Hi, you all were a great help with my previous transmission problem, I'm hoping you can help me with my latest adventure.

Car: 1992 LX, auto, 158,200 miles. Temperature has never, I mean never, gone above the half way point on the dash gauge.

Problem: Temperature gauge shows the engine getting considerably warmer than ever before.

Symptoms: When car is idles too long, or is driven under stress (uphills with A/C on), the temperature gauge climbs to the top of it's range.

What I checked so far:
Coolant level and mix are good.
Secondary (in front of radiator) cooling fan does not turn on.
Primary (behind radiator) cooling fan does run.
Cooling fan fuse in under-the-hood fuse block has been pulled and checks good with an ohm meter.
Coolant is circulating, once thermostat opens (viewed with radiator cap off).

My suspicions:
1) Maybe a bad secondary fan. Haven't checked it yet.
2) Maybe a bad thermoswitch for the secondary fan.

My questions:
1) Does anyone know exactly what triggers the secondary fan to come on. It is not moving when the temperature climbs or when the A/C is on. I think it used to run immediately when the A/C was turned on.
2) Where is the thermoswitch located on this engine for the radiator fans?
3) What should the resistance read for the thermoswitch read when the engine is hot?
4) Anyone have the shop manual....if so, could you check the troubleshooting and give me any other ideas?

Thanks, guys.

 

its probably the sensor that plugs into thye radiator (on the top of the radiator on the drivers side) try that and see if it works.

 

TXprotege,

Any idea what it should read on an ohm meter, when the engine's hot? Or is the only test remove and replace?

 

I think if it is the water thermosensor, then the fan should come on when you turn the A/C on even if the thermosensor is bad. If it isn't coming on when you turn the A/C on, I would bet it is the fan itself, not the thermosensor.

 

I'm going to hot wire the fan directly to the battery tonight, to see if it works. I'll post my results tomorrow....once I find some wire to make the connection. The connector on the fan is deep enough that my fat hands can't get a grip on it. I might need to remove the center grille to get to it.

It's definitely the next step in the diagnostic process.

 

Is there a fan in FRONT of the radiator? I had never noticed one there before on my '92 and my Daughter's '91. Both of my cars are suffering from cooling problems at the moment. Everything was great until it started getting warmer out. Can anyone tell me when the fan up front is suppose to run and how long should I wait for it to kick on?

 

On my '92 LX, there are two cooling fans. While facing the car with hood up, you will see the primary fan on your right (driver's side) just behind the radiator.

Then look down between the radiator and the front grille. You will see the secondary fan on the left side, in front of the radiator and A/C condenser (assuming you have one).

Followup on my problem...

I played around with the car the other night and was unable to get the seconadary fan to run because of the configuration of the plug...I just couldn't get both wires in the plug simultaneously to see if it would run firectly off the battery.

But I did discover a new and, I think, important clue. When the car is running the gauge suddenly starts to climb. It's not a gradual process. It also will drop suddenly downward and bounce around a little. But if you shut the engine off, and then but the key into the accessory position (to activate the gauges), the gauge only climbs to it's usual lower middle position.

Right now, I'm thinking the car is not running hot, but that either the temperature sending unit is going bad or the dash gauge is going bad.

My plan is to keep this car until the autumn, so I think I'm just going to watch this for a while and see what happens. I'm keeping my fingers crossed! I don't really want to spend any money on this now. This car will not be a trade in or for sale, but probably donated to the Kidney Foundation for a tax break.

 

Final update on this problem...

I finally determined that the temperature gauge was not giving an accurate reading, and that I would ignore for the remaining (limited) life of the car.

Unfortunately, fate stepped in and altered my plan. A few days ago, the starter completely gave up the ghost. Turn the key and only get a quiet click. I assumed it was the battery and replaced it (the old one was 6 years old). Next morning, the car marooned my wife at the supermarket (it was the first time in ten years and 158,300 miles that it marooned us).

AAA towed to our local garage where the starter issue was diagnosed. A salvage unit was dropped in and we were roadworthy again.

I went out to get gas that evening and, lo and behold, the gauge is functioning perfectly. While it's beyond my ability to suss it out, there was a connection between the starter replacement and the gauge issue. In hindsight, we realize that the starter was giving warning signs for about as long as the gauge was acting up.

That's it. Thanks for all of your help and suggestions.