1994 GMC K1500 Speedometer Problems - Help??

[Vettepilot]

Well, I've been studying and researching this, and I'm stuck. Help??

As stated, it's a 1994 GMC K1500 4x4 extended cab with 5.7 engine that I'm fixing up and trying to get back on the road.

Latest problem is the speedometer. It is reading far too high; looks like around 35 mph is 55 plus on the gauge. It also sometimes jumps. This is an old, somewhat abused truck that I bought not running. I got it going, but have only driven it on a 6 mile test drive so far. So I know no history; only what it's doing now.

My research indicates three things, I think:

1. This is apparently a common problem.
2. It is often (usually?) the speedo head/gauge itself at fault.
3. 1994/1995 units are different/unique from other models?

There is a "You Pull the Part" type junkyard here, and they have several of them, but not 1994. (Mine has the tach, and these do too.)

Questions:

How do I determine if it is actually the speedo head at fault??

How do I find out which years will fit my 1994?? (The junkyard does not know, and does not accept returns.)

Do these have a finite life?? (The ones in the junkyard have 200, 000 to nearly 300,000 miles.)

Is there anywhere that rebuilds them??

Thanks guys!
Vettepilot

 

[jus10inbrla]

Moonie gage is 88-91

92-94 are same Mechanically. Only difference otherwise is 94 is glass / quartz lense, 92 & 93 are plexiglas.

they cant be rebuilt. Not steppers like later . They are air core, unlike the oil core that can be adjusted On the 95-98

95 starts first year of dash change , but is still a tbi motor . Last yeae of obd1.

 

[someotherguy]

I've never heard of anyone complaining that 92-94 clusters go bad. They might be confusing issues from 88-91 clusters. The jumpy speedometer in yours is most likely tied to the speed sensor, which someone suggested in your prior thread about this.

Richard

 

[Vettepilot]

Umm.. This is the first thread I've made on this problem.

Anyway, most of the ones in my local junkyard are newer. 96, 97, 98. What years will work in my 94? Even if I don't get one from this jumkyard, knowing the year span fitment will help searching E-bay, etc.

Thanks!
Vettepilot

 

[Komet]

Could be the wrong cluster for your tire size / axle ratio, I wouldn't so quickly assume there is a malfunctioning component. Possible diagnostics include figuring out what combo your speedo is calibrated to and comparing that to what you have. You could then calculate the expected waveform for a known speed and send that signal with a multimeter to evaluate the accuracy of the indicated speed. I believe the speedometers can be recalibrated if that's your problem, or you could bypass the DRAC and send the VSS signal to a converter box that you could tune until it outputs the right speed.

 

[Vettepilot]

Since my VSS might be bad, plus I am going to be changing tire size, I went ahead and bought a new VSS with DIP switches. I've heard that bad solder joints on the jumpers on the VSS can cause speed indication problems. So I guess I'll try that board first.

I don't remember; does OBD1 scan show speed? If so, I could run it while scanning and see if that speed matches GPS. If so, that will indicate a bad cluster, right?

I still would like to know which year clusters work on 1994 trucks.

Thanks!
Vettepilot

 

[jus10inbrla]

Umm.. This is the first thread I've made on this problem.

Anyway, most of the ones in my local junkyard are newer. 96, 97, 98. What years will work in my 94? Even if I don't get one from this jumkyard, knowing the year span fitment will help searching E-bay, etc.

Thanks!
Vettepilot

92-94 are same Mechanically. Only difference otherwise is 94 is glass / quartz lense, 92 & 93 are plexiglas.

I answered the question what years u need in the first post

 

[Vettepilot]

Ok, not trying to be difficult here, I just don't think I understand. Are you saying that 92 to 94 are the same, but 95 and up are different and will not work??

I just found a website offering rebuilt ones that supposedly fit 1994 to 1997. I am confused here.

1994 - 1997 GMC Jimmy & Sonoma - Instrument Cluster Replacement

Leader in instrument cluster replacements for GMC Jimmy & Somona. Pre-programmed with your mileage - plug and play! Warranty & FREE SHIPPING.

issautomotive.com

Can you straighten me out on this?

Thanks!!
Vettepilot

 

[jus10inbrla]

Thats corrct. 92-94 are what u need. Make sure the tach is for v8 also.

the 95 up dash is the same, but the 95s wiring is different as it was still a obd1 tbi motor

also the ad u are lookin at is for a sonoma / jimmy, totally different dash than the c/k lineup

 

[jus10inbrla]

GM 16193705 (94) or 16140115 (92/93) is the part numbe you need