1987 Cadillac Deville Worning Light

If you press and hold off and warmer on your climate panel, what are the codes that display. The will display on the fuel data center, and will be prefixed by an E of an F. The ones we could be concerned about will be F codes, F41, F48 for example. Initially there could be a fault with the body control module, or the coolant fans control module. In this system, they work together.

7.0 indicates that all codes have displayed. After you press of and warmer, it will display codes. If it just goes to 7.0 then there is no codes. That system can do several things through the climate panel, you can read sensor data, execute overrides, and perform switch tests.

I wanted you to give me the codes and I will tell you what they mean. This is to find out if they have any relevance to your concern. You might be able to override and make the a/c compressor come on, but that is just for test purposes, and will olnly occur when in diagnostics. The reason the compressor may be shut down, is for protection. If there is a leak in the system, you would not see it, or smell it. If the compressor continued to run, it would eventually seize. The refrigerant also carries oil for lubrication. When you select auto on your climate panel, does it default to econ on it's own?

In theory, the vehicle is overheating. Does it seem to be overheating? If the cooling system has been drained, sometimes these motors can have some air trapped in the cooling system. When the red light is on, can you touch the upper radiator hose, is it hot? If it is not hot, there is no flow. This could be for a few reasons. The thermostat is not open(if there is air behind it, it may not open). There could be a restriction in the system, if you replaced the radiator I would not suspect that. The water pump could be faulty, have never seen it but it is a possibility. You could also have a blown head gasket. Is the coolant level full? Here is what code description for F49 states.

DESCRIPTION:

To protect the vehicle's cooling system from overheating, the BCM commands the compressor clutch to disengage if the coolant exceeds 126 °C (259 °F). Also, if the A/C high pressure refrigerant temperature exceeds 93 °C (200 °F), the clutch is turned "OFF" to prevent refrigerant "blow-out." Code F49 is stored by the BCM whenever the clutch is being disengaged due to one of the above conditions. Customer complaints of "insufficiant cooling" or "engine overheating" may be associated with this code. If a hard or intermittent code F49 has been stored, the coolant and refrigerant systems must be investigated for the cause of a high temperature condition. Possible causes would include blockage in coolant flow, blockage in refrigerant flow or insufficiant air flow over radiator/condenser.

Sorry, at first I was mislead, and what misled me was the word fan. If I remember right, this also has a cooling fan warning light, and there is different diagnostics associated with that. It sounds like you have an overheat condition for some reason.

One other thought, do you have heat coming from the heater?

If there is no heat, you could have two possibilities. Either there is an air pocket in the system, or the thermostat is not opening. No coolant around the thermostat can prevent it from opening. There is a hose that comes from the heater, it has an elbow and changes diameter where it connects to the thermostat housing. On the other end it connects to either a plastic tee, or the heater control valve. If you disconnect this hose at the small end, tilt it up, and pour coolant(or water) down it into the housing, you are filling the chamber behind the thermostat. Reconnect it and run it. That is essentially filling up the chamber behind the thermostat, and the warming may warm it. If you look at the geographics of it, it sits the highest in the system, above the radiator fill. That is where air can get trapped. When you get heat from the heater, that will indicate you have flow, and it should no longer overheat.

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