Sending units

[Rattler12]

Are the oil and H20 sending units the same for gauge vs idiot light setups?

[Irish_Alley]

no, one will switch on or off at a certain psi or temp and the other will give a constant reading and the sending units should be about the same year as the gauges to give a accurate reading

[hatzie]

Short answer is NO.

All 73-91 square body oil pressure senders and gauges are 0-90Ω just like the fuel gauge.  The oil pressure sender can be had in 0-60, 0-80, & 0-100 PSI ranges to match whatever gauge you have.  Since the top pressure is always 90Ω... If you get the wrong pressure sender for your gauge it will read low or high depending on the mismatch.

The 73-91 oil warning lamp switch conducts to ground and then switches off at 5-8PSI.  If you hook the warning lamp switch to an oil pressure gauge it will read 0 and nail the oil pressure gauge as soon as she builds oil pressure.

The 73-91 temp warning lamp switch is off till the engine gets above @240°F... then it conducts to ground.  If you hook this to the temp gauge the needle will sit at 0 unless you overheat which will nail the gauge at HOT!!!.

The gauge senders you have to watch out for are the temp senders.  There are at least 4 different gauge senders and matching gauges between 73 & 87.  If you have a 1978 temp gauge you'll need a 1978 temp sender etc...  The old nail head senders are obsolete and there isn't a perfect alternative... just good enough new or working used.

[Rattler12]

Thank you gents .....this explains a lot that's happening. One more question. Does the tan and green wire into the cluster connector go directly to each sender ? If so I want to use them with some gauges I got with senders and cut them before the plug in and piggy back into the gauges instead of running new wiring thru the firewall.

[Irish_Alley]

Want to say yes. But it would be best to test it with a ohms tester