Speedo and tach problems

so the speedometer and tach in my '92 RMW (vehicle has close to 200k miles) have been acting up since before i bought the car. they will both occasionally work or sometimes only one will work. once the car has been warmed up and running/driving for about half an hour or more they will both bounce around and flicker a bit. occasionally the speedometer will peg itself at like 130 km/h and stay there even after the car has been shutoff. the cruise control does work, this tells me its likely not the vss but a bad ground. Where do i look for a bad ground?? at the cluster? at the PCM? no idea where i should go next.

FRED,where are you?Probably past his bedtime anyway.Ben,my tach sticks too and the guys say
its the circuitry in the cluster but am sure there will be some knowledgeable help here anytime.
Jim

First I would try pulling and replacing the cluster, just to see if it is a dirty pin.

If not then, I would try replacing the circuit board on the back of the cluster. It is the same as the OCC, 91-93 RMS and RMW. Check all your bulbs while you have it the cluster out. You may have a couple of different bulb placements if changing car types, but it is marked on the board which light is for which car.

It is not a killer job. You have to remove the lower access panel, dash front, and then you can access the cluster. There should be 6 screws under the edge of the pad, one above the brake release handle and one beside the left lower corner of the glove box (all 7mm). You would be wise to remove the glove box door to get the dash front past the stop. You also must put the steering wheel in the full down position, and remove the tilt lever, put the gear shift in low. The dash should pull off provided you have the top edge cleared at the pad.

4~6 7mm screws hold the cluster, and remove the clip for the gear position indicator from the left side of the column. There are 2 connectors which will probably give you a little fight to get them off.

Removing the back of the cluster requires removal of ALL screws on the reverse (5.5mm I think), and gently pulling the circuit board off of the pins for the gauges. The odometer is plugged into the board on the inside (it probably has different gearing from the US version.

Practice on the donor to make it easier on yours. If you need a cluster, I have a couple for sale (US/English not metric). The boards should be the same for both, the only difference is the odometer, and the front markings. If you can find a metric cluster try it first.

I drove 1200 miles with a speedo not working, and it was the circuit board. With both not working, the most likely part is the board.

thankya fred! Jim and i were worried you may have already gone to bed . gonna print off your post so i have something to go by while im out there. sounds like a long job. whenever i take apart old dashes they never seem to go back together perfectly.

Benn:

If you need a new cluster, I am in the process of taking a 91 apart to take off to the JY. It has a good cluster and would be more than happy to pull it for you. It is a US cluster but has the metric markings. ODO is in miles.

I'm south of Ottawa and can get it to you. Removal only takes about 1/2 hour unless your in Eastern Ontario working outside. All jobs take about 15 minutes longer for every 10 degrees (C) colder than summer.

Bill

Make sure you remove the access panel under the steering wheel before you remove the dash, or you will break the tabs along the top of the access panel. If you break the tabs, I will look for a good one for you. They are often broken. What color is your interior?

i have a tan/cloth interior Fred, and thanks for the tip! I'll try my best not to bust any of the tabs.

Bill; I'm located in Kingston On. if i can I'd like to get a metric cluster but as luck would have it there are absolutely NO roadmasters in any wrecker in my area so I'll keep your offer in mind. your right about the temperature thing, its flippin COLD out today!!! -10C. makes ya feel thankful for a garage!

I'm gonna go out today and mess around with it. I'll try taking it out and re installing it. hopefully that'll yield some sort of positive result.

Ben.

I ,have a metric tbi cluster on the shelf out of a 93 rmw in london

The mileage is easy to reset, or you can move your original odometer to the replacement cluster. You have to pull the front off of the cluster (you do not have to remove the pointers) to swap the odometer.

Victory! just got back from a test drive, all gauges are working perfectly now! it was just a matter of removing the cluster, taking it apart, cleaning some contacts and then putting everything back together and reinstalling it. hopefully the cluster won't be giving me any issues for a while. now that the speedometer is fixed i think driving this car is gonna be alot more enjoyable. thanks again for everyone's input and part offers.

A cheap fix is always the best fix. These cars are getting older, and can suffer from corrosion in all kinds of areas.

Free fix is the best fix by far!
Jim

well, that was short lived . im thinking my cluster must be fried. it worked for a bit again and now back to where i started. when i had it all taken apart i noticed an area of discoloration all around a resistor near the tach portion of the board, looks like it got pretty hot at one time. i have found a working metric cluster on ebay.

You should try a circuit board replacement before you spend the money for one on ebay (depending on the price). The boards should be the same for all the 91-93 clusters with the same dimensions/instruments.

I do not know the value of the resistor(s), or I would tell you to try replacing them.

I've had the same issue with the tach on both my '91 OCCs. I've just been too lazy to pull it all apart to fix it, as the speedo is still ok. One of these days......

I have at least three clusters in the garage too... none of which has been tested

heres a happy update. i ordered a cluster off ebay from a wrecker near hamilton on. i got the cluster today, switched over the odometer units with my original one. installed it and buttoned everything back up. everything on the cluster now appears to be working perfect. crossing my fingers hoping this fix will hold out long then the last.

Just for grins, you should swap the circuit board on the old cluster with a generic board from a RMS, RMW, or OCC, and see if it works. Keep the metric face and odometer in the cluster. If it works, you have an extra cluster for cheap, should yours go down again.

I would have swapped the circuit boards and tested it just to see if it was the board. If the board worked with the old cluster, you would know what the problem was, and could fix the old cluster for a spare. You found out just how difficult it is to get another one.

good idea fred. i do plan on keeping my old one, just like you said if this one goes down i'll have another; hopefully at that point i'll be able to get 1 working one out of two broken ones. my "new" cluster had the same discoloration around the same diode on the tach portion of the board so i guess its pretty normal for them to get quite hot in that area. also my old cluster had been stuck at 60 ever since shortly after i reinstalled it. when i took it apart last night, i noticed the speedo needle was very stiff and did not want to move freely. could it be the little motors that had gone bad?? i guess a circuit board swap would tell us that. thanks again fred for help and to others who've chimed in. i can disasemble the entire front dash in under 10 min. with NO broken tabs i might add!

I appears that the prior owner may have tried to fix the cluster, or you laid it down on the face without knowing the consequences. If you push the pointer on too far it will stick. Exprience is a good teacher. You may be able to pull it off a little and it will free up. A fork under the hub is a good way to get them off. I would also put a piece of paper or cardboard under the fork so that you do not mark the front of the cluster display. You may have to put it on at a different location on the hub. The shaft of the motor is square, so it will stay where it is placed. I have some gauge motors if you need one. The speedo and tach are self zeroing, and do not need a specific pointer placement. The other meters must have a correct pointer placement, or they will read incorrectly.

When I painted the backs of my pointers on my cluster, I put the tach and speedo pointers on too far, and they stuck and jerked around. I loosened them a little...as in...put them on with less effort, and they worked fine. You could put a little CA on them to get them to stay on, as an alternative.

I think I can take the dash apart in 8 minutes. If you ever have to take the pad off, remember the two screws in the defrost vent opening.

While my speedo is fine,every since I changed my ignition module to an aftermarket brand the
tach reads about 1000 RPMs fast all the time.This is according to my code reader.
Jim

is it normal for my oil pressure guage to um fluxuate from 20ish to 60 depending on rpm? i have not seen a guage do this i have replaced the oil pressure sending unit oh and my speedo resds 10 mph faster than my gps once i get over 30 also i have not seen my tewp get higher than 220 but thats a good thing lol. i am hovever installing a 160 degree thermostat sunday with a new rad hoses transmission lines ect

roadmastercouple wrote:

is it normal for my oil pressure guage to um fluxuate from 20ish to 60 depending on rpm? i have not seen a guage do this i have replaced the oil pressure sending unit oh and my speedo resds 10 mph faster than my gps once i get over 30 also i have not seen my tewp get higher than 220 but thats a good thing lol. i am hovever installing a 160 degree thermostat sunday with a new rad hoses transmission lines ect

On a 92, you should not mess with the thermostat temp range. It will screw up your gas mileage and affect the closed loop function of your computer.

The oil pressure will go up and down depending on the engine speed. The range you have noted is normal.

The speedo error could be a dirty contact, or the circuit board on the back of the cluster. You can use a circuit board from any 91-93 RMW/S or an OCC (if you canibalize an OCC, send me the remaining parts). You may have to move a few lightbulbs to make everything work.

Yeah I wouldn't install a stat that low in a TBI 350... from what I understand you should stick to the stock temp.

and what is the stock temp may i ask?
is there a better brand than oem the one i ordered from summit is a hypertech 1000 160 degree. i am replacing my radiator and hoses today so ill just get 1 from autozone?

Stock temp is 195. A 160 will kill your gas mileage. If you go into the Engine section there's a recent thread on this.

This is a great thread: https://gmlongroof.4umer.com/t5367-l03-running-cold lots of info concerning your topic mike. Nick, (phantom 309) wrote up a great explanation for us, its about the 17th post down i think.