Thermostat Gauge Stopped Working

[BuckeyePEV]

I'm a rookie, and somewhat of a youtube handyman, so a couple of questions:

it's a 1994 5.7 Merc Alpha One -

1) to check the sensor ground to see if it's the gauge - where is the sensor? is it the one with red near the tip? (on the right side looking down at it) It looks there are 2 things going into the housing, one each side
2) to replace thermostat - are all 4 tubes going into the housing, or just the 2?

I have a picture below, or attached.

 

[hughespat57]

All four hoses go to a single iron casting that is the thermostat housing.
The two bolts under the lifting eye hold it to the engine block.
There flat steel plate under the lifting eye, under that plate is the thermostat.
The Thermostat is held in place by white plastic sleeve, take everything apart gently and keep track of the positioning.
There is a small notch and tab that align.
You'll need two gaskets you should replace the top and bottom.

There are two sensors, one with a single wire for the gauge.
The other may have one or two wires together its the alarm, works with the oil pressure alarm buzzer.
If you ground the sensor wire the gauge should go full

 

[Pirate Lady]

Pray the thermo housing is good, just cost me $480 for a new one. Corroded.

 

[BuckeyePEV]

Quick question - heading back up to the cottage this week and going to mess around with this.

I think I got this right:

- brass sensor on the starboard side is the temp sending unit to the gauge
- stainless steel sensor on the port side (with red tape) is the warning gauge/alarm ??

I need to ground the BRASS sensor connection to check if the temperature gauge is bad on the dash.....anything needed for the stainless steel connection?

Please confirm - thanks!

 

[Wanderer 290]

For reference, the “sending unit” feeds the guage and the “sensor” feeds the alarm and any computers.
The sending unit will have only one wire and usually has a crude slip on fitting or possibly a ring retained by a nut on the end of the wire. The wire(s) going to a sensor will have a weather proof connector.

 

[BuckeyePEV]

For reference, the “sending unit” feeds the guage and the “sensor” feeds the alarm and any computers.
The sending unit will have only one wire and usually has a crude slip on fitting or possibly a ring retained by a nut on the end of the wire. The wire(s) going to a sensor will have a weather proof connector.

Looks like they both have weather proof connectors ?? - I think the one on the left is the "Sending Unit".

Thanks for your help.