I know this topic has been discussed in different ways in several previous posts, but I'd like to pose the question a little differently...

If I remember correctly, according to the '93 shop manual, the low speed fan should turn on at 212 degrees F, and the high speed fan(*) should turn on at 226 degrees.

I've wondered about the high temps in my '92 SSE */c since I bought it a few years ago. The other day I stopped the car and looked under the hood when the temp gage read 220 (the 1-o'clock tick mark) and neither fan was spinning. Isn't the smaller fan supposed to turn on when the coolant reaches 212 degrees? I turned on the AC and then saw that both fans were spinning. I then turned off the AC and saw that both fans were still spinning. I already knew that both fans are supposed to turn on when the AC is on, and since both fans turn on I know that the smaller fan works ok, but I'm wondering how to test "low" speed fan operation.

I took a peek at the cooling fan diagnostics in the Pontiac shop manual, but the tests specify the use of a Tech1 scan tool, and I don't own one.

Can anyone tell me a simple way to check for "low" and "high" speed coolant fan operation without using a scan tool?

When you turn on the A/C, an override turns on both fans, as you've seen. Otherwise, there'* a temperature sensor that'* supposed to turn the fan on when needed, and it sounds like maybe yours isn't. I don't know offhand where yours would be, but if it can be located, I _think_ you would then ground the wire connected to it and see if the fan turns on. If so, and the gauge shows that the fan _should_ have been on all along, then I'd replace the thermal fan switch.

Only thing is that I can't tell you right now where that fan switch is; maybe someone else can. I also wouldn't want you to go replacing the computer'* engine temperature sensor by mistake, as there may be more than one temperature sensor on the engine, and you only need to fiddle with the one controlling the cooling fan.

I believe many of the stock temperature gages on the Bonnys are off. The best way to get your real engine coolant temperature is to use the diagnostics mode on the climate control.

Do you have a service manual? It will tell you how to read the coolant temperature digitally from the climate control head. It gives it to you in celsius. Just convert the fahrenheit set points for the low and high speed fans to celsius, and then sit and watch the display and fans.

Yes, I have the factory manuals, but a little help would be greatly appreciated.

I once had a need to run the climate control diagnostics when the AC system on my '93 SSEi stopped working correctly, and I was impressed with the firmware that GM had designed into the AC control head...but I wasn't aware that the control head can display the coolant temp...and are you saying that the control head can indicate when the 2 cooling fans are on? That would be a handy thing to know, and I'm sure I'm not the only one here who would be interested in that info.

Thanks.

Just take a peek at your service manual. The procedure is too complicated for me to spell out here, but the engine coolant temperature can be displayed on the control head. No, the fan operation can not.

So, watch the display. When you reach the temperature set point, go out and look at the fans on your car. Or wait until the fans come on and then go and look at the control head for the temperature.

Thanks for the tip.
I'll try it as soon as I can.

Did you do this on yours, and if so, do you remember how far off the temp gage was?

Yes, I remember it read significantly higher than reality. (If the digital temp gauge reads reality).

I believe one of the options you can select is to override or correct the sensor readings -- at least some of them.

But getting back to the main point here, I think the question is which sensor actually turns on the cooling fan, or whether the computer does it. i.e. Is it the old design where you have a separate fan circuit, consisting of just a cooling fan, power supply to the fan, and a thermal switch in the engine block which will ground the fan to turn it on when the engine gets too hot? If so, all he needs is a new thermal switch (since we already know the fan itself works, if he selects the A/C override). I'd go through the manuals myself except they're down in the garage and it'* too late in the evening and I'm supposed to be packing for my trip anyway...

If it'* not the simple old-style circuit, he might still need a new temperature sensor for the ECM (or climate control, whichever one it'* talking to), since if it'* not giving a hot enough reading, not only will the fan not come on when it'* supposed to, but the engine might be keeping itself in warmup mode too long (although you'd think there'd be a Service Engine Soon light or three about that by now).

Come to think of it, the climate control is only interested in engine temperature so that it knows when to turn on the heater fan (i.e. blower) in cold weather. Wouldn't the ECM be in charge of _controlling_ the engine temperature via the fans?

So you mean to tell me I don't need to get one of them fan overide control module.. but simply splice another ground with a switch to get the fans on whenver I want? hee hee.. might look into that instead of shellin out for that..

And for the coolant readout on climate control.. can someone email me the pages ( via scan ) or tell me how.. ( it seems lengthy ) for a 97 and 00 ?? thanx

Drifter,
After looking through my 97 service manual it looks like the "display trick" won't work on the newer cars.
You can't just ground the sensor and/or the relay on the 97, it will turn on the SES light. I found a fix though, the ZZPerformance high low fan switch. http://www.zzperformance.com/zzp/pro...witch_hilo.htm
It is designed for the Grand Prix, but it will work on the Bonneville also. The wiring is basically the same, but the fans will turn off when the key is off instead of continuing to run as stated in their description. Because of this you don't need the timer module . I just installed it on my 97 and I have low speed or high speed fans when I want or I can turn it off and the ECM controls it.