Gauge cluster illumination and grounding

If you look at the factory service manual usually they list all the radio noise suppression capacitors that were installed on a particular car line in the Accessories section (wherever the radio install details are).

Look on page 15-2 at figure 15-3 of the link: 1967 Service Manual Accessories. This changed very little over the years.

 

I used to have the 1970 Olds manual, and yes, I saw that page or those pages (a looooong time ago, I don't even have the manuals any longer), but as far as I remember, no there was no RF choke connected in the fuse block.

 

Here we go with the cluster...as i pulled it out of the dash, there are so many questions:

1) i'll clean the copper-parts and add another ground-wire from the case - is there anything else i can do?
2) when i move the pointers from all 4 instruments around the fuel economy-instrument they get back to this position - is that really how it should be? I guess it's not.
3) is there anything i can measure? As i mentioned before, i'm not that much into electric-stuff

 

So, the cluster-illumination is fixed. Here's what i did:

- removed corrosion from the bulbs, the sockets, all ground-points on the cluster-housing and the circuit board
- added a ground-wire from a screw on the cluster-housing (not one with copper underneath it!)

 

Here's a video of the pointers when the cluster is back in the dashboard with ignition ON/OFF.
Temp.gauge and oil pressure still look mysterious to me. How should it be?

--> https://drive.google.com/open?id=0B81jhOpudqGLbXFrbGRFSXVJajA

 

Good work! The video isn't showing, what do you mean "look mysterious" on that?

 

Unfortunately the video file seems to be too huge to upload or Google has some problems, I don't know.

Ignition ON - Temp and oil pressure 0 (that's OK)
Ignition OFF - pointers slowly move down from 0 to ~40 (oil) and a little bit up to somewhere (temp)

I guess that makes no sense.

 

Ignition on, engine off\not running, the oil should be at 0 and the temperature at whatever the engine is at (cold should be all the way green). The temperature only has ~80 degree sweep, it won't start coming up until the engine as at least 150 or so.

When the engine is on, engine running, the oil PSI should be reflective of the engine oil pressure, same with temperature.

When the engine is off, key off the electric circuit is off so the gauges will just kind of go wherever they want. They'll usually hang out in their last state with a gradual move towards the middle as it does require current through the needle mechanism to make them move anywhere. When the car is completely off don't worry too much about the gauges.

 

Ok thank you very much, I'll go for a test drive to check the gages when the engine is running.

 

I assembled everything and after a test drive i can say:

- gage illumination is good
- gage for temp. and oil pressure is not

I marked the area where the pointer is moving. I'm convinced that the gages are not the problem.
Now things get a little complicated:

The previous owner swaped the engine to a 350 SB from a 1988 Chevy Van.
So now i have the gages of a 1975 Pontiac and the sensors of a 1988 Van. I know that at least the temperature sensor is different, that means the one from 1988 has lower resistance, resulting in a faulty pointer movement.
I guess it's the same with the oil pressure sensor and thats why both pointers are not showing what they should.

 

There's your problem most likely. The sending units. I would check rock auto for the sending units for your wagon. Probably the cheapest place to get them. If they aren't listed under engine then try electrical section.

 

It's not a big problem to get one. The problem is the different size. Oil pressure sensor looks the same, but the temp.sensor for the 1975 400 Pontiac engine is bigger than the thread in the block for the 1988 sensor. I probably can't solve the problem on my own.

 

Oil hole is probably 1/4" while the water temp should be 3/8", both pipe thread.
Look to see if there is an alternate spot to install the temp sensor in a water jacket.
You must have the proper ones in your possession to know they are different sizes?

 

Here is the temp.sensor. The proper one for the 400 Pontiac engine and gages and the old one for the 1988 Chevy SB (the arrow can be ignored). You mean there could be another place for the sensor somewhere?

 

The one you took out appears to be a bit smaller. Is it metric threads? The older Chevy engines had a couple of spots on them that you put a sending unit. The next best thing I can suggest to use the proper sending unit is an inline rad hose adapter. I've used them and they work like a charm. Amazon has them cheap in different sizes but you will have to drill and tap for your size sending unit. This is what I did.