Troubleshooting a Stack ST400 Tach

[snettleship]

Not sure where to post this, so I'll start here. I bought a club ford in 2010 and it has a Stack ST400 (ST400-4105) tach. Seemed to show the correct RPM. I tried to get the Tell-Tale to work but it never did. So, a winter project was to see how to fix this. I replaced the switches with the momentary type with toggles switches, not push buttons and put them right next to each other. Then the debugging started:

- Power ON: Needle goes behind logo then to zero (ok)
- Start car, need responds to RPMs as I would expect (ok)
- Run Self test (Max+Run), needs steps through RPMs (ok)
- Set shift light Max and Run switches work (ok, actually, never knew it had a shift light but I put a tester on the right wires)

Things that are strange:
- Instructions talk about a Green LED and Red LED. I only ever see a Green led behind the logo. Don't even see a red led anywhere
- Power ON reset doesn't work (with Max+Run). When I try it will eventually acts the same as a the self test does above.
- When I power off the car and power it back on, I loose the shift light RPM setting
- Power On and Run to set cylinders doesn't work (must already be set and stay set for a 4 stroke 4 cylinder engine right?)
- Max button doesn't work to see tell tale

The car is wired Battery -> cutoff -> fuse -> instruments. I checked that the proper wires are wired to the proper switches

Any help would be appreciated before I try Stack Co.

[Dick R.]

Try contacting:

http://www.racerpartswholesale.com/

They frequently ship Stack tachs to Stack for diagnosis and service if needed. I don't recall the detail/$$$ but it was reasonable and relatively quick. A common cause of Stack issues, at least for the recording type like mine, is that the hardwired internal battery goes bad after 10 or 15 years.

Dick
CM 85
Raleigh

[snettleship]

Thanks. I was hoping for some magical reset or something I could do myself. I had an aversion to sending something critical on the car to service that I need back to race. But, I have some time, thus the winter project. Glad I could post a question that was responded to by someone in the same county I live in.... (Wake Forest , NC)

[Dick R.]

Scott,

I suspected that you would get a kick out of the Wake County connection.

My Tach didn't have as many problems as yours. It was just getting somewhat "suspect" on recording runs and playing them back. Your problems go beyond mine. However, they sound like ones that are related to internal battery power to "save" stuff in memory. Since I don't use the shift light I don't know if it worked.

I checked my emails to/from Racerparts and the diagnosis charge was just under $70. Repair (battery only) was less than $150 in 2009. I forget whether that included the diagnosis charge.

I think there is a thread on ApexSpeed regarding these problems including some input on replacing the battery (finding the right battery and soldering it in place are required for DIY).

Dick

[snettleship]

Yea, the thing is I don't use the playback at all (well, wouldn't even if it worked since I have a camera and GPS). If it costs something like $250 to repair it I can get a "ST200" or another tach for around $350 new. Things to think about.

[scorp997]

you have an older ST-400 that was made prior to the cylinder configuration and recording (recording was optional in the original units). The 'single' LED was the easiest give away.

I will bet that your rear sticker has something in the 'freq' box, like "4cyl" which will tell you it is hard coded. I have a couple of these and I am in the process of mapping out the DIP pins so I can reconfigure one.

I believe I still have the original owners manual at home for this version, which is different than the current model. Send me an email and I will try and dig it out and send it to you.

[snettleship]

Thanks to John for his advice. I decided to replace the battery with a replaceable battery holder inside the tach. I posted my experience here http://www.apexspeed.com/forums/show...612#post333612

[scorp997]

excellent work, glad it was that simple. I still owe you the manual for it.

I suppose you have already buttoned this up and done? I was hoping to get you to send me a photo or a diagram of the internal jumpers that determine the rpm and cylinder configuration. I would like to post a 'how to' to change the cylinder configs on the older models (6 cylinders seem to be pretty common and relatively inexpensive)

[snettleship]

yes, I can see how the picture didn't do much good. Here's what I see:

O for open, P for Pin


-------- Battery -------

O O P P O O O O O O P O P
O O P P O O O P O O P O O

[Phil Creighton]

I think I have the pin configs from when I was a Stack dealer - I'll look for it
phil

[Motorsport Services]

Not sure where to post this, so I'll start here. I bought a club ford in 2010 and it has a Stack ST400 (ST400-4105) tach. Seemed to show the correct RPM. I tried to get the Tell-Tale to work but it never did. So, a winter project was to see how to fix this. I replaced the switches with the momentary type with toggles switches, not push buttons and put them right next to each other. Then the debugging started:

- Power ON: Needle goes behind logo then to zero (ok)
- Start car, need responds to RPMs as I would expect (ok)
- Run Self test (Max+Run), needs steps through RPMs (ok)
- Set shift light Max and Run switches work (ok, actually, never knew it had a shift light but I put a tester on the right wires)

Things that are strange:
- Instructions talk about a Green LED and Red LED. I only ever see a Green led behind the logo. Don't even see a red led anywhere
- Power ON reset doesn't work (with Max+Run). When I try it will eventually acts the same as a the self test does above.
- When I power off the car and power it back on, I loose the shift light RPM setting
- Power On and Run to set cylinders doesn't work (must already be set and stay set for a 4 stroke 4 cylinder engine right?)
- Max button doesn't work to see tell tale

The car is wired Battery -> cutoff -> fuse -> instruments. I checked that the proper wires are wired to the proper switches

Any help would be appreciated before I try Stack Co.

Install manual and troubleshooting is available on their website: www.stackltd.com/st400.html
If all else fails, give them a call. Found their techs to be quite helpful.

[scorp997]

I think I have the pin configs from when I was a Stack dealer - I'll look for it
phil

That would be EXCELLENT! please post or forward a copy if you find it.
thanks

[scorp997]

yes, I can see how the picture didn't do much good. Here's what I see:

O for open, P for Pin


-------- Battery -------

O O P P O O O O O O P O P
O O P P O O O P O O P O O

Thanks for the update. I will add that to my other configs.

[snettleship]

Thanks for posts regarding the Stack ST400 manual. I have the online copy. As John has pointed out, I guess not all ST400s are alike over the years. The one I have does not have a "Run" light, only the green "on" light. When I opened the rear cover, there was a sticker on there indicating a 18-2-1993 date. I may give Stack a shout and see if they have a "vintage" ST-400 manual (before all this posting online was going on....).

[scorp997]

As for contacting Stack for manuals, here is a link that bypasses the 'user information' questionare and gets you to the online documents.
http://www.stackltd.com/support3.html

[Bob Clark]

We also have the Stack manual's posted on our website for each tach

https://www.pegasusautoracing.com/ad...goryID=STACKGA

[coupequattro]

Sorry to resurrect an old thread, but I have a similar problem...

I have 2 old stack Tachometers, one set to 4 cylinder, one set to 12, and I'd like to reset these to run on a 5 cylinder engine.

First one....

Stack part number 400-0385-12 (set for 12 cylinders). Dated February 1989.
Display format is 0-3k-8.5k

CPU, Battery and Crystal located here

O O P P P O O P O O P O P J1 marker at this end
O O P P P O O O P P P O O

Second one.....

Stack part number 400-048-44 (set for 4 cylinders). Dated April 1990.
Display Format is 0-4k-8k

CPU, Battery and Crystal located here

O O P P O O O O O O P O P J1 marker at this end
O O P P O O O O P O P O O

If anyone could help me decode the information, it would really help my classic rally car project.
Also, does anyone know where the metal strip used to connect the pins can be sourced? (I can make it using discrete wires and pins, but the proper solution would be best I think....

[scorp997]

it all depends on how many pulses your 'tach' signal sends to tachometer per revolution. A 4 cylinder (with points) will give 2 pulses per engine revolution. I suspect your car will only give 1 per revolution, sent by an ECU. If that is the case, you can use a pin configuration I have for a "2 cylinder" 400-048-24 that should work with your 400-048-44 tach.

the pins I have for that tach are:
OOPPOOOOOOPOP
OOPPOOOOPOOOO

You can try this and see if it works for you. Thanks for the 12 cylinder config, I will add that to my matrix - I may yet be able to decode the pins. can you confirm for me that the 12 cylinder engine this went on had 6 ignition pulses per revolution? If it was from a newer engine with an ECU, it is possible that it had 1 pulse per rev and *could* work for you as is.

Good luck and let us know what you find out.

[coupequattro]

The 5 cylinder engine that I have is an electronic ignition system rather than points, but the RPM signal comes from the coil, so I think that it's 2.5 pulses per revolution, or 5 pulses per 2 revolutions. No ECU, it's a mechanical fuel injection system (CIS) and normally aspirated.
I can't answer the question regarding the 12 cylinder unit, it's one that I bought off fleabay.....

[scorp997]

most Bosch systems have a diagnostic rpm sensor that is not attached to the ignition/fuel at all. BMWs have it accessible from the "D" plug on the top of the engine (don't know much about Audis). If you were to use (or add) a sensor that picked up a single pulse, you may be able to use that as well.

[coupequattro]

It's one pulse every time it fires, so 5 pulses per 2 revolutions. There are no sensors in the system, it has a conventional distributor and ignition module (hall effect sensor instead of points, the module just tells the coil when to let go). There is provision for a flywheel sensor, but that would just pick up TDC.

No diagnostic plug, but pin 7/7 on the ignition module outputs the tacho signal as well.

Very simple and basic system, but extremely reliable, as long as there is fuel and sparks it will fire.

By the way, I was trying to send you a personnal message, but it didn't work (new to forum maybe?), could you maybe drop me a line please?

[Jay Laifman]

Does anyone on this thread know how the bezel and case removed? And is it possible to remove the face and replace it?