Hey everyone,
So Ive begun the process of fixing the electrical in my 1974 corvette and have run into a few snags that I was hoping to get some help on. Any information would be a great help.

First I installed a a new oil pressure gauge due to the last one having the issue of moving when car is running but the needle being in the wrong place. However when i changed the gauge the new one now just immediately moves to the 3 oclock position and remains there no matter what, engine running doesn't change it. I cant figure it out?

Second Im installing a new radio and found a constant power but would like to know if there was a keyed power and where one would be from the old radio.

Third I found this weird box behind the passenger side dashboard with 3 pairs (six total) of matching color wires coming out but connected to nothing. I have no idea what it is?




Finally this two lead plug I found on the passenger side. Does anyone know what it goes to?





Agian thanks for any help you can give.

 

74 uses a unique oil sender unit that is screwed into the block "......a wire passes to the gauge .

I never seen an oil gauge from a 74 go bad. That's why they ate plentiful ..LoL nos .

I would suspect the oil sender first .it probably has defective internal blatter ......screwed up inside won't read correct."....doubt it can be fixed....I think it sealed .

I have not seen much failure in that item either

I can tell you I ve seen Nos GM oil sending units on eBay ...they are pretty pricey ...as they fit a lot of muscle cars..and are wanted..don't know if a repop is available ....it's an odd looking unit , looks like a Bunn coffee maker inline water filter

Maybe you can find a used one from a parted out 74 car

 

The weird box you found is the factory radio "amp".

 

Ok ill investigate a new sending unit of the oil pressure.
It is an amp thats what i thought it could be. Any knowledge on which wires are which?
Thanks for the help

 

Oil gauge test:
With the key 'ON':
Remove the wire from the sender and the gauge should read HIGH
Ground the wire and the gauge should read LOW.

Picture two is the connector for the tone generator (buzzer).


Keyed power for your new radio:
Run a new wire from the fuse box port marked 'ACC' to the radio.

 

Ok thank you for your help. Ill try that test to find out if its something I wired wrong or is the sending unit is bad.

 

Heres a schematic for your 74 Stingray:
https://docs.google.com/viewer?a=v&p...TRkNTFkY2E0NmM

 

The oil pressure gauge you purchased, was it the new reproduction? If so, did you install the resistor on the new gauge. If you did, remove it.

If you didn't then follow along.

A oil gauge pegged to the rivet at 3 o'clock is a gauge that is missing ohms input. You have power and ground but no ohms. So go to the sender and pull the wire off, then ground the wire and see if the gauge goes to O oil pressure. If it does then the wiring is fine in the car and the issue is the sender. If it doesn't you'll need to test continuity from the end of the wire (at the sender) to the back of the gauge. If you have continuity then you have a gauge issue, if you don't you have a wire issue between the two and the bulk head connector would be the first place I'd start. Test continuity from the sender to the bulk head connector first, then from the bulk head to the gauge.

The oil pressure gauge is a twin to the fuel gauge, both operate on a scale of 0-90 ohms with 0 being empty or no pressure and 90 being full or full pressure. The only difference in the two is the dampening oil inside and the winding. The oil pressure gauge is way more responsive than a fuel gauge.





You can use this fuel gauge video as a diagnostic tool for oil pressure gauges.


The yellow and black wires are you seat belt warning buzzer wires and the yellow wire to the original radio is your power (switched) voltage to the radio.


Willcox

 

Follow Willcox's advise!
Yes the yellow wire from the original radio connector is the one to use.
I plead temporary insanity for telling you to run a new wire. I must have had my 'bubba' hat on.

 

It's called a convector. It is not needed with modern radios. Take it out.