Temperature Switch OMC p/n 0386686 Test

[Terrapin]

I purchased the above "new old stock" temperature switch which came in the original OMC Bombardier box complete with brown instruction tag p/n 319993. Unlike my original sensor, this sensor has the additional ring terminal that gets connected to the engine block.

Prior to installation, I am testing this switch for continuity using my Klein Tools CL800 multimeter set to the audible Ohm setting. With a probe connected to each lead, I am not getting continuity or an audible continuity sound when the water temperature reaches the service manual specified 211 +/- 6 degree temperature or boiling point. In addition, I would have thought I would have continuity from the face of the sensor to the ground ring terminal, but I do not.

Is my "new old stock temperature sensor bad, or am I missing something in my test procedure?

 

[saltchuckmatt]

What engine and what are the two colored wires coming out of the sensor?

 

[Terrapin]

Sorry, this is a 1986 Johnson 150 HP crossflow V6, model number J150TXCDC.
My original temperature sensor only had one tan wire with a knife connector and there was not a separate ground wire.
The "new old stock" p/n 0386686 has a tan wire with a knife connector and a black wire with a ring tongue terminal on it that is supposed to go to engine block ground (a cover plate screw).

 

[saltchuckmatt]

I purchased the above "new old stock" temperature switch which came in the original OMC Bombardier box complete with brown instruction tag p/n 319993. Unlike my original sensor, this sensor has the additional ring terminal that gets connected to the engine block.

Prior to installation, I am testing this switch for continuity using my Klein Tools CL800 multimeter set to the audible Ohm setting. With a probe connected to each lead, I am not getting continuity or an audible continuity sound when the water temperature reaches the service manual specified 211 +/- 6 degree temperature or boiling point. In addition, I would have thought I would have continuity from the face of the sensor to the ground ring terminal, but I do not.

Is my "new old stock temperature sensor bad, or am I missing something in my test procedure?

Yes, not my specialty...typically it's just a ground switch. Not sure on yours....mid wire patch through? I don't get the point. One thing though, you can't get continuity from ground wire to cold sensor. Sensor needs to be hot to complete connection. Make it hot and plug in the tan wire, should blare.

 

[Terrapin]

Understood, I have been taking the temperature sensor surface to 212-degree F using boiling water, but the switch does not close to get continuity and audible confirmation.
With past single tan wire temp sensor switches, I checked continuity and confirmed functionality connecting between the tan wire and temperature sensor surface for continuity at 212 degree F.
Any other thoughts regarding proper test methodology?

 

[racerone]

Send it back to the vendor and get a good one.

 

[cwella]

I purchased the above "new old stock" temperature switch which came in the original OMC Bombardier box complete with brown instruction tag p/n 319993. Unlike my original sensor, this sensor has the additional ring terminal that gets connected to the engine block.

Prior to installation, I am testing this switch for continuity using my Klein Tools CL800 multimeter set to the audible Ohm setting. With a probe connected to each lead, I am not getting continuity or an audible continuity sound when the water temperature reaches the service manual specified 211 +/- 6 degree temperature or boiling point. In addition, I would have thought I would have continuity from the face of the sensor to the ground ring terminal, but I do not.

Is my "new old stock temperature sensor bad, or am I missing something in my test procedure?

You may not be testing it the way the switch operates. The OMC temperature switch is a normally open switch that closes to ground only when it reaches its trip temperature.

The correct test is:

1. Put one meter lead on the switch terminal.
2. Put the other lead on the ground ring terminal/body.
3. Heat the switch in water and monitor temperature.
4. It should show continuity only when it reaches about 211°F ±6°F.

You will not normally get continuity from the sensor face to the ground ring because the threaded body may be insulated from the switch contact depending on the design.

If it still does not close at boiling temperature, it is likely a bad NOS switch. Age can affect these even if they have never been installed. Also confirm your meter is actually reading continuity by touching the probes together first.

 

[Terrapin]

cwella, thanks for your reply defining the correct test procedure. Your procedure matches my test procedure and the procedure defined in my OMC service manual. I also confirmed wire continuity from each terminal to the solder terminal point near the Bakelite housing prior to the test.
The seller was kind enough to send me a second NOS temperature sensor and to my disappointment it too failed the continuity test.

 

[racerone]

Install and test run.

 

[Terrapin]

Install and test run.

racerone, possibly you missed that I followed your advice and got a second one from the seller, but it too failed the test.
Respectfully, I don't understand why I would install a temp sensor switch that doesn't close when subjected to 212-degree Fahrenheit. It might feel good to have it in there, but I have zero confidence it will warn me of an overheat condition.
I will add that the alarm system on the motor works. If I take the tan engine wire (that goes to this temperature sensor) to engine ground the alarm sounds.

 

[saltchuckmatt]

racerone, possibly you missed that I followed your advice and got a second one from the seller, but it too failed the test.
Respectfully, I don't understand why I would install a temp sensor switch that doesn't close when subjected to 212-degree Fahrenheit. It might feel good to have it in there, but I have zero confidence it will warn me of an overheat condition.
I will add that the alarm system on the motor works. If I take the tan engine wire (that goes to this temperature sensor) to engine ground the alarm sounds.

Right, that verifies the horn works nothing else.

I think he's finding it hard to believe you have two failed ones as do I.

Buy a inexpensive IR gun and take it on the lake with a partner. While they drive, take readings from where the head meets the block.

Something seems a miss.

 

[jimmbo]

I am not getting continuity or an audible continuity sound when the water temperature reaches the service manual specified 211 +/- 6 degree temperature or boiling point. In addition, I would have thought I would have continuity from the face of the sensor to the ground ring terminal, but I do not.

Water, as we all know boils at 212F. So with a +2 to +6 degree Variance, there would be No Way the switch will ever close when in boiling Water. The Boiling Point of Water also Lowers, the higher above Sea Level you are.
I suggest you try a Water - Ethylene Glycol mix to get the Boiling Point a bit higher
Just be aware, Ethylene Glycol is Flammable

 

[Terrapin]

Right, that verifies the horn works nothing else.

I think he's finding it hard to believe you have two failed ones as do I.

Buy a inexpensive IR gun and take it on the lake with a partner. While they drive, take readings from where the head meets the block.

Something seems a miss.

The goal here is to replace a faulty temperature sensor that was disconnected since it failed in a closed switch position immediately upon spring cold start up. I have a Fluke IR gun and I verified both my heads are running at appropriate temperatures whether at idle or blasting down the lake. I have well maintained thermostats and bypass valves. No additional testing on the lake is required. I am simply trying to purchase a replacement and verify functionality prior to installing it in the cylinder head. To date, two New Old Stock temp sensors have not closed when subjected to boiling 212 degree water.

 

[Terrapin]

Water, as we all know boils at 212F. So with a +2 to +6 degree Variance, there would be No Way the switch will ever close when in boiling Water. The Boiling Point of Water also Lowers, the higher above Sea Level you are.
I suggest you try a Water - Ethylene Glycol mix to get the Boiling Point a bit higher
Just be aware, Ethylene Glycol is Flammable

Jimmbo, I will retest both switches in cooking oil to ensure I cover the entire range specified for the temp switch closing temperature which is 211 +/-6 degree F per the OEM Service Manual. I'll look for switch closure/continuity somewhere between 205 degree F to 217 degree F (and even higher to be sure).
Thanks for your help.