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Old 06-20-2011, 12:23 PM   #1
JW240
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Default 240 electronic speedometer calibration (1986+)

How to calibrate the speedo of your 240? Here is how.
The speedometer is controlled by a ITT UAF2115 chip. This chip is used in many cars of the same era, including the 7/900 series.
There is a calibration resistor in the cluster that will alter the speed shown by the meter. The trip/mileage counter calibration is not affected by this resistor.



After you have removed the cluster from the dashboard and removed the speedometer unit itself you'll be greeted by this sight. Shown here is the pcb with the chip and calibration resistor and many other components.



The resistor that was in this place was the calibration resistor. I used some thin wire and drilled a hole in the back of the case to mount the resistor outside of the case for easy calibration. When you drill the hole make sure that no shavings are left inside of the cluster that will cause problems later on.
The resistor is mounted between pin 4 and pin 13 (ground) of the chip.



Here the resistor mounted on a screw terminal thingie.

The stock resistor is about 56 Ohm. If you increase the resistance value the speedo shows less km/h or mph. On my car i replaced the resistor for 2 in parallel that are ~61 Ohm iirc and the results are very good. 50 km/h on the speedo is 48-49 km/h GPS and 120 km/h is 119,5 km/h GPS.

Thanks to the Brickboard speedometer calibration article (for 740) and TB member blabla for reminding me of this possibility.

Extra:
ITT UAF2115 Speedometer and mileage indicator chip datasheet
You can change more stuff about how the speedo reads and the mileage counter works, for example changing the amount of pulses needed etc (page 2, grounding/floating/connecting pin 11 etc). Can be handy for people swapping in ABS rear axles or triggering the speedo with front axle abs tone ring etc and when swapping between 12/48/96 tooth tone ring stuff.

Extra 2:
More good stuff here: http://cleanflametrap.com/speedo.html

Hope this helps.
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Last edited by JW240; 06-12-2012 at 06:00 PM.. Reason: series/parallel mixup fixed
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Old 06-20-2011, 07:57 PM   #2
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ugh, would have been nice to know before having to cut teeth and mess everything up.

much appreciated for the write up, Jan.
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Old 06-21-2011, 04:47 AM   #3
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Originally Posted by JW240 View Post
Can be handy for people swapping in ABS rear axles or triggering the speedo with front axle abs tone ring etc and when swapping between 12/48/96 tooth tone ring stuff.
What!? I need to read more about this!
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Old 06-21-2011, 05:36 PM   #4
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wow, awesome article. Will be useful at some point when i am driving a 240 again
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Old 06-21-2011, 06:09 PM   #5
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wow, awesome article. Will be useful at some point when i am driving a 240 again
shouldn't be watching the speedo while autocrossing, plus my speedo works fine.
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Old 06-21-2011, 10:41 PM   #6
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You could probably use an adjustable resistor so that you could adjust the calibration on the fly. Just put some sort of 2 pin connector on one of the blank switch panels.
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Old 06-22-2011, 06:52 AM   #7
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What!? I need to read more about this!
Me too. Can you tell me more about it. Got a pair laying here.
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Old 06-22-2011, 08:19 AM   #8
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Originally Posted by ZVOLV View Post
What!? I need to read more about this!
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Originally Posted by Dirk242 View Post
Me too. Can you tell me more about it. Got a pair laying here.
Open a cluster, look at how pin 2 is connected (ground, connected to +12v or floating) and see from there. I have no idea how it is from the factory. By altering how pin 2 is connected you can alter the speed and mileage displayed/counted by a factor 4, can be enough to go from 12 to 48 tooth for example (depending on which multiplier is selected from the factory).
The front ABS tone rings probably give the same signal level as the rear axle sensor.

In theory it should work. Someone needs to test it.

Last edited by JW240; 06-22-2011 at 08:35 AM..
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Old 06-22-2011, 08:52 AM   #9
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Hey, good info here.

You say that this has no effect on the trip or mileage meter?

That would be good news, because i've been thinking about how to use the 220 km/h speedometer face together with a 200 km/h electronic speedometer. The turbomodels had a cable driven speedo that reached to 220 km/h as standard, but i need to use an electronic speedo from a late model 240 (no speed output gear on the transmission that's being used) in my factory turbo, so in theory i might be able to use that face and the adjust the resistor value to get a correct reading.

BTW, you state that you used 2 resistors in series, but in the picture they are in parallel, are they not? Not that it matters in my case, but anyway.

Thanks for sharing. This is great.
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Last edited by Wagner; 06-22-2011 at 09:07 AM..
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Old 06-22-2011, 05:34 PM   #10
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Hey, good info here.

You say that this has no effect on the trip or mileage meter?

That would be good news, because i've been thinking about how to use the 220 km/h speedometer face together with a 200 km/h electronic speedometer. The turbomodels had a cable driven speedo that reached to 220 km/h as standard, but i need to use an electronic speedo from a late model 240 (no speed output gear on the transmission that's being used) in my factory turbo, so in theory i might be able to use that face and the adjust the resistor value to get a correct reading.

BTW, you state that you used 2 resistors in series, but in the picture they are in parallel, are they not? Not that it matters in my case, but anyway.

Thanks for sharing. This is great.

well, if you want to use the 220 km/h speedometer face, then you probably don't need to calibrate the speedo much . 160 km/h on the speedo was 144 km/h gps on my car.
I'd like the 220 km/h speedo face as well but they are hard to come by (only seen it once) and the finish is different from the 89/90? and up matte finish.

In the datasheet of the chip they state that the calibration resistor between 4 and 13 only has effect on the galvanometer, not the stepper motor for the mileage meter. I never tested it but the trip meter seems to be the same as before I think.

I always like it when there is a simple solution with simple/stock parts for these little issues. No need for complicated stuff.

yeah good call on the series/parallel mixup, must have been late when i typed it
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Old 06-23-2011, 06:03 PM   #11
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Good info, any one adapt an electronic speedo to an early (pre 81) cable driven instrument cluster? Ive got a 79 dash in my 86 240 truck with an M46 from a 700, no speedo gear, but ive still got the speedo sensor wiring in the car. I can get an OD with a cable output, but i dont wanna, lol

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Old 06-11-2012, 06:15 PM   #12
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Old thread -- perhaps we can revive. Is there a late model 120 mph electric speedo that I can transplant into my '82 cluster to replace the cable driven unit?

JW240 - a few things; go slow with me and talk like I'm a second grader. The unit in the first 2 pictures above looks entirely different from the unit you actually worked on. What am I missing there? Which one is an electronic speedo for a 240? Also, in your written comments you say you hooked up 2 resistors in series; but from the picture (with the 'screw terminal thingie') 2 resistors appear to be hooked up in parallel. Do my eyes deceive me? Last - is there another resistor that can be used to adjust the odometer accuracy? Is there a way to alter the odometer reading? I need to ADD miles to mine; when the 85 mph speedo it came with was swapped with a 120 mph unit -- the new speedo had about 48,000 fewer miles than the original. Us Volvo owners are proud of our high miles....

The good news about this is if it will work, I can hook the whole thing up temporarily in the car while I'm driving, calibrating, checking against GPS, etc. And once I get it right - then I can transplant into the cluster.
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Old 06-11-2012, 11:01 PM   #13
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love the info... great work.
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Old 06-12-2012, 06:12 PM   #14
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Originally Posted by turbojose View Post
love the info... great work.
Thanks!

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Originally Posted by M.H. Yount View Post
Old thread -- perhaps we can revive. Is there a late model 120 mph electric speedo that I can transplant into my '82 cluster to replace the cable driven unit?

JW240 - a few things; go slow with me and talk like I'm a second grader. The unit in the first 2 pictures above looks entirely different from the unit you actually worked on. What am I missing there? Which one is an electronic speedo for a 240? Also, in your written comments you say you hooked up 2 resistors in series; but from the picture (with the 'screw terminal thingie') 2 resistors appear to be hooked up in parallel. Do my eyes deceive me? Last - is there another resistor that can be used to adjust the odometer accuracy? Is there a way to alter the odometer reading? I need to ADD miles to mine; when the 85 mph speedo it came with was swapped with a 120 mph unit -- the new speedo had about 48,000 fewer miles than the original. Us Volvo owners are proud of our high miles....

The good news about this is if it will work, I can hook the whole thing up temporarily in the car while I'm driving, calibrating, checking against GPS, etc. And once I get it right - then I can transplant into the cluster.
You are right about the series/parallel mixup, fixed that.

Not sure if i understand you correctly but the unit in the first 2 pics is the speedo unit itself, pulled from the cluster. You can slightly see the face plate too. The 3rd and 4th pic are taken with the cluster assembled again of course.

I do not know of a way to affect odometer reading with this chip, but it has been a long time since i have read the datasheet. Maybe.

Setting the odo higher with the speedo unit removed from the cluster can be done quite easily, the dials-numbers can be rotated if you are careful. At least, thats what i´ve done to some speedo´s that i took apart.

One thing i realized after looking at the pics is that a small piece of shrink wrap to cover the resistor(s) isnt a bad idea, the exposed wire could make a short if the screw terminal thingie accidentally comes loose from the cluster.
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Old 06-12-2012, 07:30 PM   #15
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Thanks JW -- we'll see where I end up!
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Old 06-09-2017, 03:13 PM   #16
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Planning to do this, do you happen to still have the pictures? Atleast the one that points out the right resistor do change.
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Old 06-10-2017, 07:53 AM   #17
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I still have them, need to re-host.

But wont have acces to the pics this week. Maybe Art's site can help you with the chip pinout, you can trace it. In a few weeks i can have the pics up again.
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Old 06-14-2017, 07:23 AM   #18
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I still have them, need to re-host.

But wont have acces to the pics this week. Maybe Art's site can help you with the chip pinout, you can trace it. In a few weeks i can have the pics up again.
Would be perfect if you could rehost those pictures. Would really make my life easier!
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Old 07-03-2017, 02:46 PM   #19
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I still have them, need to re-host.

But wont have acces to the pics this week. Maybe Art's site can help you with the chip pinout, you can trace it. In a few weeks i can have the pics up again.
Would it be possible to upload the pics this week?
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