Problem with temp gauge
 

hello and thank you to all for reading this post. I have a 1994 Honda Accord with the 2.2 L standard engine with an automatic transmission.

recently I did a lot of work to it and which one of them was that I had to replace the radiator.

after replacing the radiator and refilling the coolant and bleeding the air out of it etc.
The temperature gage went funny on me.
what happens now is that I turn the key to the on position and the gauge is already in the middle even before the car starts and while it is cold.
so when the car warms up the gauge reads up in the red zone maximum.
hi don't know why this would suddenly happen after changing the radiator and less I accidentally bumped something while working on the car.
or if the gauge coincidentally went bad.
does anybody out there know what would cause a temp gauge to be reading in the middle before the engineering starts in while the car is cold?

any help would be greatly appreciated thank you

Try unplugging the sender (side of head, 1-wire connection). The gauge should remain at the very bottom (cold). If not, then you have a connection to ground somewhere along that wire. If it was a complete short-to-ground, the gauge would go up all the way to HOT.

While testing, if you touch that wire to ground, the gauge will go up to HOT. Don't let it get all the way up, because that could damage the gauge.

Hi Jim

I did like you said and disconnected it and you are right, it stayed at the bottom (cold)
hooked it back up and turned it on and the gauge went back to the middle again .
Is there something I should be looking for ?
Could the sending unit be defective ?

Do you have a multimeter or ohmmeter, so that you can do a resistance test of the sending unit?

Unplug that one Yel/Grn wire from the sending unit. Measure the resistance of the sending unit between the positive terminal of the sending unit (tip of the sending unit) and engine ground. When it is cold should be about 137 ohms. If the engine is at operating temperature, it should be about 30-46 ohms.

If the sending unit's resistance is about 137 ohms when it cold, then the sending unit may be okay. If the resistance was 137 ohms when cold, your gauge needle shouldn't have moved straight to the middle when you turn on the car.

I have a multimeter but I have never used it and I am quite electronically challenged .
There are so many settings on that thing.
I am wondering if I should just pull one of those senders from the wrecker yard or buy a new one (?)

Set the meter to measure resistance (ohms). Touch the meter leads together, it should read close to zero (just as a check).

Now touch one lead to the metal of the cylinder head, and the other to the terminal on the tip of the temperature-sender. What does the meter say?

Some meters display kilo-ohms, so look at the instructions for the meter. 137 ohms is the same as 0.137 k-ohms.

Sender from a wrecker yard might be bad too? So it would be good if you know how to measure it before you take it from the wrecker.

if I remember correctly the senders are >20bux... If that is what it is.

I suggest testing like Jim suggested to determine what the specific issue is.

either you've got a wire pinched/crimped/rubbed, or the sending unit, or the gauge itself.

If it was a pinched wire, then the gauge would have gone up even when the wire was disconnected from the sender. That's why I asked him to try disconnecting...

I hooked up the voltmeter and with the setting on 200k with engine cold and key in thieving position the reading was 00.4

Does this mean it is good or bad ?

Attachment 12013

* in the off position ( not thieving !)