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Cadillac Repair/1998 Cadillac HVAC Blower motor


QUESTION: My 1998 Cadillac Eldorado ETC A/C Blower motor will not shut off, even when the car ignition is off and the car locked. It drained my battery over night. I unplugged it under the hood at the motor to stop it. Dan

ANSWER: Hello,

Another common flaw Cadillac had dating as far as 1982 that even though redesigned, still cost the owner headaches like their wonderful junk VATS that strands owners, but didn't stop theft, the fine Saginaw steering column that grossed us millions of dollars over the years being susceptible to theft, by a teenager with a screwdriver on the left side of the steering column in 30 seconds and their fine aluminum engine that if overheated self destructs. You would think for the money charged for these cars new that they would have fixed inherent problems that lasted decades, but it was just probably job security built into the car for the dealer. The dealers do not deserve the business to gouge the customer's eyeballs out.

Look I have owned over 20 Caddys and have worked on them since 1979, so obviously I love them, but GM saw the potential for continual business with the attitude "We have you don't." Unfortunately for all dealers taking advantage of victims, I was innovative to start my own business in the 80's taking the work they thought they were entitled to.

There are two different types of set ups here and I think yours is too new to have the non-servicible blower speed module located under the hood near the firewall. In this style, it is a bakelite piece with all sorts of wires going into it above the a/c penium, with one wire leading to the heater blower near the passenger side hood hinge. These were about $400 and and not available anymore. The fix was to make a two wire harness with an in line fuse and put one side to ignition power with a toggle and the other end to the blower motor.
Unfortunately, on yours, you probably have a bad BCM (Body Control Module-computer) that will need replaced, because just about everything for the electronics in the vehicle is tied into there.

Good luck.

---------- FOLLOW-UP ----------

QUESTION: Would that BCM also cause non recognition of the ignition key. On occasion the car acts like the key Does nothing. The "car is about to be stolen", or something to that effect.

How about a Variable rheostat or 3 way step-down switch on the white wire going to the HVAC blower. Will that eliminate the problem????

My Auto trunk open and gas cap door also quit(Together) with no fuse problems or trouble with other items on the same fuse. Is there a common connector and where is it. I can do the work myself. Dan


A BCM controls just about every function of the body electrical. Look, I am going to be honest and although I have a tremendous amount of information in mt head, I will admit when I certainly do not know. I hope you respect answers like this so you are no chasing down bull crap from someone.

The BCM could indirectly affect the engine's starting capabilities. I say this because at the very least, it can give you the three minute warning where the engine may not start message.

I believe this car has the VATS in it and it is antiquicated and problematic and can leave you stranded and the dealer will charge up to $700.00 for a new ignition lock and harness.

The way to determine if the vehicle has VATS is by the big ugly black resistor on the ignition key.

This was called VATS (Vehicle Anti-Theft System). The only problem is as you may know has a time/date for effectiveness. What if you had a computer from 1986? How good would that be?

The system was first introduced on the 1986 Corvette and it did reduce the theft rate by driving the vehicle for about two years. At that time the system also called pass key had 15 different valued resistors on the ignition key. By 1990, VATS was commonly bypassed for an aftermarket remote start system. The stand alone remote starts and alarms with remote start capability came with the 15 different valued resistors. The matching resistor for the ignition key would be placed in line under the dash, basically lying to the vats module that the correct resistance key was being used to start the engine. All these remote start alarms and stand alones came with the "VATS bypass"  pack of resistors, for no matter what type of vehicle it was going in. This meant that the installer had many extra bypass kits.
In 1992 pass key II was introduced. This took the amount of resistors for this system to 14 instead of 15, and there were some internal electronic changes.

The system was comprised of an ignition lock with a two wire harness. These two wires were very thin like old land line telephone wires. This harness went down through the steering column to a connector with the matching thin wires. It was very common for those wires to break inside the plastic insulation, so the break could not be seen. Using an ohmmeter, one could place the key in the ignition lock and attempt to take one lead from the ohmmeter and touch it to the resistor and the other lead placed on the wire on the column side of the connector. If there was no reading, there was a broken wire, but as one moved this harness around, the wire would go back together and one had no idea as to where the wire was broken.
One of these thin wires ran up the steering column to an electrical contact in the ignition lock. one other contact was for the wire running down the steering column. With the key inserted into the lock, the resistor met both contacts and completed the circuit.

For bypass, the resistance value was read from the key with an ohmmeter. The harness from the car was cut and a resistor of the correct value (within 10%) was installed, there by eliminating the steering column harness all together, and eliminating VATS issues and the thee minute warning.

I usually recommend sending the car to an alarm store and having them bypass the VATS for $60.00 or less. Its just easier that way.
The dealer will never do this, because they want to sell the owner of the car parts. Ignition locks that were never made by GM or neither were the keys. These parts were manufactured by a sub-contractor, who was Strattec of Milwaukee. The same originator that sold to locksmiths and locksmiths sold these ignition locks and keys for at least half the cost of a dealer.

That is what I know about VATS and their inherent problems as well as solutions.

As far as the trunk and the fuel door, yo might be correct about a disconnected common connector. If you are going to do your own work other car, the best priceless tool is a 1998 Cadillac Eldorado service manual. You should be able to find one on Craigs or Ebay. Working without this manual is working in the blind where any repair can be frustrating, yet most of the answers to the problems are in the manual.

You can attempt to see if there is a manual you can download for $30 at I don't know how far they go back and you will have to check.

On the HVAC. Blower speeds are controlled just like the VATS with resistors. I do not know if a rheostat will work or not, however, headlight switches get very hot and I really don't know if I would try that and I definitely would not try a three way switch because of fire potential. That is why I recomend an in line fuse even for a power switch. I have seen these switches fry or the wiring leading to the switch fry.
The reason I say run the toggle from ignition switched power is because the battery will never run down  again. Your ideas are good, but I just get a little nervous with these modifications, because of fire potential.

Good luck Dan.  

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Rob Painter


Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?


Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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