1997 Taurus starting trick - will not start until whirring noise stops under the hood

[MyTaurus8AChevy]

Originally Posted by shorod

Where did you hear that using a meter to test a germanium diode will destroy it?

Well maybe 'destroy' is not the best word to describe it. What happens is that it completely ruins the diodes sensitivity, basically making it a wrong part for that circuit. This is especially important when testing radar circuits. It's a fairly well know testing procedure. I'll see if I can find anything regarding it on the net for you

[MyTaurus8AChevy]

Well I found this for you. Notice the last line of "Testing Diodes with an Ohmmeter" it says "NOTE:This test should never be used to test crystal mixer diodes in radars. It will destroy their sensitivity." and right under that is says: "An oscilloscope can be used to graphically display the back-and-forward resistance characteristics of a crystal diode."

If I find more on line I'll post it for you

[shorod]

Interesting, thank you for the link. I guess I'll have to remember to use my Fluke 199C from now on to test any germaniums I come across.

-Rod

[shorod]

Ooops, now that I've looked at diagram 2-15 in the link you posted, it looks like I should have kept my Tek 454 scope. I don't think the Fluke has horizontal and vertical inputs.

-Rod

[MyTaurus8AChevy]

Is it a B series or a C series?

[Taurus1997]

Hey everyone:

I said I would post pictures of the CCRM this evening....how do I? I got some really nice detailed pictures. The bottom left of my web page says "you MAY NOT post attachments". What do I need to do to change this so I can post attachments?

Thanks.

[way2old]

Go here and upload the pictures. It is a free site. Then you just copy and paste to have pic here. Just copy the EZ code.

[shorod]

Originally Posted by MyTaurus8AChevy

Is it a B series or a C series?

The Fluke or the Tek? The Fluke is a 199C (2 channel color, 200 MHz BW, and the software to go along with it).

-Rod

[MyTaurus8AChevy]

Yeah that is one suh-weet scope/meter I thought I read where the new B series has those inputs but I'm not sure about series C. I don't allow myself to read too much about those scope meters because I tend to drool to much on my keyboard

[Taurus1997]

Here are the four pictures of my CCRM.

The first picture shows the bottom side of the CCRM circuit board.
The next two pictures show the same top side of the CCRM circuit board.
The last is simply the cover for the CCRM.

I have placed a RED ARROW in each picture where I have confirmed continuity between pin-5 and that particular place on the CCRM circuit board.

This should be interesting what is diagnosed here.









Thanks.

[shorod]

Those photos are very beneficial! It would appear that the diode between pins 5 and 15 was not included (D8). The diode symbol and reference designator D8 definitely indicate this would be for a diode. Have you checked for continuity from the corresponding D8 pin to pin 15? On the component side of the board, the corresponding pad appears to be on a ground trace, which is the function of pin 15, so I'm quite confident that you will have continuity to pin 15. This would indicate that D8 is the diode that shows up in the block diagram, and for whatever reason, was not included in your version of CCRM.

If you want to confirm that D8 would be the suspect diode, check for continuity between one of the four large solder connections for the K2 relay (connections on the underside of the board) to pin 11 and one to pin 18. If all these measurements checkout fine, then your CCRM does not include the diode we've been discussing in the thread on the forum. There are two possible reasons for this, either the diode was left off by accident, or the diode was intentionally not installed. I would expect the latter since at Ford, Quality is Job #1.

If the replacement PCM came from the same donor car as one of the PCM's that you also have as a spare, make sure to use the two as a matched set. It is possible that, as joeh100 mentioned before, the diode has been incorpated into the PCM. If the donor PCM is of a different part number or revision than what you removed from your car, then you should use the CCRM from the same car to be on the safer side.

Thank you for providing those photos!

-Rod

[Taurus1997]

Rod, joeh100, others:

Thanks for ALL your help and time solving this vehicle starting problem. It was nice finding people that would offer their time to help others. I learned A WHOLE LOT too about car diagnostics, testing, and troubleshooting. Taurus1997.

[shorod]

Originally Posted by Taurus1997

I learned A WHOLE LOT too about car diagnostics, testing, and troubleshooting.

That's probably the most important part!

And this thread may possibly help others understand why sometimes when they take their car to a shop for service, it takes longer than initially expected to properly diagnose a symptom that seems rather trivial in the beginning.

For many shops, it's a catch-22. If they shotgun an electronic part and it doesn't fix it, they are stuck paying for it and keeping it on their shelf. Or, if they send the car out the door thinking it's fixed, when really the symptom just chose not to exhibit itself at that moment, the customer will be irate that they just spent $600 on a repair that didn't fix anything. If they properly troubleshoot the problem, the customer bad-mouths them for taking 4 or more days to find the problem. In the process of troubleshooting, they may run into parts that don't seem to match the information from the factory service manual, and as you realized, the CCRM is not intended to be taken apart.

An automotive technician would have a very hard time determining that the suspect diode was not actually installed in the CCRM, unless they were willing to eat the cost of a potentially good part.

I've been on the technician side of that story, it's not fun! I much prefer my current job where I can admit to my boss blowing up a $65,000 piece of hardware and just be told, "Try to be more careful next time" or "Write a procedure to make sure that doesn't happen again."

-Rod