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Temp reading in TEST mode - what scale?

7K views 6 replies 5 participants last post by  mateofelix508 
#1 ·
Folks,
I'm wondering about the temp display when the instruments are in TEST mode.

I have a 2007 TDCi. I started it in TEST mode, clicked through to temperature, and saw "89 C" (it had been run a few hours before).
Started the motor, and it slowly increased. Ran it at ~2,500rpm for some minutes.

The radiator hoses only got hot when it reached "125 C". It then dipped to around "120 C", and slowly rose again. I presume the thermostat just opened.

I kept going, and at "137 C", the fan came on.
The dash guage never rose above half way.

Q1. Is this *really* in Centigrade?
Or is it just some arbitrary scale?
It seems pretty darn high to me.
Also, the guage's low mark is marked "60 degrees C", and high mark is "120 degrees C". It doesn't match.

Q2. What values do you folk normally see?

So why am I doing this in the first place?
I'm debugging a cooling problem in a Lotus 7 type car with a 2.0l Duratec from a 2006 Focus. Ok, different motor, but electronics mostly the same, and the diesel is my daily driver. In the 7, sitting still it reached "122 C" with seemingly no thermostat open, and no fan running, before I gave up. The fan works when the ECT lead is pulled. After that, I played with the TDCi as above.

Hope you can help, thanks - Gavin.
 
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#2 ·
I'll have a crack at answering my own question.

I now realise that the Duratec's 'CHT' sender is actually measuring the tem of the cylinder head itself, not the coolant.

Q. Does this mean it's reasonable to have higher temperatures reported than you'd normally expect in coolant ?

Gavin.
 
#3 ·
Yeah it's in C, and that's ridiculously high. Do you have the water flow going in the right direction? The lower hose is the one with the thermostat near the water pump, and that's the water intake side. Water out side is on the back end of the head. If it was in F, then it would be cold, boiling is 212F.

Once you figure your problem out, you should change your hoses. You definitely have a cooling problem. Yes, the Focus CHT is a cylinder head temperature- however, it should still read temps right around the thermostat temp which is 90C. In your application you might even want a colder thermostat.

I suggest removing the thermostat for now, see if it runs that hot without a thermostat if you can't find any other cooling issues. That way you can check to see if the radiator is flowing properly.
 
#4 ·
Yeah it's in C, and that's ridiculously high ...
Sorry whynot, but it's is NOT in Celcius, even though it says "137 C" or similar.

I plugged in a reader to the OBD port. Engine cold.
OBD says 10degC. About right for a cool morning here.
Dash says "50 C".
Start engine.
Both OBD and dash rise together, exactly 40 apart.

Eventually OBD says 90degC, dash says "130 C". Bottom hose gets warm (thermostat's just opened), and fan comes on.

On the road, it hovers around "137 C".

On the plus side, I haven't stuffed my motor, & I now have a spare thermostat!
On the down side, I spent about 2 weeks fluffing around trying to "fix" a problem that wasn't there.

Cheers - Gavin.
 
#5 ·
I don't know why but apparently some of the values the 'test mode' displays are wrong as you have found out.

I ran into the same problem when monitoring my battery voltage. Test mode always indicated 5 volts higher than actual battery voltage when I measured it with a meter at the battery.

You may have saved yourself a little time if you had one of those infrared non-contact digital thermometers. About $10 U.S. They work well.



http://www.focusfanatics.com/forum/showthread.php?t=239410&highlight=infrared+thermometer&page=4
 
#6 ·
89*C = 192*F. If your stat is a 195* not open yet.

125*C = 257*F...She's hot!

137*C = 279*F....She's overheating I would assume.

110*C the low fan should have kicked on. Check replay or low fan and see why it didn't come on. Your probably hearing the high fan come on, at the higher temps.
 
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