The gauge is actually controlled independently by the Coolant Temperature Sending Unit. I looks similar to the Engine Coolant Temperate Sensor except where it plugs in. The Coolant Temperature Sending Unit has a single tab, and the Coolant Temperature Sensor has a two prong plastic plug.

Your car can still work if the Engine Coolant Temperate Sensor fails, because the ECM has a fail safe system; it just theorizes what the temperature should be. I imagine in this mode it kicks your fans in a lot more often like what you described, but the field service manual doesn't mention it.

You would think if this is going on then the car would have thrown an engine code.

Well it's a cheap part ($10 at Rockauto.com), and they often go bad, so I would just replace it myself.

You can test it with a multimeter, but you really need to uninstall it and boil some water to a specific temperature(you'll need a thermometer) to test it. I wouldn't drop the whole thing in the water, just the sensing part.

Check resistance as shown:
20 degrees C (68 degrees F) = 2.3 - 2.7 kΩ
90 C (194 F) = .27 - .26 kΩ
110C (230 F) = .14 - .15 kΩ

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I just looked at the FSM page EF & EC - 215 and it says there are 3 things that decide when the fans come on:

Vehicle speed sensor - if you're going fast it doesn't need the fans to kick in nearly as much.

Engine coolant temperature sensor

and whether the AC button is on or off - if the ac is on, the fans will kick in way more often.

 

b13er,

Thank you for the information! I will order the sending unit. Do you think the sensor needs to be replaced as well? Also where is the location of the sending unit? It looks like its located on the thermostat housing where the lower radiator hose is attached to engine. Again thank you for the help!!

Charles

 

You want a Engine Coolant Temperate Sensor (plastic 2 prong connector) like this: http://www.rockauto.com/catalog/moreinfo.php?pk=951105&cc=1212949
The Sending unit(with one tab) just makes the gauge work, it doesn't affect the car's performance at all. As long as the gauge works and looks like it's doing what it's supposed to be doing, replacing the sending unit would just be a waist of money.

The Engine Coolant Temperate Sensor is located on top of the engine, under the passenger side of the intake manifold. I tested mine recently and it was almost impossible to get both of leads from the multimeter to touch both of the leads on the temperature sensor, but I did it.

I'm not sure how hard it's going to be to remove it since it's under the intake manifold. Just pray you don't have to take the intake manifold off. The Haynes Manual doesn't mention it, and so I doubt you'll have to.

Just for reference, the Sending Unit is on the driver side of the engine, underneath the distributer, and again, replacing it will not affect anything except for the temperature gauge.

 

I would check and make sure you have a Engine Coolant Temperate Sensor before buying one, I'm no expert on 89's, nor do I have the shop manual for one.

Your problem sounds odd, I'm highly suspicious there is no problem. Try this: when the engine is cold, start the car. With the AC off, let it idle and keep watching the engine temperature gauge in your car.

Once it's warmed up to 91 degrees C (196 F) the fans should kick on. At 105 C (221 F) the fans will go in to high speed. 196 degrees F will be very close to the normal operating temperature on the gauge, but you're mostly guessing. Don't get a 3rd degree burn taking off the radiator cap if you plan on using a thermometer to check the engine temp.

When the AC is on the fans kick in much earlier, but the graph in the field service manual doesn't specify exactly when.

 

If it's an 89, I believe you have the GA16i engine. The ECT sensor should be on the right hand side (passenger) of the engine, on the top side.