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Temperature Gage

G

green1999csvt

New CEG'er
Joined
Nov 15, 2005
Messages
10
Location
St Louis MO
Had an issue where temperature gage was reading low, would occasionally come up a tiny bit, then drop back down to low. I replaced the thermostat (the old one fell out in 3 or 4 pieces) and put it all back together. Now the gage needle is well below low and just lays there like the power is off. Yes I plugged it back in to the temp sensor!

My question is how do you check this out? Is temp sensor a variable resistance device I can read with a multimeter? How can I give a dummy signal to the gage to get it to go full scale? Will 12 volts give it a signal or kill it?

Thanks
 
Kinda sounds like a cluster deal. If you see it go up and then back down again, try cleaning out your heater core. Had a car do that to me and thought it was the gauge and turned out to be a gunked up heater core.

Best of luck.
 
99RedCSVT said:
Kinda sounds like a cluster deal. If you see it go up and then back down again, try cleaning out your heater core. Had a car do that to me and thought it was the gauge and turned out to be a gunked up heater core.

Best of luck.
Click to expand...

I have read here and elsewhere that a plugged heater core can cause very low and/or erratic readings on the temp gauge.

Can someone explain to me how on the zetec that can happen??

The water flows from the WP thru the head and block. Then it has 4 routes it could take:

1) thru thermostat, then radiator, to lower hose, to WP
2) thru heater core back to lower hose, to wp
3) thru bypase hose to lower hose, to wp
4) thru the tiny "burp" hose back to the reservoir, to lower hose, to wp

I can't figure out why a plugged heater core should affect the temperature gauge behavior. Seems to me the bypass hose (route 3) would make up any difference.

Can someone enlighten me?

Thanks,
John

P.S. I have a 96 contour 2.0 which is seeing such erratic temperature indications, I've ruled out the thermostat and water pump.
 
Heater works fine. Gage needle is lying below normal power-on zero, if you know what I mean. What is the technology of the sensor? It is a two wire connection, is it resistor that varies with temp? If so, I can measure that and determine what to look at next,. Seemed to just fail after I pulled wire off and then reconnected after thermosat repalcement.

Thanks
 
Got my answer!

Got my answer!

The engine coolant temperature sensor resistance changes in response to engine coolant temperature. The sensor resistance decreases as the surrounding temperature increases. This provides a reference signal to the PCM, which indicates engine coolant temperature.
 
I just replaced the temperature sender not sensor on my '97 Mondeo. Did the exact same thing - eratic readings or none at all. There are two sensors. The one to the gauge is under the thermostat so replace the stat as well. An easy way to drain the radiator- there is a coolant line on the underside of the motor passenger side close to the wheel. Easy to spot and much easier than draining the radiator. You'll have to put the car on a jackstand to get at it.
 
fever62 said:
Did the exact same thing - eratic readings or none at all.
Click to expand...

I replaced the lower sensor when I replaced my thermostat and it has always read at about "N" of "Normal" regardless of if I had my GL cluster in or upgraded to a Mystique cluster. I figured I had a sensor with a different temp setting than stock, but it's not overheating the engine or anything since it's just for the cluster gauge. Is there a specific sensor to use?
 
I spent more time researching this subject than the time it took me to do the repair. One guy said that he had used 6, yes 6, different senders and got a different reading from each one. It is my understanding that these senders are all over the place as to where they read on the gauge. Most have said that if it isn't overheating and tends to read the same every time it's fine just a little annoying.
 
fever62 said:
I spent more time researching this subject than the time it took me to do the repair. One guy said that he had used 6, yes 6, different senders and got a different reading from each one. It is my understanding that these senders are all over the place as to where they read on the gauge. Most have said that if it isn't overheating and tends to read the same every time it's fine just a little annoying.
Click to expand...

I wonder if there is a difference between the Ford OEM and the generic parts store senders or switches (in this case). I have a second one that I was planning to put in if I needed to replace that rubber basket-to-block o-ring at the end of the thermostat housing.

The Ford OEM p/n for the Zetec engine is F5RZ 10884A.
 
I had a problem with my CSVT when one morning I started it and the temperature gauge slowly went completly over to the max high temp position. I knew it had to be only an instrumentation problem, so I bought a new sending unit from NAPA and installed it. Well, after completing repairs I fired her up and drove it around to get the engine up to normal operating temp and the temp gauge didn't stop until it reached the "L" in "NORMAL" now I was somewhat alarmed but I was also not completly trusting the new sending unit, it wound up being a really hot day so after my drive home from work in plenty of stop and go traffic I let it sit and run for about 20 minutes and the temp cycled slightly when the fans would come on and off but remained up at the "L". So I decided to replace the sending unit with one from Ford and when I did the temp gauge began reading perfectly normal right in the middle of the "RM" in NORMAL" so I talked with NAPA and they said that the unit I bought was also standard replacement part for like 22 other vehicles! and not all of them were Fords meaning it was only a "ball-park" range not an exact replacement. Problem is with parts which operate off of resistance it don't take much to push you "out-of-range" when using non-OEM close-enough parts. The aftermarket manufacturers do this to cut down on the number of parts they need to produce thereby increasing their profit but unless your particular installation happens to fall in the middle of the range for that aftermarket sending unit you are going to have a false reading, and if it falls on the low side you are going to have a real problem when it does overheat it will actually be hotter than the gauge indicates. Lesson here is to buy from the OEM for this part, it's only a few bucks more but well worth it.
 
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