Engine Bad A9L computer?

jrichker said:

@91GTstroked

That is an electrolytic capacitor or what is commonly called, a cap. They have a definite life cycle and after 22 or more years, they start to fail. The failure mode is they dry out because the liquid electrolyte leaks out. Then they burn up or blow the top out of the can that they are packaged in. A clue to failure is the top of the can starts to bulge. When you see one bulging it has either failed or is in the process of Many of the automotive computer repair places will replace all of them as a first step in any repair efforts. The capacitors have a voltage rating, a capacitance rating, a tolerance for the capacitance rating, an operating temp rating and a life cycle rating. They also have a specification for cab size and lead placement

The higher the voltage rating, the larger physical size of the capacitor when compared to one with the same capacitance and a lower voltage rating. Most of the ones used in automotive electronics have a 20-35 volt rating since they are used in low voltage circuits. Using one with a higher voltage rating doesn't hurt anything, but it usually doesn't have any benefits either. There may be a size limitation because of the way the circuit board is laid out. That means there are sometimes limits on replacing the 20 volt cap with a 35 volt cap because it won't physically fit in the space allocated on the circuit board.

The higher temp rating and longer lifecycle ratings increase the cost of a capacitor. In automotive circuits, those are important factors, and the highest rating stands the best chance of lasting the longest and working the best. Most capacitors used in automotive applications are rated at 105° C The typical capacitor used in most automotive electronics is less than $1.50 each.

Some informative help from YouTube…
View: https://www.youtube.com/watch?v=YCSNWi3UHf4


WWW.digikey.com or www.newark.com are good sources for capacitors, resistors and just about any other quality electronic part. Avoid Radio Shack unless it is a temporary repair or emergency situation. Almost all of their parts are less than top quality stuff and a lot of it is just plain junk.


That's the easy part; now here comes the gotcha... The circuit boards are almost all multilayer construction. That means you have to be able to apply enough heat with a pencil tip soldering tool to melt the solder on at least 4 layers and sometimes more. Then you need to have a solder sucker to suck up the solder once it turns molten but before it burns or damages the PCB (Printed Circuit Board). I have been fixing PCB's in computers for 41 years now and it is still a challenge to do it right and not make a mess of it.
The capacitors have a stripe on the side of the can that indicates polarity. Make sure that you match the polarity markings on the capacitor with the polarity markings on the PCB.

Some more help from YouTube…
View: https://www.youtube.com/watch?v=urGB_IUXSIM

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7991LXnSHO said:

At $450, for a rebuilt one -

1989-93 Mustang 5.0 5-Speed A9L Mass Air Computer

1979-93 Fox-Body Mustang Experts! Located near Charlotte, NC our focus is Foxes and we know them better than anyone! We offer brand new reproduction parts as well as NOS (New Old Stock) and even some good used parts. We are on a mission to 'Save the Foxes'.

www.foxresto.com

I would send mine in to be rebuilt at one of the businesses that has fast turn around for about $130, unless you really want a back up.

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7991LXnSHO said:

That’s the one I used. Duck Duck Go EBay or Google has others.

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7991LXnSHO said:

Quick and polite service.

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voodoo18 said:

91GRstroked has the answer. I have used these people. If the computer is good, they will tell you. If it is bad they send it back no charge, just shipping. If you have questions or problems, email them and they will help you figure it out. Good luck.

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