my stepfather was driving my 89 rs 305 today and the oil pressure guage started acting up really bad. gauge went off the scale at anything above idle at idle it dropped to zero. then it was completely inaccurate. i replaced the sending unit. now gauge is all the scale any time engine is running. did the guage go south? i think its screwed, but im not sure. what would be the best way to get a guage working again properly? do the stock gauges fail? should i replace the guage unit. the factory tach already doesnt work. install a mechanical gauge? i have a sunpro aftermarket tach, but i dont like all of these aftermarket gauge jimmy-rigged and i dont like a instrument cluster full of dead gauges. do the stock gauges all start failing around 150k? or do i have a problem somewhere else in the wirring? what do you guys think? engine still runs normally no other problems appear to exist i just want an oil pressure guage that reflects what my car is doing. summit sells a kit for 30 bucks it includes oil pressure gauge, temp gauge, and a volt meter. is that my best bet? mechanical gauges dont lie.

 

When the gauge is pegged all the time, it's usually because of a direct short, which means either the gauge has gone bad, or the hot wire to the gauge is grounding out on something. Check the wires down by the sending unit for bare spots. If they look ok, the gauge has probably gone bad. The stock, 115 mph gauge clusters from the RS cars are dirt cheap on ebay and here in the classifieds. You could probably pick up a whole cluster for $20-$30 and replace the tach/oil pressure gauge. Since the tach and oil pressure gauge are combined, you might have a bad spot in the printed circuit on the back of the cluster, the contacts on the back of the tach have wiggled loose, or have corrosion on them. The gas gauge in my cluster went bad, and it was pegged full all the time. I snagged one from the junkyard for free, replaced it, and it's been fine since.

 

but they do spew hot fluid all over the passenger compartment when they fail....