Rebuilding the Theft Alarm

A number of years ago I started to get random "Service Theft Alarm" messages on the SID. I replaced the batteries in the alarm and all was well. Last year the service theft alarm started to pop up again. The alarm also started to go off at random times when the car was locked. I searched the SAAB forums and learned that this was probably the 10 year old electrolytic capacitors had given up the ghost. The following post http://www.saabnet.com/tsn/bb/9-5/index.html?bID=208376 gave me the proper values for the capacitors.

330 uf, 25V
220 uf, 10V
10 uf, 16V

I ordered the capacitors fro Digikey. The Dikey part numbers are:
330 uf, 25V P/N P13123-ND (This C4 in the alarm circuit)
220 uf, 10V P/N P12920-ND (This is C2 in the alarm circuit)
10 uf, 50V P/N P10316-ND (This is C1 in the alarm circuit)

Little known fact; if you use Digikey's order form and mail in the check they ship for free. I mailed them a 65 cent check and got my parts in a week.

While I was in there I decided it was a good idea to change the batteries. They are somewhat expensive compared to the capacitors. I ordered part number CR17335SE from Battery Specialists . They were $23.90 for the pair, again with free shipping. I am on a roll. The batteries were expensive, but the batteries there were in there were several years old and I hate removing the inner fender.

The tools you need for the job are:
Lug wrench
Jack, & jack stands
T-25 Torx driver
8mm socket
10mm socket
#2 Phillips
Very small flat screwdriver (to pop the connector)
Soldering equipment.

Start by taking off the inner fender. To do this raise the car up and take the left front wheel off. Remove all the fasteners for the inner fender. Be careful with the two 10mm nuts on top and in the center of the inner fender. They can break easily. Once they fasteners are out carefully wrestle the inner fender out and set it aside. Look toward the from of the car and you will see:

Carefully remove the red connector from the alarm using the tiny screwdriver. The alarm comes off the car with two 10mm fasteners.

Here it is out on the bench ready for rebuilding.

Once you remove the 6 screws that hold the alarm together here is what you will see. You may have to pry the cover off if the two halves are sealed together. I have labeled the major components that you will be dealing with. The little red jumper at the bottom (J2) is used as a switch for servicing the circuit. In this picture is is shown in the "on" position.

Remove this jumper and turn itn 90, then slide it back on one of the posts as shown above. This disconnects the battery so you won't damage the circuit or cause sparks while working on the components. This also serves as a keeper for the jumper so you don't loose the jumper.

I made a quick sketch of the circuit before starting work. It is a good idea to do this so you have all your bearings when it comes time to put things back together. Note that the "+" side of all the components face the same way. This is typical of many circuits as it makes assembly and inspection easier in the factory.

At this point I have removed all of the offending components. Note the board was factory coated with a sealant to prevent corrosion. This is done by dipping the completed board into a pool of sealer just deep enough to coat the board and the very bottom of the components. This seals moisture out and glues the components to the board which makes them a bit more vibration resistant. This is very apparent on the batteries where you can see the orange-brown coloring from the original batteries that remains stuck to the coating.

How to remove the components? One way to remove the components is to heat the solder with an iron while prying the component. This can damage the board, and you will end up with a hole that is filled with solder. Plan "B" is to use a material called solder wick to remove the solder from the hole. Another alternative is a solder sucker, which is a professional tool that heats the solder as it vacuums it off the circuit.

In any case, you want to be gentle as possible to prevent damage.

Here it is all fixed. I used a bit of silicon sealant under all of the new components to help anchor the new components to the board. Note, I still have to put the jumper back. Without the jumper in the right position the board won't work.

I put the alarm back and all is well. The service theft alarm message went away. I have not gotten a random alarm, but it is too soon to tell for sure. It is March 2010. I will report back in September.




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