Hi All,
I just got my '69 Cutlass Supreme a few weeks ago, and I don't have any shop manuals for it yet. I don't really know the history of the car, but the engine is an Olds 350. As you can see in the attached picture, there appears to be two temperature sensors. One on the water pump and one on the intake manifold. The one on the manifold is snapped off. Are these both actually temperature sensors? If so, what is the purpose of each? I hope that this isn't a dumb question. Thanks!

 

'IF' I remember correctly the one on the intake controlled vacuum to the distributor vacuum advance. At certain temps the distributor vacuum advance would have vacuum or no vacuum.

 

Unfortunately, I am on my phone, and the picture seems a bit dark where I think you're looking, but if in correct, you're SI
Ing at the oil pressure sender (on the shelf above the water pump) and the distributor thermal vacuum control (on the manifold).
The latter is an emission control device designed to allow the engine to run on ported vacuum advance at idle, unless it began to overheat, in which case it would switch to full manifold advance.

- Eric

 

Curse you Autocorrect!
I will fix the errors when I get home.

 

I see a temp sensor for an idiot light and a oil pressure sensor for an idiot light

 

The one behind the water pump is your oil pressure sending unit for the OIL light and the one on the intake is the water temp sender for the HOT light.

 

The one that's snapped off is the temperature light sending unit. The one between intake and w/p is the oil pressure light sending unit.

If car had a TVS (that switched distributor vacuum between ported and manifold vacuum depending on coolant temp), it would be on the passenger side of the radiator hose.

Both senders should be easy to find at the auto parts store.

 

It looks to me like the top of the temperature switch broke off and is hanging by the wire. The fitting on the intake manifold next to the thermostat housing is that temperature switch for a car with a warning light. The other switch connected to the flat section of the block behind the water pump is the oil pressure switch also for a warning light. The wire to the temp switch should be green and the oil switch wire should be blue.

The references made to the vacuum switch for controlling vacuum to the distributor will be located on the other side of the intake manifold in a similar location to that of the temperature switch. It just has vacuum hoses going to it and no electrical wires.

Since I assume you want to replace that broken switch, it is the temperature switch and tell the store it is for a car with warning (idiot) lights. Now if you have a gauge for temperature instead of lights, you'll need to tell them that.

when you replace this switch, make sure the cooling system isn't pressurized and the engine has cooled. If the engine is cool, just loosen the radiator cap to relieve the pressure if it is there. Use a little thread sealant or teflon tape on the threads if the new switch doesn't have sealant on it.

 

x2

 

Thanks guys for in info! I'm new to the Olds engine game, as I've traditionally been a Chevy guy (and its been 20 years since that!). If I wanted to add a set of temporary under-dash guages, can I replace the idiot light temp sensor with a gauge type sensor?

 

Yes you can.