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Temp. gauge not working

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Old Aug 27, 2004 | 09:35 AM
  #1  
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mkbonnes
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Thumbs down Temp. gauge not working

I have a 1990 F150 4x4 w/351 V8. The temperature gauge reads cold (moves to far left when truck starts). I checked the coolent system and it's working properly. I replaced the coolent sensor, and checked the sensor curcuit but still have no gauge reading. It looks like there is 4.6 volts going to the sensor. (my guess is the voltage passes through the sensors resistor and the changed voltage signel then connects to the gauge and ECC-IV control system.) I did download codes and I got the code that indicates cold operating temp.
My question is,
What is the correct voltage at the sensor (I read 4.6V)?
Are there other parts to the coolent sensor system I should be checking?
If the gauge is bad would that affect the signel to the ECC-IV computer?
Any help regarding this manner would be graetly appreciated.
 
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Old Aug 29, 2004 | 10:18 AM
  #2  
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I too have the same exact problem on my 88 F 250 7.5. I was told this is common and to replace the gauge. I haven't yet because I'm not convinced thats it. How would you test the gauge? Any help would be great.
 
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Old Aug 29, 2004 | 11:43 AM
  #3  
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w6pea
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Temp gauge not working

I had the same problem with my 95 F-250 7.5L I replaced the sending unit under the hood and it didn't help so I replaced the gauge, 5 years ago. I'm about ready to get a water and oil pressure and amp or voltage gauge st up that are all mechanical. I do not trust electrical gauges.
 
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Old Aug 29, 2004 | 01:38 PM
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GermanGuy
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Temp gauge problem

Hi Guys,
I had the same problem on my '94 F-150, 4x4, 302. Lucky I have a shop manual. The facts from that are:
1. on EEC engines there are 2 independent water temp sensors installed.
2. the one feeding the EEC is found above the thermostat housing (horizontal) and has 2 pins.
3. the one feeding the gauge (standing vertical with only 1 threaded pin) is hard to find between the intake manifold and the driver side valve cover.
4. to check the gauge, connect the gauge lead (has only 1 pin) to ground. The gauge pointer should move to Max. (H).

I followed this procedure and found my temp gauge okay, so I replaced the sensor. Now the pointer stays normally on the "o" of "Normal".

LoL Dieter
 
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Old Aug 29, 2004 | 09:34 PM
  #5  
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Originally Posted by GermanGuy
Hi Guys,
I had the same problem on my '94 F-150, 4x4, 302. Lucky I have a shop manual. The facts from that are:
1. on EEC engines there are 2 independent water temp sensors installed.
2. the one feeding the EEC is found above the thermostat housing (horizontal) and has 2 pins.
3. the one feeding the gauge (standing vertical with only 1 threaded pin) is hard to find between the intake manifold and the driver side valve cover.
4. to check the gauge, connect the gauge lead (has only 1 pin) to ground. The gauge pointer should move to Max. (H).

I followed this procedure and found my temp gauge okay, so I replaced the sensor. Now the pointer stays normally on the "o" of "Normal".

LoL Dieter

On mine, a 1990 f-150 5.8/351W, the one on the intake manifold above the thermostat housing is the one that is hard to find. The one on the manifold by the driver's side valve cover is really easy.

Thanks, I didn't know there was a second one. Couldn't find it in Haynes or Chiltons.

 
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Old Aug 30, 2004 | 02:37 AM
  #6  
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GermanGuy
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Exclamation Correction to my previous reply.

Originally Posted by GermanGuy
Hi Guys,
I had the same problem on my '94 F-150, 4x4, 302. Lucky I have a shop manual. The facts from that are:
1. on EEC engines there are 2 independent water temp sensors installed.
2. the one feeding the EEC is found above the thermostat housing (horizontal) and has 2 pins.
3. the one feeding the gauge (standing vertical with only 1 threaded pin) is hard to find between the intake manifold and the driver side valve cover.
4. to check the gauge, connect the gauge lead (has only 1 pin) to ground. The gauge pointer should move to Max. (H).

I followed this procedure and found my temp gauge okay, so I replaced the sensor. Now the pointer stays normally on the "o" of "Normal".

LoL Dieter
4. Turn ignition OFF. Connect the gauge lead (has only 1 pin) over a 9.7 ohms resistor (10 ohms will do it) to ground. Turn ignition ON, now the temp pointer should move to the "H" mark. Make sure the fuse (in fuse panel) for the gauge is good.
Dieter
 
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Old Aug 30, 2004 | 12:59 PM
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Or just install a real temp gauge. The stock one is ridiculous - that big of a range isn't 'normal' by any stretch of the imagination.
 
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Old Aug 31, 2004 | 01:11 AM
  #8  
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w6pea
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I have been very seriously thinking about a set of mechanicl gauges instead of the electric ones any way.
 
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Old Sep 6, 2004 | 12:02 PM
  #9  
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mkbonnes
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Thanks for the great info re: the sensors!!!!!!!!! Found the problem, got it fixed!!

Really appreciate the help!
Thanks again
 
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