dash gauge temp sensor

[coopab]

I've been having erratic readings on dash gauge. I pulled the connector and grounded the single wire. When I turned the key to "On" the gauge pegged on H. Decided to replace the sensor.

Why does this sensor have a two prong connection, although only one wire is being used? The old sensor had the same two connectors with only one in use.

To remove the sensor I removed and replaced the thermostat at the same time as replacing the sensor.

After all this the dash gauge isn't moving at all. After running the motor for a few minutes, my ELM327 bluetooth OBD II device connected, Torque Pro realtime temp I was at 190.4 F. No movement at all on the dash gauge.

Is it possible that the new gauge is not connected? (i.e. the single wire feeding the incorrect terminal of the two that are in the sensor)

Ran out of daylight, so I'll be back on this tomorrow.

coopa

 

[RonD]

On all fuel injected engines there are two engine temp reading devices.
A two wire SENSOR and a one wire SENDER.

The sensor is only used by the computer, computer monitors coolant temp to set "choke mode" when engine is cold, i.e. high idle, advanced spark timing and rich fuel mix. This sensor is what you are reading with OBD II reader.
This sensor doesn't use the engine as a ground, that is why it has/needs two wires.

The sender is only used by the dash board gauge, it uses the engine as a ground so only needs the one wire, and this is why if you ground that one wire the needle will go to HOT.

If you picked up a "sensor"(two connectors) to replace the sender(one connector) then it will not work since it has no ground.

Also do not use "sealing tape" on a sender, threads at the bottom must be bare to get a good ground.

 

[coopab]

temp sender connector with two slots

On all fuel injected engines there are two engine temp reading devices.
A two wire SENSOR and a one wire SENDER.

SOLVED: Thanks RonD for clarifying the two items. I just installed the SENDER and made a test run raising the temp into the 190's F while watching the now functioning C---------H gauge rise into the mid range where the thermometer icon resides.

I'm still a little baffled as to why the sender has two terminals even though only one is used in this setup.

The sensor is only used by the computer, computer monitors coolant temp to set "choke mode" when engine is cold, i.e. high idle, advanced spark timing and rich fuel mix. This sensor is what you are reading with OBD II reader.
This sensor doesn't use the engine as a ground, that is why it has/needs two wires.

The sender is only used by the dash board gauge, it uses the engine as a ground so only needs the one wire, and this is why if you ground that one wire the needle will go to HOT.

All of the above I had picked up on after scanning dozens of posts on the subject. Only new point of distinction is the sensor vs. sender. However, the old unit that was giving me erratic readings had two prongs and a two prong electrical connector. The connector, however, only uses one of the two slots.

If you picked up a "sensor"(two connectors) to replace the sender(one connector) then it will not work since it has no ground.

I tried to put up pictures of both sender and sensor but couldn't get the links to work. In any case, since my connector has a double connector do I need to get a replacement for the electrical connector as well as a SENDER with only one terminal?

http://i1198.photobucket.com/albums/aa442/krustybaguette/techsupport/1_WIRE.jpg

Also do not use "sealing tape" on a sender, threads at the bottom must be bare to get a good ground.

I thought I'd solved the problem while lying in bed and I realized that teflon taping the threads wasn't such a good idea. However, I've since removed the tape but no change in the behavior.

 

[RonD]

Company's often use the same connectors for 1 and 2 wire units since it saves money.

Yes, you need a 1 wire sender for the temp gauge.
2 wire sensor for the computer.

But I thought you said gauge was working?

 

[coopab]

boondoggle resolved!

Company's often use the same connectors for 1 and 2 wire units since it saves money.

Yes, you need a 1 wire sender for the temp gauge.
2 wire sensor for the computer.

But I thought you said gauge was working?

It was, but I didn't trust the readings which were erratic. So I got a new sensor, the wrong item (the two wire sensor) which fit in the location where the sender had been.
After one of your post clarified it for me I went back to the store and I got the correct item. During all this I was also using my ELM327 OBDII unit with the Torque Pro program on my smartphone. Realtime monitoring of the actual coolant temperature let me see that the new sender/gauge was working well.