Gauges

[Canada4g63]

The tack and speedo are inop in the car i just bought. Does anyone rebuild these?

[Imp558]

that's kind of fishy, I would think perhaps the problem does not lie in the gauge cluster

[55trucker]

I take it that the mystery vehicle is not a Mitsubishi

[Canada4g63]

They turn over when you start the car but once started the tach goes,way over like 7grand and the speedo gets tied up to the tach needle. I believe the step motors are bad in both. No its not a dsm car its,a 1990 a TGP

[55trucker]

*just pullin' your leg*.......

 

what do you see when you just go to *run* ..no engine start

[RobertISaar]

it's safe to call it a common issue, I've rebuilt a couple dozen specifically for that complaint. usually comes with the fuel light and check gages light working oddly as well.

 

these clusters don't use stepper motors(except for the odometer), they're just magnetic air-core gauges, which are fairly robust when the circuit that drives them doesn't have a poor choice of component selection in it. they are susceptible to vehicle angle though, but you're generally not concerned with ~3 or 4MPH accuracy when dealing with a ~25% grade.

[Canada4g63]

Do you offer rebuilds still ?

[digitaloutsider]

that's kind of fishy, I would think perhaps the problem does not lie in the gauge cluster

 

Extremely common. I have never seen a working TGP gauge cluster aside from ones that have been rebuilt by Saar.

[Imp558]

Extremely common. I have never seen a working TGP gauge cluster aside from ones that have been rebuilt by Saar.

Logically with multiple failures we look for a common denominator, I wonder what it is in this case. If the failures are indeed coincidence I suppose the common denominator is simply time. I'm not a big believer in coincidence for the most part.

[55trucker]

How are your troubleshooting skills?

 

all the gauges have a common ground with the exception of the speedo, you can disconnect the circuit from both gauges at the signal source side (ICM for the tach & speed sensor for the Speedo) the ECM controls the signal for the speedo, check for a problem in the wiring first before you condemn both gauges. The issue may be simpler than you think.

 

The pics are for '91, can't see the 90 TGP's cluster being too much different.

 

 

 

[RobertISaar]

Logically with multiple failures we look for a common denominator, I wonder what it is in this case. If the failures are indeed coincidence I suppose the common denominator is simply time. I'm not a big believer in coincidence for the most part.

 

the clusters use  a laser-trimmed resistor(in a DIP package) to calibrate both speedo and tach. the little resistive pad likes to either visibly flake apart and increase resistance or they occasionally do the same without any visible evidence. in either case, I just bypass the pad that is used for the speedo and tach cals.

 

there is at least one more(though I seem to remember 4 total?) resistive pad on that DIP package that is used in-circuit, but I can't remember what it's used for off-hand, though I've never seen  it become  an issue yet.

[White93z34]

I 100% recommend Saar's services. Is the one thing in my TGP that actually works right now.

[RobertISaar]

Do you offer rebuilds still ?

 

yes, though scheduling is going to be a bit rough for a while, we're running at mandatory weekends at work for the next INDEFINITE PERIOD OF TIME and  the last thing I want to do after work is crouching over a PCB for an hour+ reworking it. so, if you don't mind waiting(what is likely to be) a few months, I'd suggest it, otherwise I would have to charge significantly more to make it worth my time.

[Canada4g63]

I'm in no rush to get it fixed because the hud works. It's definitely something that i want to jave working properly

[55trucker]

perhaps you could pick up a spare cluster, I came across a few on ebay a week ago.

[Heartbeat1991]

perhaps you could pick up a spare cluster, I came across a few on ebay a week ago.

It's not worth it.  They charge more for them on eBay than Saar typically charges to rebuild them, and they very likely have the exact same problem.  

 

Saar has rebuilt several of mine.  I wouldn't send mine anywhere else.

[55trucker]

I too have the *cold solder* problem that causes the low level fuel light to glow & the *check gauges* to stay on, I've had the cluster out twice trying trace the pcb on the back could could not find the source.

[RobertISaar]

from the GP clusters I've had in-hand.... all 89-90 UB3 clusters(not the half-digitals, though they wouldn't surprise me) will have the speedo and tach go nuts, it's when, not if. I imagine most have by now.

 

SOME 91-93 clusters have the speedo and tach get out of whack. not all, for whatever reason(I'm not sure if it's a build date related issue or not).

 

 

 

all will have the check gauges and low fuel light issue, at least once, eventually. GM's choice to use whatever the hell lacquer-like conformal coating on  the last ~4" or so of  the board seems to cause issues. 

[Canada4g63]

Do you fix these,saar?

[Imp558]

After a while you'll learn to assume he not only fixed whatever it is but studied it in the process and now knows more about it than it's creator.

[jman093]

I 100% recommend Saar's services. Is the one thing in my TGP that actually works right now.

 

Ditto. All 3 of mine were bad. All 3 were repaired by Saar. While you have the cluster out 4G63, sand off the paint from behind the Intercooled Turbo script on the cluster face and install the missing bulb behind it. Looks nice at night lit up.

[RobertISaar]

Do you fix these,saar?

 

 better than new.

 

After a while you'll learn to assume he not only fixed whatever it is but studied it in the process and now knows more about it than it's creator.

 

figuring out just what driver is used on these clusters for the speedo and tach took hours, if not days of scanning through period-correct datasheets, matching up sample circuits, eventually finding a match, finding superseded versions, finding superseded versions to those, repeat a couple more times, finally find parts that are actually still available, buy a stock of them for the inevitable failure of them in the future....

 

then repeat the process for the odometer driver.

 

and then the IC that controls the check gauges and low fuel lights(that one was a lucky guess though and took a whole 5 minutes).  and for  the TGP specific clusters, the IC that runs the boost gauge(another fairly lucky  break).

 

 

then mapping out every single component on all of the PCB revisions I've come across, determining and assigning a  function for  the more critical ones.... I mean, I might  know a thing or two about  them. I've got spreadsheets, images and text documents that are all generated from  my work that an electronic repair shop would have had to pay $$$$ for  back when these were  relevant.

[Imp558]

..... and that's an affirmative to what I said before.