Temp Guage Problem Solved
07-06-2004, 04:49 AM
#1
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Temp Guage Problem Solved
For anyone who may be interested,
Earlier I had posted a message questioning about a faulty temperature guage. Basically, the guage was pinned in the red every time I turned the car on, even after sitting/cooling over night. The problem was obviously electrical.
I pulled the plug to the temperature sensor, to no avail. Thanks to a reply from IceShark, I learned that the temperature sender that is in circuit with the dash, is seperate. It is the two-pronged sensor, located about 2 inches closer to the firewall than the other sensor. Anyway, this is what i thought was interesting. I pulled one of the two wires that plugs into the temperature sender, but the needle did not drop. After much trouble shooting, I discovered (it is possible I am wrong, so if this is the case, someone please correct me) the way this sender works. I believe that the device uses the block as a ground. Skipping the sender, and grounding the wire with the thin clip (and open circuiting the other) caused the over-heat light to go on, while the needle stayed down. Grounding only the wire with the thick clip, caused the needle to pin all the way up, yet the red light did not come on. Grounding the wire with the thick clip (associated with the needle) with a resistance of about 250 ohms brought the needle up about half way. If im not mistaken, it seems like the temperature sender provides independant variable (temperature dependant) resistance to ground, for each of those two wires. And it is for this reason that removing only the wire with the small clip, did not move my temperature guage down. I had originally thought that the temperature sender just provided variable resistance from the wire with the thick clip to the other wire. Further, I thought that only pulling the one wire would send my temp guage down. When it didn't, it threw me back pretty good. At that point I had no Idea what part I was going to need to be ordering. Anyways, if this is informative for anyone, then great.
Earlier I had posted a message questioning about a faulty temperature guage. Basically, the guage was pinned in the red every time I turned the car on, even after sitting/cooling over night. The problem was obviously electrical.
I pulled the plug to the temperature sensor, to no avail. Thanks to a reply from IceShark, I learned that the temperature sender that is in circuit with the dash, is seperate. It is the two-pronged sensor, located about 2 inches closer to the firewall than the other sensor. Anyway, this is what i thought was interesting. I pulled one of the two wires that plugs into the temperature sender, but the needle did not drop. After much trouble shooting, I discovered (it is possible I am wrong, so if this is the case, someone please correct me) the way this sender works. I believe that the device uses the block as a ground. Skipping the sender, and grounding the wire with the thin clip (and open circuiting the other) caused the over-heat light to go on, while the needle stayed down. Grounding only the wire with the thick clip, caused the needle to pin all the way up, yet the red light did not come on. Grounding the wire with the thick clip (associated with the needle) with a resistance of about 250 ohms brought the needle up about half way. If im not mistaken, it seems like the temperature sender provides independant variable (temperature dependant) resistance to ground, for each of those two wires. And it is for this reason that removing only the wire with the small clip, did not move my temperature guage down. I had originally thought that the temperature sender just provided variable resistance from the wire with the thick clip to the other wire. Further, I thought that only pulling the one wire would send my temp guage down. When it didn't, it threw me back pretty good. At that point I had no Idea what part I was going to need to be ordering. Anyways, if this is informative for anyone, then great.
07-06-2004, 12:28 PM
#2
Nordschleife Master
Alex, the sender does indeed ground to the block. Those two wires are seperate sending signals which I really can't comment on as I'm not exactly sure what the signal values are supposed to be.
And this sender can fail in the open or closed positions. Mine failed like yours pegging into the red. Another Rennlister sent me an old sender that, as it turns out, failed in the opposite way. At that point at least I knew the sender was the problem and just got a new one. They are about $30 from the dealer. Problem fixed.
I'd send you these old ones so you could plug them in but I threw them away. My guess is you have the same sender problem so just get that. And be careful about the little aluminum crush washer on the sender or you will drop in down in some hard to get at area.
And this sender can fail in the open or closed positions. Mine failed like yours pegging into the red. Another Rennlister sent me an old sender that, as it turns out, failed in the opposite way. At that point at least I knew the sender was the problem and just got a new one. They are about $30 from the dealer. Problem fixed.
I'd send you these old ones so you could plug them in but I threw them away. My guess is you have the same sender problem so just get that. And be careful about the little aluminum crush washer on the sender or you will drop in down in some hard to get at area.
07-06-2004, 01:51 PM
#3
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I did replace the temperature sender with a new one, ultimately solving the problem. I appreciate your help IceShark. And yes, I did drop the crush washer, realizing it was aluminum when my magnetic tip would not fish it out for me. LOL. Thanks again.