I have a Service AC light on in my 91 Deville. It goes on and off, usually everytime you adjust the climate control it comes on, and then goes back off after a minute or so. It is also stuck in economy mode. WTF? Codes are F40, E52, F46, then it counts up 47, 48, 49, 51, then it says .f.f, F51, .7.0 I have only had this car for a month, so i don't know much about cadillacs, but i'm eager and willing to learn.

 

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What does that mean??

 

I have been having problems posting to this thread... it will probably screw this one up too. I made a thread int he website technical section of the forum. I wouldnt let me PM or email you either. i always got the forbidden message

 

trying again...

I looked up this info on alldata using my 1990 Cadillac deville which should be the same for you (I think, if not someone please correct)


F40 - air mix door problem

F46, 47, and/or 48 - refrigerant system problem

F49 - "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 "insufficient cooling" or "engine overheating" may be associated with this code."

F51 - "Code F51 indicates that the PROM (Programmable Read Only Memory) is not being read properly by the BCM. While the PROM error condition is present a "-151" will be displayed on the ECC and diagnostics cannot be entered. If the problem becomes intermittent, code F51 will be displayed during the first pass of BCM codes. A code E47 may also be stored as an intermittent after the problem is corrected since data is not sent to the ECM while a PROM error condition exists."

E52 - "This diagnostic test monitors the PCM/ECM long term memory for loss of data. If the battery power or ground are disconnected the code will set. Code E52 indicates that the "long term" memory in the PCM/ECM has been reset. This will be the case whenever power is removed from the PCM/ECM (i.e., disconnecting battery cables, disconnecting PCM/ECM connector, etc.)."

 

YES I figured it out.. apparently the forum doesn't like the equals sign. I was using that instead of the dash after the error codes.

sorry to make a mess of your thread

 

I'm not sure how much help I'm going to be.. I have never had theses problems. I will give it a whirl though.

First, did all of the codes come up a once (like in a same time period)? or did they show up one by one (like over a few weeks/months)? If so, which one came first?

Don't worry about E52 unless it shows up randomly. Other wise it will show up anytime you get a dead battery or you have unhooked the battery.

Then, if it were me, I would focus on why it is throwing F49. One of the possible reasons listed in my previous post would be an over heating engine. After driving it, park it leave the engine running and pop the hood. Make sure all fans are running. Being winter its possible the engine could be only running 1 fan (or no fans if you live way up north and its like negative something). Make sure you have enough antifreeze in the overflow/catch bottle also. You can even take the rad. cap off and make sure its full to the top.

the other possibility with F49 is the high side temperature. Since with a refrigerant the temp directly correlates with pressure that would mean you would have some super high pressure on the high side. If fans are operating properly and the radiator/condenser is fairly clean I would think there is not a airflow problem causing high side temp/pressure problems. Which leads to two other possibilities. First, the sensor is faulty and gives a super high temp reading for some reason and/or a short or open curcuit (can remember which give the high temp reading) in the wiring to the sensor. The other which I would say would have the least chance of being the problem would be a restriction in the AC system (like crud plugging up the orifice tube).

Now you said the service ac light comes and goes... would it come on when waiting in traffic or in a drive thru or somehting like that? If so that would suggest an fan problem.

I'm not to sure what to make of F51. I would hope that is a fluke of some kind... lol.

F40 I think I might have seen the air mix door motor when I had the glove box out, but Im not sure...

The only thing that worries me is if something electrical/computer is going bonkers on ya, and causing a bunch of the codes.

 

The check AC light only comes on when you start the car, or try to turn the system on. It is stuck in Econ mode. The only way you can get the blower to come on is to hit auto, but it will immediately go to econ. I havn't seen the fans come on. I will check. It never gets any kind of overheat light. When I first got the car like 2 months ago from a dealership, the AC blew ice cold. Maybe they just charged the **** out of it to sell it, and it has a leak somewhere.