On my 1961 corvette I just put in a new Harrison repo radiator, replaced the water pump as long as I was in there and put in a new temp. sending unit. Now my troubles start. I started the car and within 2 or 3 minutes the temp. gauge is pegged. The gauge worked fine before. This is a AC Delco sending unit. Thinking maybe it is a wireing problem, I ran a separate wire from the sending unit to the gauge. Same thing, pegged the gauge. At this point the engine is still not hot, I can touch it. So now I replaced this AC Delco sending unit with a NAPA one. Same thing,pegged the gauge. Now I get a mechanical temp. gauge, no wires needed, start the car and life is wonderful. This gauge reads a perfect 180 degrees. So the new sending units don't like the old gauge. Now what do I do? By the way I already tossed the old sending unit. Do I try to find a NOS sending unit or visit a junkyard and try to get one off a 40 year old engine. Thanks for the help. John Mashak
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Re: temperature sending unit
Go to Autozone and get a Wells TU5 Temp unit. ($6.00) Prior to installation check the resistance at room temp. It should be about 700 ohms.No guarantee, but with most C1's this will give an acceptably accurate temp reading. -
Re: temperature sending unit
Go to Autozone and get a Wells TU5 Temp unit. ($6.00) Prior to installation check the resistance at room temp. It should be about 700 ohms.No guarantee, but with most C1's this will give an acceptably accurate temp reading.Comment
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Re: temperature sending unit
There have been several recent threads on this. I noticed them as I had the same problem. The new sensors are different than the old ones and will make your gauge read way too high.
You can put a resistor in the circuit to bring it down. It will read correctly at only one place and be off by a couple degrees everywhere else. This is not bad because the correct setup is not very accurate either.
Or, find an old one. Someone has 6 of them on ebay on a Dutch auction now. Mary Jo also sells them. I got one from her that was not quite right, but much better than the new Delco units.
Good luck!
Dave ChristensenComment
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Re: temperature sending unit
There have been several recent threads on this. I noticed them as I had the same problem. The new sensors are different than the old ones and will make your gauge read way too high.
You can put a resistor in the circuit to bring it down. It will read correctly at only one place and be off by a couple degrees everywhere else. This is not bad because the correct setup is not very accurate either.
Or, find an old one. Someone has 6 of them on ebay on a Dutch auction now. Mary Jo also sells them. I got one from her that was not quite right, but much better than the new Delco units.
Good luck!
Dave ChristensenComment
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Be very careful with resistors
The trouble with the resistor regimen is that you get the gauge to read right at one temperature. It is not a direct linear relationship. The end result is that your gauge may not read properly in an overheat situation, which is what the gauge is there for to begin with.Comment
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Be very careful with resistors
The trouble with the resistor regimen is that you get the gauge to read right at one temperature. It is not a direct linear relationship. The end result is that your gauge may not read properly in an overheat situation, which is what the gauge is there for to begin with.Comment
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Re: temperature sending unit
John -
Sounds like they gave you a temperature "switch" (for an idiot light), not a variable-resistance "sending unit". The Wells unit from AutoZone works pretty well, or an old one from Mary Jo.Comment
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Re: temperature sending unit
John -
Sounds like they gave you a temperature "switch" (for an idiot light), not a variable-resistance "sending unit". The Wells unit from AutoZone works pretty well, or an old one from Mary Jo.Comment
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Re: temperature sending unit
The Wells unit will read "temp switch", but it is in fact a variable resistance sender. BTW, I have no financial interest in Autozone or Wells. I keep recommending these simply because I know they work.Comment
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Re: temperature sending unit
The Wells unit will read "temp switch", but it is in fact a variable resistance sender. BTW, I have no financial interest in Autozone or Wells. I keep recommending these simply because I know they work.Comment
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Check the 'nest'....
Principal is simple, wiring is B+ to gauge, then home run wiring out to temp sender and ground. The gauge is simply an ammeter. To 'peg' the gauge, it has to be seeing near zero-ohm resistance to ground (at least below 40 ohms) and this could be happening in several ways:
(1) Sender is bad and/or incorrect.
(2) Sender is installed incorrectly (some kind of 'coating' allowing short to ground across bakelite insulating tip of sender).
(3) Wire from gauge to sender is breached and grounding somewhere.
(4) Gauge is installed improperly and is shorting to ground at the dash.
Sooooo, go trouble shoot the issue....
(1) Disconnect all wiring at the temp sender. Put your ohmmeter on it and look at it's resistance profile to ground. Should vary between, say, 1100 ohms dead cold to 40 ohms (overheat-engine going into thermal runaway).
If the sender checks out, move upstream.
(2) What does the gauge read when the temp sender wire it TOTALLY disconnected (should sit at dead cold position)? If it doesn't, the problem is in the gauge itself and/or your installation of it in the dash.
(3) The third is pretty simple and you've kinda done that already buy substituting an alternative wire run to the temp sender, but you did NOT state the alternate wire you put in went in with the original wire run REMOVED, so ohm the sender wire vs. ground with it DISCONNECTED on both ends. You ought to see infinite resistance....Comment
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Check the 'nest'....
Principal is simple, wiring is B+ to gauge, then home run wiring out to temp sender and ground. The gauge is simply an ammeter. To 'peg' the gauge, it has to be seeing near zero-ohm resistance to ground (at least below 40 ohms) and this could be happening in several ways:
(1) Sender is bad and/or incorrect.
(2) Sender is installed incorrectly (some kind of 'coating' allowing short to ground across bakelite insulating tip of sender).
(3) Wire from gauge to sender is breached and grounding somewhere.
(4) Gauge is installed improperly and is shorting to ground at the dash.
Sooooo, go trouble shoot the issue....
(1) Disconnect all wiring at the temp sender. Put your ohmmeter on it and look at it's resistance profile to ground. Should vary between, say, 1100 ohms dead cold to 40 ohms (overheat-engine going into thermal runaway).
If the sender checks out, move upstream.
(2) What does the gauge read when the temp sender wire it TOTALLY disconnected (should sit at dead cold position)? If it doesn't, the problem is in the gauge itself and/or your installation of it in the dash.
(3) The third is pretty simple and you've kinda done that already buy substituting an alternative wire run to the temp sender, but you did NOT state the alternate wire you put in went in with the original wire run REMOVED, so ohm the sender wire vs. ground with it DISCONNECTED on both ends. You ought to see infinite resistance....Comment
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