Why does my 4.3 GL Volvo/GM Have 2 water temp sensors?

[Alphams]

I'm confused. There are 2 water temp sensors on my 4.3. One is mounted on the intake manifold and one on the thermostat housing. Which one is the real temp sensor? I noticed that the one mounted on the thermo housing does not have 5vdc going to it while the one on the manifold does have 5vdc.

 

[Fun Times]

Hi, welcome to iboats!!

One would be for the temp gauge while the other is for the temp warning horn.

Do you have your full engine model number handy? http://www.volvopentastore.com/mall/...enta/help.html

 

[BRICH1260]

I think the intake one is the guage, the thermo housing is for the alarm.

 

[spoilsofwar]

I think the intake one is the guage, the thermo housing is for the alarm.

Correct. The one in the manifold is a sender, while the one in the thermostat housing is a sensor. Found this out myself recently.

 

[Alphams]

Thanks for the replies. The wire going to the sensor on the thermo housing has no voltage on it. Is that normal?

 

[Fun Times]

Thanks for the replies. The wire going to the sensor on the thermo housing has no voltage on it. Is that normal?

No the warning horn wire/sensor shouldn't have voltage readings.

The warning horn itself will be connected to 12v+ power on one of it's wires while the other horn wire that you have there at the sensor is basically waiting to see/go to ground in order to sound the warning horn as the sensor switch resistance changes state (gets to hot).

The way to identify and know if that system is working correctly is to use a jumper wire and touch the sensor wire terminal connector to engine or battery ground while either the key is on or have the engine running if needed. The horn should sound/beep...Or should that wire be for the temp gauge, the gauge would go to max temp when grounded while the key is in the on position.

 

[Alphams]

Got it. Thanks for the help.