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[Perplexer]

Hello.

I am having problems with the engine temperature in my car so I need some help.

My car:
Opel Omega B, year 1998, 5-speed manual transmission, automatic climate control, 2.0 16V X20XEV engine.

Problem:
The temperature gauge in the dashboard regularly goes to over 100 Celsius and the red temperature
symbol lights up. A few years ago when everything was working correctly, I have tested the cooling
fan activation temperature, and it was at 95C-96C. Unfortunately I didn't check whethere both fans
were spinning then or if just one was spinning. I also don't know if it was spinning at full speed
or half-speed. But I know it turned on at cca. 95C-96C.

So I decided to do this test again today to see what is happeninb. AirConditioning was turned OFF !

I turned on the car in my driveway and left it running. After about 10-15 minutes, the temperature
reached 95C. Then it was slowly rising by 1 Celsius every 1 minute and reached cca 97C-98C. The fan
still didn't turn on. Then the temperature jumped from 98C to max. (100+C-105+C) in only 5-10 seconds and
the red temperature symbol came on. Then after 15 seconds both fans (main cooler fan + AC fan)
started spinning, but I think only at half speed because it didn't look very fast to me. Is that
"stage 2", since both fans are spinning, or is it "stage 1", since they are spinning slow?

They were spinning for maybe 10-15 seconds and then they turned off. But the temperature gauge
in the dashboard was still on 100+C with glowing red symbol. I then turned off the car.

So now the question is ... is the reading in the dashboard wrong (temperature sensor displaying
wrong temperature?) or is there something wrong with the fan switches? The coolant is fresh, level is
good and there are no leaks anywhere.

Since I know that the main fan turned on at 95C in the past, it looks like "stage 1" is not activated
anymore at 95C. Or it is activated, but only later at 100+C. I'm not sure whether it is stage 1 or stage 2
because both fans start to spin, but they seem to spin slow. I'm not sure how it should be.

I used some contact cleaner on the two temperature switches on the front (on the radiator, top one
with 2-pins and bottom one with 3-pins) but it didn't make any difference. I didn't check/touch the
temperature sensors behind the engine because I could not get to them.

How do the two temperature switches in the radiator work exactly? Are they in direct contact with the coolant?
Are they controlled by the coolant temperature or by the temperature sensors behind the engine? If I wanted
to replace the two temperature switches on the radiator, would I need to drain the coolant out first ?

What are the correct "stages" ?

Stage 1: radiator fan half-speed?
Stage 2: radiator fan full-speed + AC fan half/full?

Has anyone investigated this before ? Any tips on what I should try next would be appreciated. Thanks.

Pics for reference:

[danzigfan]

Could it be thermo switch fault? Disconnect thermoswitch and short the wire therminals to see which fan should be activated when temp reaches 96 deg and speed of it.
Thermoswitch is cheap as chips and easy to replace for a start

[Doctor Gollum]

What does live data say?

Gauge, ecu and fan thermoswitches are three different circuits...

Ecu and and fans are linked, but gauge has its own sender

No point condemning the entire fan system for the sake of a five pound gauge sender...

[Perplexer]

I guess you're talking about the sensor for the dash gauge shown as (1) in this picture:



Can it be that this sensor/sender still "works" but is just showing wrong temps? What would be the way to determine if it's working correctly? To compare it with the reading that the sensor for the ECU (pictured as (2)) is sending? I guess I would need a scan tool to read that temperature (which I don't have), right?

So since I don't have a scan tool to compare sensor (1) and (2) temperatures (if they even can be compared like that), what are my options? Start with buying sensor (1) first or one or the switches on the radiator first (in case the one responsible for activating "stage 1" is bad and has a delay) ?

From what I described it seems that the "stage 1" fan cooling does kick in, but way too late ... or maybe it's at the right time but the sensor for the dash is just displaying skwed temps and it's really 96C and not 105+C. Could that be a possibility ?

[Doctor Gollum]

Yes, the last point, and for the reason I mentioned

[Perplexer]

I got the coolant temperature sensor (sender for the dashboard) replaced today and while the readings are a bit smoother than before, the needle does still climb to 100 C and over. At around 110 C both fans (radiator fan + AC condenser fan) start spinning, with what I would call half-speed. I read on-line that this is the fan "stage 1". "Stage 2" should be when the radiator fan spins at max speed and "stage 3" should be when both fans spin at max speed and the AC compressor is shut down. At least that's what I read online at various forums.

If that is accurate then it means that my "stage 1" cooling only activates at 110 C which is way too late. Both fans spin for maybe 20 seconds and then stop, and the temp drops to around 97C, and then climbs again to 110C, and the cycle repeats. This is weird because I would expect "stage 2" to kick in at 110C and I would assume "stage 1" was just "missing".

Now I'm not sure which of the two thermo-switches I need to replace on the radiator, the upper 2-pin one or the lower 3-pin one? Which one is responsible for the proper 95C "stage 1" colling activation ?

Thanks.

[danzigfan]

https://m.ebay.co.uk/itm/Radiator-Cooling-Fan-Temperature-Switch-Febi-Bilstein-17696-Top-German-Quality-/201959868401?_mwBanner=1

I believe it's lower one, with three pins. As far as I remember on my previous 2.0 16v, fans kicked in at around 96C as stage one as you say and never reached over 100C

[Perplexer]

I checked the GM EPC (Electronic Parts Catalogue) and found that the upper 2-pin thermo switch (Part No. 90242277) has an XC marking (which I confirmed by looking at it) and the lower 3-pin (double-thermostat) switch (Part. No. 90376209) has an WM marking on it (I couldn't confirm that by looking but I kinda trust it to be true).

I then Googled the specs for thermo-switches with XC and WM markings and found that the 2-pin "XC" ones have a temperature range of 100C-95C (for example Wahler 6031.100D) and 3-pin ones have two temperature ranges, one from 105C-100C and one from 120C-115C (for example Hella 6ZT 007 835-151). I'm guessing the upper 2-pin one activates "stage 1" at lower temps (100C) and the lower 3-pin one activates stages 2 and 3 at higher temps (115C and 120C).

That would mean that my XC switch turns on the fan in stage 1 at 100C and turns it off at 95C. But, like I mentioned, when I did a test a few years ago when everything was working, I clearly heard the fan come on at 95C or 96C. Not sure how that's possible if it should only come on at 100C with "XC" type switch.

Confused.

[Doctor Gollum]

Has the thermostat ever been changed? Usually they fail open, but could have failed closed/almost closed

[Kevin Wood]

What does the temperature gauge indicate when you are driving? Particularly cruising at moderate speed where the fan won't be needed?

If the indication is normal, I'd say it may be the thermoswitch. If it's still high, then thermostat / water pump / gauge still not reading correctly.

Might be worth pressing the instrument panel firmly home in case there's an intermittent connection back there. Also check the engine to battery and chassis earth strap(s).

[casared]

I had similar problem on my 2.2 a few weeks back. After numerous tests found Thermostat stuck closed. Renewed thermostat problem cured   

[Perplexer]

Thermostat was replaced 3,5 years ago which was 4000 km ago (I don't drive the car a lot).

Tehmerature when driving .... that's hard to say. The temperature light DID come ON on two occasions while I was city driving (110C). However yesterday it did not. It hovered between 97 and 100 (perhaps due to a bit colder weather now). But when I parked the car, I left it running to see what would happen. And sure enough, after a minute or two the temperature on the dashboard reached 110C and the temperature symbol came on. At about that time the two fans started spinning (at half-speed to my eyes/ears) and the temperature went down to perhaps 98C. The fans stopped after only 20-30 seconds and then the temperature rose to 110C, and the cycle repeated.

It's all very confusing.

[Chazza12]

termol fan resistors are under the battery housing white or black with wires coming out, fixed mine a few months back as was doing the same thing. the connections are swered on and its a bad area for when water gets splashed in there making the connections bad. also the case can crack from the heat and let water and damp inside, just cleaned mine and filed the cracks with heat proof glue, think first fan setting comes on at around 93c next is full speed at 95-97c. the resister is for first speed that is low. second is direct power. 

[cam.in.head]

What does the temperature gauge indicate when you are driving? Particularly cruising at moderate speed where the fan won't be needed?

If the indication is normal, I'd say it may be the thermoswitch. If it's still high, then thermostat / water pump / gauge still not reading correctly.

Might be worth pressing the instrument panel firmly home in case there's an intermittent connection back there. Also check the engine to battery and chassis earth strap(s).

Very good point and worth noting. If you are getting a resonable flow of air through the radiator with normal a or b road driving (not motorway)and not sitting in traffic then are you getting normal temp guage readings ? .the fans realy only come into play when the airflow is not enough to cool the engine.ie slow speed/stuck in traffic or stationary.it would suggest an issue with the fans. If you are not getting normal readings or if the engine goes cool after a motorway run it suggests a problem with the thermostat ,either being stuck open allowing too much cooling or stuck partially open only not allowing enough.