I have a 90 Honda Accord LX, and I'm having issues with my temperature hand on my gauge cluster. I recently paid a so called mechanic $450 to fix that along with a few other problems, and it still doesn't work. Can anyone please tell me exactly what's going on with my car, so I won't continue wasting money with unnecessary troubleshooting...

 

How is the temperature gauge not working properly?

• Does it not work at all?
• Does it work sometimes?
• Does it shoot straight up to HOT?
• Or something else?

 

It's not working at all, and i'm not sure if it's a sensor, or worn out gauge cluster.

 

This is how the temperature gauge works:

The engine coolant temperature gauge has two intersecting coils wound around a permanent magnet rotor. Voltage applied to the coils, through fuse 1 (in the under-dash fuse/relay box), generates a magnetic field. The magnetic field, controlled by the coolant temperature sending unit, causes the rotor to rotate and the gauge needle to move. As the resistance in the sending unit varies, current through the gauge coils changes, moving the gauge needle toward the coil with the strongest magnetic field.

The coolant temperature sending unit’s resistance varies from about 142 ohms at low engine coolant temperature to 13 ohms at high temperature.

Basically the problem you describe can be due to:

• Temperature gauge sending unit.
• The wire that goes from the sending unit to the gauge
• The gauge may be faulty.

Kind of sounds like a faulty gauge though.

1. Unplug the gauge sending unit (it only has one wire (red)), touch the end of that wire to part of the metal engine block (ground). (You may have to use a small piece of wire to connect it to a ground source. Turn the ignition to ON, the gauge should shoot straight up to H (Hot). Once it moves up to H, immediately turn the ignition off, otherwise, you’ll damage the gauge if it was working properly. If the gauge needle moved to H, then the gauge sending unit may be faulty. If it didn’t move at all, there may be an open (break, etc.) in the wire or the gauge is faulty.
2. If the gauge needle moved in step #1, you can do a resistance test of the sending unit if you have a multimeter or ohmmeter. With the sending unit red wire unplugged, 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 , it should be about 142 ohms. If the engine is at operating temperature, it should be about 32-49 ohms. (13 ohms is if the car was overheating.) Check resistance when cold and when the car is warmed up to operating temperature.
3. If sending unit resistance is within ranges and gauge still doesn’t move when it is plugged back in, then the wiring may have an open.

If the gauge unit is faulty, the gauge unit is separately replaceable from the rest of the instrument panel. You can probably pick one up for not too much at a salvage yard or ebay.

 

Ok, I will check into that. I really hope this works, because I've spent too much money for a half done job.

 

Do the tests first, do not just replace parts without doing the tests. You may want to post your test results; so, that you can get opinions on whether your conclusions are correct.

 

I just replaced the temperature sending unit, and the temperature gauge still doesn't work. I don't know what the problem is, and I don't wanna spend anymore money guessing. Can someone please tell me what to do from here???

 

Instructions were already posted above.