If you have a Ford vehicle dated somewhere in the mid 80s to mid 90s you probably have a TFI ignition system. You have probably had to replace the ignition module at least once too. Lets take a look at one on its last legs. It was removed while still working, but it wasnt working well. (the timing would jump all over the place) This unit may have stopped working at any time!!

The TFI module is usually found under the distributor. WHY i do not know.

For some reason ford decided to mount the ignition module right under the distributor. Sure, it is convenient to get to, but that place gets HOT. The module's purpose is to fire the ignition coil. It gets its "base" signal from a sensor in the distributor. This signal is cleaned up and passed to the engine computer, which then sends a signal back to it that tells the module when to fire the coil. (if no signal is received from the engine computer, the module uses the signal from the distributor) The TFI module is a piece of electronic equipment. Electronics and heat do not mix. Why did Ford mount these things in such a hot place?

Just the module...

If you have one of these, its not a bad idea to pull it off once and awhile (every year or so is good), clean the mounting surfaces, inspect the module, and re-seat it with some fresh heat sink compound. Remove the two bolts on the front (7/32) slide the module DOWN to disengage the 3 spade connectors at the top. Installation is exactly the opposite. It may be useful to loosen the distributor hold-down and twist the distributor for easier access. It is not necessary to remove the distributor from the engine.

Distributor with the TFI module removed

close-up

Inside the TFI module

The front cover will pry off. Use a thin screwdriver and carefully pry it out. Be careful not to poke the film inside by accident. Do not touch the film.
The image above is of an overheated module. A GOOD module will have no bubbles. Notice the bubbles around the edges the large one at the bottom. If you module develops these, start thinking about getting a spare. I've been told that aftermarket modules dont last as long and that the OEM ones will last longer. With the high heat (65C and higher) I wouldnt want to take the chance with a cheap aftermarket module.

Its a good thing Ford dosent make computer CPUs or heatsinks

For some reason, the mounting surface on the distributor was very rough. I was thinking of lapping it but i dont have the tools nor the desire to pull the distributor. Oh well. Ford reccomends at least 1/32" thick layer of thermal compound. This must be why.
Those of you who are concerned about the heat, there are alternatives. Ford moved the module to a heatsink bolted to the firewall or by the radiator. Unfortunately, these modules do not have the same pinout as the open bowl style shown here. Oh well. In theory, the module can be adapted, but I'm not going to risk a couple hundred dollars of parts to experiment. A $4 heatsink and some connectors from a local electronics surplus store works just fine. More on this later after i've tried it for some time.