Help! dead battery

[jgaugie]

2005 XLR. Several times after engine shut down the engine cooling fan begins to run and if not noticed it will run until the battery is dead. Why and how can I correct the problem?

 

[rexster314]

2005 XLR. Several times after engine shut down the fan begins to run and if not noticed it will run until the battery is dead. Why and how can I correct the problem?

Take it to a local auto parts store and have them stress test it. More than likely it's done like a well done steak

 

[ccclarke]

I'll take a look in the books tonight for something sensor-related and add to this if I have anything useful to contribute as to why the fan is running for extended periods.

CC

 

[rexster314]

2005 XLR. Several times after engine shut down the fan begins to run and if not noticed it will run until the battery is dead. Why and how can I correct the problem?

Does it run immediately after shutdown, or about 45 minutes later? I have enabled the hvac fan to run after parking the car to alleviate and stop the urine smell you get sometimes from the a/c. Condensation can form and will get really funky if allowed to sit and marinate for a day or two. Now, since enabling the fan to run after shutdown, it evaporates the condensation formed. It will come on automatically after 45 minutes.

 

[ccclarke]

Thought not specifically mentioned, he may be referring to the electric engine cooling fan instead of the HVAC afterblow feature you've enabled.

CC

 

[rexster314]

He probably is, just throwing it out there. Previous owner could have had it done and OP doesn't know about that feature

 

[jgaugie]

Does it run immediately after shutdown, or about 45 minutes later? I have enabled the hvac fan to run after parking the car to alleviate and stop the urine smell you get sometimes from the a/c. Condensation can form and will get really funky if allowed to sit and marinate for a day or two. Now, since enabling the fan to run after shutdown, it evaporates the condensation formed. It will come on automatically after 45 minutes.

It is the engine cooling fan not the HVAC fan that turns on without warning. I have never waited to see how long it takes to turn itself on. It only has happened maybe ten times in the past several years and most of the time we have heard it when entering the garage later in the day and turn it off manually.

 

[jgaugie]

Thought not specifically mentioned, he may be referring to the electric engine cooling fan instead of the HVAC afterblow feature you've enabled.

CC

It IS the engine cooling fan that turns on. I have edited my thread to state that fact. Thanks for the thought.

 

[ccclarke]

The engine cooling fan is controlled by the ECM (Engine Control Module) through several sensor inputs. It will command the fan to run at variable speeds depending on what it perceives is the right amount of cooling required.

The fan will be commanded to the ON state when the following conditions are met (all temps/pressures are approx.):

1. The engine coolant reaches 204 F. The fan will switch to high speed when the coolant temp reaches 235F.
2. The A/C pressure reaches 87 PSI. The fan will switch to high speed above 360 PSI.
3. If the engine oil temp exceeds 302F, the fan switches to high speed.
4. If the transmission oil exceeds 270F, the fan switches to high speed.
5. When the engine is shut OFF, if the coolant temp is >235F, or the A/C pressure is >249PSI, the cooling fan turns on @ low speed. When the coolant temp drops to <230F and the A/C pressure drops to <241PSI the fan will shut off after two minutes of operation.

With a couple of beers and a Tech 2, this is a relatively easy problem to troubleshoot. You would note the parameters of the temps and pressures to determine which sensor is staying high after a few minutes during fan operation. The ECM could also be suspect. If you don't have access to a Tech 2, it wouldn't hurt to take it in and have a shop determine which part(s) is causing the fan to remain on.

My long-distance, psychic hotline, best guess, is a faulty sensor as the most likely culprit. Until you get this diagnosed and repaired, it might be easiest to park indoors with the driver's window lowered, the hood unlatched, and the battery disconnected.

CC

 

[jgaugie]

Thanks for that great info. I thought that perhaps it might be a sensor problem of some kind but was not sure if there was such a thing controlling the fan. I have a technician who can check it for me. He is a retired former Cadillac service mgr who really knows his stuff. He solved a problem I was experiencing relative to a CHECK ENGINE light that was giving me fits. After nearly $1000 and several trips to a Cadillac dealer I found him and he corrected the problem. He checked all the inputs and parameters that kept giving the O2 sensor false readings and finally found that all the intake manifold bolts were loose. The engine had apparently been taking in air where it obviously shouldn't have been. Something the dealer should have found the first time I took it in. So much for the "expert" advise one sometimes receives at the dealer.

 

[ccclarke]

A little additional info that might be of help . . .

The Service manual has a troubleshooting guide for this problem. After running a Tech 2 scan, it suggests replacing the Cooling Fan Speed Processor followed by the ECM.

CC