Cluster swap with some issues...opinions needed

[droppedgmc]

So I recently picked up a new gauge cluster for my 81'. The truck had dummy lights and I wanted oil, w/ temp and volts since im using it as my DD. So I found a new cluster from an 84' diesel. swapped my fuel/ MPH gauge into it. Repined my harness per the schematic. Replaced water temp switch with sending unit. added a "T" with oil sending unit.

The problem is the water temp is reading hot. Motor has new water pump/ T stat and full of coolant. I can grab both hoses and they feel fine. I've tested the T-stat, it opens @ 180°. I've also tried 3 different guages, they all read the same. 225°+.

Also I can't get the oil pressure gauge to read correctly. Its always pinned full pressure. Everything is wiredas per schematic for "gauges".

Could all this be caused because of the circuit print from the diesel? Do I need a gas printed circuit board?

Thanks for any help

[76Charlie]

What motor? where is your oil pressure line going? If it is by the top of the motor like a 350 it reads normal, if you ran the line (like I did) next to the oil filter, then it will read abnormally high, my 454 runs pegged almost all the time

[droppedgmc]

forgot to say my motor is a 250 I6

[Skunksmash]

Just did a similar project on my 87 silverado. Had all those gauges but replaced some of them with better more accurate ones cause the stock ones were irritating me.

In all likelihood your oil pressure sending unit is bad. If your truck is like mine you've got two of them. An upper at the back of the intake and a lower down near the oil filter. My oil pressure gauge was doing the exact same thing yours is, and now that I've replaced both oil pressure sending units, the oil pressure needle reads like its supposed to.

As for the water temp gauge, all I can tell you is the factory one is a piece of doodoo. Mine was telling me my truck as running at 155 degress. It was 30 degrees off lol. Get an infared temperature checker gun (like $12 on amazon) and aim it at your thermostat housing and see what your temps REALLY are. Once your truck gets warm of course. I found out that my truck was running within stock parameters at 187 degrees. Not 155. So I tossed that stock piece of junk water temp gauge and got a digital one and its always accurate now.

[droppedgmc]

I had to add the second sending unit for the oil pressure...guess I need to look up on the back of the head to see if there is another port for it. it's currently T'd off the other

[Skunksmash]

Oh for some reason I was thinking your truck was a 305. My 82 305 had a sending unit at the back of the intake.

[droppedgmc]

Originally Posted by Skunksmash

Oh for some reason I was thinking your truck was a 305. My 82 305 had a sending unit at the back of the intake.

correct...the 305 has the same location as a 350

[droppedgmc]

So I fixed the oil pressure...dropped a new wire from the sender to the gauge cluster. wah lah....works perfect

[Skunksmash]

Nice. Did you do that water

[droppedgmc]

tried that with the water..no change. I'm going to get a different sensor in the morning, i'll report back then

[Skunksmash]

Doing half a cluster swap is a bigger job than I thought. I got it all installed and all the gauges work, but now I gotta take it all back out and fix 6 more problems. The new RPM gauge, the new fuel gauge, and the bright lights indicator all have to be fixed some way cause too much light is coming in around them. The fuel gauge doesn't always work right off, sometimes you gotta tap on the front plastic to make it start to work. So that's going back and soldering all its connections together. (some are only screwed together)

The speedo needle was put on too far ahead of itself, it reads about 8mph fast at any given time. And the new digital water temp readout is too bright. Its way overkill at night so I have to take the factory clear plastic cover and have that spot tinted somehow with limo tint. Ah the joys of hotroddin'. And that's just swapping out 3 of the gauges for aftermarket. At this rate I can imagine another 6 problems if I did the other 3. Ah the joys of hotroddin' but it'll all be worth it when its done.