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Finally got my new big block all fired up, took it out for a trial run yesterday, and everything is working quite well, other than the fact that the temp gauge is reading upwards of 250 degrees when the car is up to temperature. I was quite alarmed at this at first but I have an IR temperature gun, and it is actually running at 180 to 190. The gauge worked perfectly with the motor I pulled out last year, just wondering if they make different senders , and I might have the wrong one?
Last edited by Dave Cunningham; Jul 5, 2015 at 11:12 AM.
[QUOTE=Dave Cunningham;1589983722]Finally got my new big block all fired up, took it out for a trial run yesterday, and everything is working quite well, other than the fact that the temp gauge is reading upwards of 250 degrees when the car is up to temperature. I was quite alarmed at this at first but I have an IR temperature gun, and it is actually running at 180 to 190. The gauge worked perfectly with the motor I pulled out last year, just wondering if they make different senders , and I might have the wrong one?[/
Same thing happened to me when I replaced my 327 with a ZZ4. Im using a GM sender made in the 60s and it now reads 20* higher than before. Probably improved the continuity of the sender circuit when the engine was replaced. The accuracy range of 230*-250* however is spot on and thats really what counts.
Dave - Yeah, it can be a shocker to see the temp gauge up that high but that feeling of anxiety goes away (for the most part) when you shoot it with the IR gun and see it's quite a bit less. I helped my neighbor get his 66 L72 out of mothballs a month ago and noticed after idling for about 20 minutes and sounding fine, the dash gauge barely showed the needle rising above the first tick mark. Can't be right. The IR gun showed 205 instead. A lot of the sending units available these days read all over the map but one particular model seems to work fairly well. It used to be made by Wells and maybe still is but if you go to a place like Autozone, you won't be asking for a Wells TU-5 temp sending unit, they happen to call it the Duralast TU5.
Mike T - Prescott AZ
Dave - Yeah, it can be a shocker to see the temp gauge up that high but that feeling of anxiety goes away (for the most part) when you shoot it with the IR gun and see it's quite a bit less. I helped my neighbor get his 66 L72 out of mothballs a month ago and noticed after idling for about 20 minutes and sounding fine, the dash gauge barely showed the needle rising above the first tick mark. Can't be right. The IR gun showed 205 instead. A lot of the sending units available these days read all over the map but one particular model seems to work fairly well. It used to be made by Wells and maybe still is but if you go to a place like Autozone, you won't be asking for a Wells TU-5 temp sending unit, they happen to call it the Duralast TU5.
Mike T - Prescott AZ
I tried several TU5's as well as others. No luck with any of them.
I tried several TU5's as well as others. No luck with any of them.
MOST folks are happy with the Wells TU5 senders. The current AC DELCO replacements and reproductions are erratic, although a few places "guarantee" that they are accurate.
You can check the calibration before installation at a few different temperatures to see if they are accurate or "close". Involves a multimeter that can read resistance, and a small metal dish that you can immerse the bottom half of the sender and heat the water. Use a thermometer to get water temp and the multimeter to get resistance. Then use the calibration table in the FAQ Section to compare.
A bit more difficult than just buying and installing like we used to do when the senders were made by DELCO in Indiana or Ohio (USA).
Thanks guys, I did read something in the archives about not using thread sealant, which I did do, but I doubt that is the problem, I will see if I can find the one you guys mentioned and give it a shot.
Getting a good sending unit is pretty much a crap shoot. I tried 4 of them before I bought the Durolast TU-5. It is pretty much dead on according to my IR gun. Your results may vary. By the way, I put 3 wraps of teflon tape on my sender, and my sender works just fine. The threads on the sender easily cut through the tape and make solid continuity with the intake.
Solved it m y friend Tim saw this thread, and had three new senders that were sitting on the shelf, they are all different brands, but if you look closely , you can see they all were made by one manufacturer, anyway he had tested them all before hand , and I popped it in there this morning and it reads dead on what my gun does.
Is that your sending unit in the picture? If so, could you have a look at the bottom and see if it has the same markings as the ones in the picture below. I'm curious as I bought 3 sending units with 3 different brand names and they appear to be identicle. In fact, all 3 tested within 5% of each other for ohm values at certain temperatures.
I bought two sending units, one from Advance Auto and a TU5 from Autozone. Set up a test using a pan of water, a meat thermometer, and a multimeter. This is what I came up with:
Temperature Test (deg. to ohms)
203P (Advance Auto Parts)
100*-0
120*-0
130*-250
140*-232
160*-195
180*-151
190*-135
200*-120
212*-112
According to knowledgeable sources, you want 125 to 150 ohms at "normal" operating temp of 180*. The 203P is closer to this number so I chose it, and my gauge still registers about 20 degrees above that. So I added a 10 ohm resister in-line and dropped it to 190. Thinking about adding another 10.
Just because I'm curious I broke open an old one to see what makes it tick. Looks like a piece of metal rubbing on the terminal post. Hard to imagine anything so simple could be accurate.
Is that your sending unit in the picture? If so, could you have a look at the bottom and see if it has the same markings as the ones in the picture below. I'm curious as I bought 3 sending units with 3 different brand names and they appear to be identicle. In fact, all 3 tested within 5% of each other for ohm values at certain temperatures.
.
Mine has no markings/numbers on the bottom. I believe mine (bought at Auto Zone) is made by Wells and relabeled Duralast.
P.S. It's my understanding that the pipe tape is a no-no.
Leif - The threads of a sending unit will 'bite' into the threads of the intake manifold well enough to make a decent connection and the use of a sealant will basically just help fill the voids to hopefully eliminate leaks.
Mike T - Prescott AZ
Anyone (but me) wonder how accurate these $30 laser readers we all use and assume are god's word are?
I have one and it seems to be accurate, depending on the circumstances. For example, if I point it at the thermometer that is hanging in my shop, it appears to be dead on. But if you are pointing it at your engine, are you actually measuring the temperature of the water? I think not.
Temperature sender
