240 Speedo or Cluster?

[n. rippe]

Good day T-Bricks!

My 1990 240's speedo misbehaves. It didn't work when I purchased the car. I checked and cleaned the wiring at the diff. No change. I tightened/pinched the connections at the back of the speedo and that made it work most of the time. In the morning, it can take 20-30 minutes before coming on. If I bang the dashboard repeatedly (RAGE) I can get it to come on. Once it's on it stays on. Last week I pinched the speedo connections because it was getting ridiculous. It worked perfectly for a few days then went back to taking a long time to come on in the morning.

Based on the behavior I described above, is this an issue with the speedo itself or is it the cluster? I'm wondering if a JY cluster with less miles might solve my problems. What else can I do besides pinching the connections to make this thing work properly?

 

[BigMatteson]

YEAR?
I ASSume it's the '90 in your sig? You may need to pull the wires and re-solder them. It sounds like the connections are poor and it needs some re-working.

 

[n. rippe]

YEAR?
I ASSume it's the '90 in your sig? You may need to pull the wires and re-solder them. It sounds like the connections are poor and it needs some re-working.

Yes, the 1990. What would need to be re-soldered? The wires themselves look great. Nice and healthy.

 

[cleanflametrap]

Based on the behavior I described above, is this an issue with the speedo itself or is it the cluster? I'm wondering if a JY cluster with less miles might solve my problems. What else can I do besides pinching the connections to make this thing work properly?

If I had this symptom - remedied by "percussive maintenance" - I would have done what you already have done, then replace the gauge. I've already had the experience of finding a cracked circuit board (gauge, not cluster) and component lead solder crack (ring round resistor lead on solder pad) with the same results. So depending on your patience with circuits and what-not, you could try to fix your gauge or put another in there with the same K-number on the front. The patience angle pays off if you like to keep your odometer reading. The swap method is better to confirm the nature of the problem.

If you had a problem in the cluster itself, more symptoms than you've mentioned would result, because warning lights and the other gauges get their power source through the speedometer gauge plug.

 

[professor245]

Check ground wire.

 

[professor245]

If you had a problem in the cluster itself, more symptoms than you've mentioned would result, because warning lights and the other gauges get their power source through the speedometer gauge plug.

Exactly, so my thoughts are,
-low signal from the sender (wiring)
-bad ground for ground wire from the speedo-sender, so when you pull the cluster and pinch the wires you accidentally (by moving wires) get ground/signal for a while.

 

[n. rippe]

If I had this symptom - remedied by "percussive maintenance" - I would have done what you already have done, then replace the gauge. I've already had the experience of finding a cracked circuit board (gauge, not cluster) and component lead solder crack (ring round resistor lead on solder pad) with the same results. So depending on your patience with circuits and what-not, you could try to fix your gauge or put another in there with the same K-number on the front. The patience angle pays off if you like to keep your odometer reading. The swap method is better to confirm the nature of the problem.

If you had a problem in the cluster itself, more symptoms than you've mentioned would result, because warning lights and the other gauges get their power source through the speedometer gauge plug.

Thanks. I don't have any experience with soldering so that's not really an option. I'd need to find a speedo with over 300k. There's no way I'm going to go back in mileage.

Check ground wire.

One of the first things I did. Checked and cleaned.

 

[cleanflametrap]

Check ground wire.

Yes.

http://cleanflametrap.com/speedoDiag.html

 

[n. rippe]

Exactly, so my thoughts are,
-low signal from the sender (wiring)
-bad ground for ground wire from the speedo-sender, so when you pull the cluster and pinch the wires you accidentally (by moving wires) get ground/signal for a while.

If was a ground issue than why does smacking the dash "fix it". Temperature definitely has an effect on it. When I drive home in the afternoon it works fine.

 

[professor245]

If was a ground issue than why does smacking the dash "fix it". Temperature definitely has an effect on it. When I drive home in the afternoon it works fine.

Exactly, when you hit it you make ground (presumably) and after some driving (bumps etc...) ground/signal connection gets lost.

Just run two new wires from the sender and hook them up, you don't need to tuck them in, run them across the cabin and see if it helps, that way you can see if it's wiring, make sure you make good ground for ground wire from the sender.

 

[n. rippe]

Yes.

http://cleanflametrap.com/speedoDiag.html

Thanks, Art. I followed these instruction a while back with the exception of using a 9v adapter. Resistance at the junction box checked out fine. Pinching the connectors worked for a little while (even in the morning). I'm wondering if the thing isn't coming loose while driving.

I should add that the speedo will work in the morning for about 5 minutes before needing percussive persuasion.

 

[n. rippe]

Exactly, when you hit it you make ground (presumably) and after some driving (bumps etc...) ground/signal connection gets lost.

Just run two new wires from the sender and hook them up, you don't need to tuck them in, run them across the cabin and see if it helps, that way you can see if it's wiring, make sure you make good ground for ground wire from the sender.

I want to say that the resistance at the connector was the same as the resistance at the junction box. Can't remember if I checked that but will recheck. If the values are the same then would rule out any bad grounds, correct?

 

[n. rippe]

Update

I picked up another cluster from an 87 for cheap. This cluster does not have the Service reset button, my original cluster does. I swapped the odometer only into the new speedo/chip. Had to remove the reset button stuff off my odometer in the process. It now works EXCEPT it reads 6 mph too fast at 34 mph, so, 34mph = 40mph on the speedo (verified with my phone's GPS). I don't know if the difference is consistent across all speeds just yet but will after my morning commute.

The speedo off the 87 is a K10042 unit just like the original. Did I miss something? I was under the impression that so long as I swapped the same model number I wouldn't have these issues.

 

[cleanflametrap]

The speedo off the 87 is a K10042 unit just like the original. Did I miss something? I was under the impression that so long as I swapped the same model number I wouldn't have these issues.

I can see why you'd get that impression:

From post 4: So depending on your patience with circuits and what-not, you could try to fix your gauge or put another in there with the same K-number on the front. The patience angle pays off if you like to keep your odometer reading. The swap method is better to confirm the nature of the problem.

Anyhow I stand by that statement. The K-number refers to the counts per mile, so unless you changed tires (drastically I might add for 15% error) the two gauges should respond the same.

Now, you said you changed guts inside to keep your orig. odo? Did the new gauge's meter come along with it? Those are matched to the resistors on the board choosing the current and part of the model number.

 

[n. rippe]

I can see why you'd get that impression:



Anyhow I stand by that statement. The K-number refers to the counts per mile, so unless you changed tires (drastically I might add for 15% error) the two gauges should respond the same.

Now, you said you changed guts inside to keep your orig. odo? Did the new gauge's meter come along with it? Those are matched to the resistors on the board choosing the current and part of the model number.

Yes. I mated my original odometer with the circuit board from the new gauge. Since the new cluster doesn't have a service reset light, I had to take the the reset button circuit board off. There are differences between the old circuit board and the new one so I can't say I'm totally surprised.

Do you think I could resolve the issue by putting the odo that came with the cluster in, instead of my original? I could always force the numbers to reflect my current mileage.

Also, the odo is counting miles correctly dispite the speedo being 15% too fast.

 

[cleanflametrap]

Yes. I mated my original odometer with the circuit board from the new gauge. Since the new cluster doesn't have a service reset light, I had to take the the reset button circuit board off. There are differences between the old circuit board and the new one so I can't say I'm totally surprised.

Do you think I could resolve the issue by putting the odo that came with the cluster in, instead of my original? I could always force the numbers to reflect my current mileage.

Also, the odo is counting miles correctly dispite the speedo being 15% too fast.

You said the magic words. The fix is for you to change a resistor value. The resistor is the galvanometer current adjustment resistor connected to pin 4 of the 2115 chip. It is the one that is around 51 ohms usually, and the one that matches the board to the meter. Compare that resistor to the one in the other board. Swapping just that might do it.

The real question is, did this replacement solve the percussive maintenance requirement? Is the intermittent seemingly gone?

 

[n. rippe]

You said the magic words. The fix is for you to change a resistor value. The resistor is the galvanometer current adjustment resistor connected to pin 4 of the 2115 chip. It is the one that is around 51 ohms usually, and the one that matches the board to the meter. Compare that resistor to the one in the other board. Swapping just that might do it.

The real question is, did this replacement solve the percussive maintenance requirement? Is the intermittent seemingly gone?

It did fix the percussive maintenance issue. The new setup works flawlessly except for the fast speedo of course. Still gotta learn how to solder though! Wish there was an easier way.

 

[cleanflametrap]

Amazing. I was just about to modify my reply after re-reading the thread and seeing that about soldering. I'm going to have a look at a gauge and see if it is practical to swap just the meter part, instead of the meter with the odometer complete (board only). That might be an easier way.

Edit: I looked. Not practical. You'd be better off re-setting the odometer, which is more fiddly than it looks at first sight.

 

[TrickMick]

It did fix the percussive maintenance issue. The new setup works flawlessly except for the fast speedo of course. Still gotta learn how to solder though! Wish there was an easier way.

see: http://forums.turbobricks.com/showthread.php?p=4345637&highlight=soldering#post4345637

post # * 12 * .... it has a couple of *GOOD* URL'S in it...

soldering is NOT rocker surgery *but* it DOES require a modicum
of PRACTICE....get it right and you'll be golden the rest of your
natural life... (we'll skip the UN-natural bits so we don't scare the horses!)

 

[ZVOLV]

Thanks. I don't have any experience with soldering so that's not really an option. I'd need to find a speedo with over 300k. There's no way I'm going to go back in mileage.

Take a pick and slide the numbers to the left and change em.