Modules sent in for repair have common problems addressed to improve reliability. In one example, a body computer would lock up about once every 5,000 miles because of a voltage spike caused by relays turning off. The fix was to replace the relays with ones with the missing spike-suppression diodes so those spikes were less likely to occur, and to replace the body computer with a revised one that had circuitry added to make it immune to those spikes. Because that was a significant difference in the new computer and since it addressed a known issue, it got a new part number. This was a two-pronged attack. If you found an older computer without those revisions, it would still work, but to work reliably, you would have needed to have those updated relays too.
Ford has had a lot of trouble with their "GEM" modules failing from corrosion from windshield leaks. Repairs did not address the leaks. The repair was just to install a new module with one that has a rubber weather seal in the connector to lessen the chance of that corrosion forming on the terminals. The addition of that seal warranted a new revision number, but the older version would work exactly the same.
Another typical example would be out of one hundred modules returned for repair, eighty were found to have the same failed transistor. The repaired modules and those currently being built would likely have a beefier transistor installed to prevent that common failure. The only way to know if you had a module with the better transistor would be by looking at the part number.
One of the two following paragraphs is right, and the other is my mistake. I cannot remember which one is right:
In Ford part numbers, two of the digits and letters denote the model year that part was designed for and was first used. If that same part is used in the following years, those two digits could remain the same. You might find a head light switch in a 2008 model with a part number that shows it was built in 2006, for example. That does not mean that part was built in 2006. It means that part was first used in 2006.
In Ford part numbers, two of the digits and letters denote the model year that part was built. Even if there are no design changes or revisions in later years, those two digits will change to the next year in the part number, then they will keep making that part the same way. When you buy a replacement part, the year it was made has no relevance.
Three or four other digits are for that specific part, and those do not change very often. Here is a short section of a listing I compiled for Ford radios for use at old car show swap meets:
F87F-18C868-AB 1999 Mountaineer
F87F-18C868-AE 1998 4 dr Explorer
F87F-18C868-CE 1999 Explorer
XF2F-18C868-AC 1999 Explorer
XF2F-18C868-AD 1998 Explorer
XL2F-18C868-AB 1999 F350
In this case, the "1987" in the first three part numbers means that part number was first assigned in 1987 models, but you would find that same part number in those three 1999 model trucks. If I remember correctly, the "F2" in the last three part numbers stands for some major design difference starting with 1992 models.
The "18C" is found on every radio with a CD player. The "868" means it is an AM/FM/CD/cassette combo radio. All six of these radios look exactly the same, plug in exactly the same, and operate exactly the same way. The two letters at the end denote very slight differences in a few parts in the output circuitry to tailor that radio's frequency response to the shape of the vehicle's body. The only way using the wrong radio can cause a problem is if you are a HIFI purist and you think you can tell the very subtle differences in tone response.
Every other CD - radio model will still have the "18C" in its part number. The next three digits will be "815" if it is an AM/FM/CD radio without cassette.
Someone will probably come along and correct me on these points, which is fine. I just used them as examples of why you will find a perfectly acceptable replacement part that has a different part number. In the case of Chrysler parts, particularly computers and electronic modules, the part number will be followed with "-AA" to denote there is some update or revision to address or prevent some problem. When a second change or improvement is introduced, the part number will end with, "-AB". These changes can be as tiny as one connection was hand-soldered after the board went through an automated soldering bath. In my world of TV/VCR repair, a large percentage of repairs were due to broken solder connections ten to fifteen years after that product was manufactured. Automated soldering puts just enough solder on the joint to get the job done, ... For now. That solder moves over time just like breaker points used to become pitted over time from repeated arcing. Hand-soldering practically eliminates the chance of that happening. In Chrysler's world, hand-soldering one connection is enough to get one level higher revision number. You might find a replacement module has a revision number up to "-AF" or "-AH", but any of those versions will work in that application.
Friday, March 30th, 2018 AT 7:29 PM
