Two types of coolant sensors?

[The_Handier_Man1]

From: OldEdBrady  (Original Message)
Sent: 12/11/2004 10:45 AM

The sensor is gone.  So, off I went to get a new one.  There is one if you have a gauge.  One if you have just a light.  I have both.  So, I've tried both.  The one for the light doesn't register on the gauge and vice versa.  Any suggestions?



From: denison
Sent: 12/11/2004 11:13 AM

Usually the sensor used with the light would be an on-off switch. It would go closed if you were to get it heated up, for instance to some temperature between 190-215f. The sensor used with the gauge should have a resistance that gets lower when it get warmer. If you put it in the freezer for a few minutes, then measure its resistance with a VOM as it warmed up you would see this resistance change. I have no idea what the values are, a few hundred ohms probably - dropping to a few dozen ohms when hot.
I know there are combined sensors that do both functions, but I think they all have 3 pins, or at least more than one. New fangled stuff!
It is possible the bulb for your over-temp light is either burned out, or has bad connections from having so little use. Your gauge could be on the fritz too, or have a bad connection. If your instrument cluster uses a flexible circuit car to make the connections to the gauge, it might need its little contacts cleaned off with a fine abrasive or the rubber used in pencils erasers.
What year is your RV that it has both indicators, and is the chassis a Dodge product, or Chevvy or Ford?



From: Sea Hag
Sent: 12/11/2004 11:18 AM

I see from your member profile you have a 77 with a 440 , it is helpfull if you post that when asking for sugeestions . There should be two sensors on the 440 , one on the top of the engine by the thermostat housing , this one is for the idiot light on the sensor panel to the left of the dash . The second sensor is on the front of the engine behind the alternator mounting bracket these is an access hole in the plate , this is for the gauge .( you can see a pic if the sensor location under timming marks disccusion that I posted ,and has recently came back up . )
   I wouln't trust the gauge as it's a guess at best , My OEM gauge was at 3/4 the way up when my light came on . I replaced the OEM gauge and sensor with an aftermarket manual temp gauge . I found that it was running about 250 degrees when the light came on .
    When I added the aftermarket gauge I wanted to keep the warning light also so I had to swap the sensor locations as the aftermrket sensor would,t fit in the original gauge location on the front of the engine . I placed the original idiot light sensor on the front and the gauge sensor next to the thermostat housing . I then took care of the overheating problems by flushing the sytem and replaceing the cloged radiator .     Sea Hag 



From: OldEdBrady
Sent: 12/11/2004 11:22 AM

The Whiny Beggar is a '77 Brave, Dodge 440.

Naturally, I'm not too sure about all this.  All I know is,  went out to crank her up, and as soon as the key was turned--engine not running--the temp gauge went straight to the top and stayed there.  So, my first suspicion was the sensor.  Pulled the old one out and went to two different places.  Both offered the one-or-the-other deal.  As I said, I ended up with both. 

There is only one electrical connection to it.  With the gauge type, the "Engine Temp" light stays on at all times.  With the light type, the gauge runs right to the top of the scale and stays.

It's driving me nuts!  How can something with a single lead cause one or the other to go wacko?



From: OldEdBrady
Sent: 12/11/2004 11:25 AM

Now THAT is information I can use!  I was aware of only the one that screws into the jacket.  But I still cannot understand how, replacing only the one can affect both the light and the gauge.  I'll just have to play around with it some more.

Thanks.



From: Sea Hag
Sent: 12/11/2004 12:15 PM

It sounds like maybe your just moving the other wire for the gauge or the wiring is breached somewhere . the one on top is for the light which is just a normally open switch that closes to a (- )ground  to activate the lamp when temps close the switch .when you install the gauge type sensor to Lamp wire it is sensing a ground sice it's sending impedance to (-)ground . Since it's not a full ground on the impedance type sensor it may be back feeding , Improper grounds can cause strange tings to happen .
   The warning lamp panel on my 76 has several lamps ( door , step , seat belts , Temps , Ect . ) but only two are connected to any sensors . the trans temp and water temp , maybe the oil pressure too . they all work off (-) ground and run through a timmed relay for a lamp test when you first turn the ignition on . Chech the pic in the timming pics diccusion on this board . there is a pic of the frount of my engine with the radiator removed . you'll see the second sensor above the timming marks in the Alternator bracket . I beliuve it's the second pic posted or look in my album I think there is one there too . 



From: OldEdBrady
Sent: 12/11/2004 3:45 PM

Problem resolved!  SeaHag gave me the information about the second sensor.  It wasn't precisely where described, but close enough.  Idiot light sensor in the right place, Gauge sensor in the right place, and it works just fine now.

Thanks to the replies.  Even those that did not directly bear on the problem are saved for future reference--just in case.



From: DaveVa78Chieftain
Sent: 12/11/2004 9:01 PM

For reference, here are 2 sensors for the oil too.  On the rear of the block, just forward of the electronics bracket (ignition module/regulator), there are holes on each side of the cam buttruss.   The driver side one is for the idiot light.  The passenger side one is for the gauge.  Thanks for the temp info Sea Hag.  Didn't know there were 2 of those also.  Haven't had any problems with temp monitor yet so had not looked into it.
You wouldn't know where to find a engine oil level sensor would you?  Mounts on the driver side of the oil pan.

Dave



From: Sea Hag
Sent: 12/12/2004 10:33 AM

Dave , I found the two oil sensors on the rear of the block when I added a aftermarket manual Oil pressure gauge last summer . the pressure sensors can be combined into one port with a tee fitting , sice they don't need to be submerged in  fluid like the temp sensors . this way you can keep your OEM gauge and add a manual type . I also thought about finding an oil temp gauge to add there . I was going to try to install the OEM water temp sensor in one of the oil ports (it would have to go down  into  the port ) and use the oem water temp gauge for an oil temp gauge , but ran out of fittings and time .
   I don't recall seeing a port in my oil pan for a sensor , The warning lamp panel has several lamps ( maybe eight or so ) but only a couple are hooked up to sensors . Must have been something added by Winnebago as an Option . I,m sure SunPro or one of the other gauge manufactuers have a liquid sensor that would work . are you sure it's for level and not temp ?
As the oil level would go down some with the engine running .  Sea Hag 



From: DaveVa78Chieftain
Sent: 12/12/2004 9:32 PM

The oil level indicator is a switch/light (hold for 10 sec) arrangement in the center console area (radio, tranny temp gauge, etc.), not the warning panel on the left side of the dash.  The sensor is on the drivers side of the oil pan.  The outer portion of the sensor was sheard off by a PO.  Have had no luck finding one so far.

Dave