cannot.

[RC Bizz]

Thanks for all the replies. To answer the earlier question, the key-in buzzer does work, but only when the key is put in the ignition, as I would think it should.

Could anyone describe a rough location of where the engine temp sensor is located? I have heard driver side near the back of the block but haven't seen any diagrams or anything to get an idea of where I'm looking.

[klinebau]

Back left side (drivers side) of the engine, by cylinder #8.  Behind the rocker arm cover.  There may be a single green line running to it.

[Eric DeVirgilis CLC# 8621]

Thanks for all the replies. To answer the earlier question, the key-in buzzer does work, but only when the key is put in the ignition, as I would think it should.

As far as I'm aware, the buzzer and Temperature lamp always operate together. Maybe it's different in 1969...