I cut down my donor car temp sensor to 13mm diameter(79 vette), cut M12x1.5 threads, but it leaked a bit, when I tightened - it broke (as others have done, I knew, I was even trying to be careful). Not much meat left after the turn down.

Anyway, I checked at autozone - a 98 vette/camaro temp sensor was only $17 made by Wells - model SU112 - correct M12x1.5 threads. I have measured the resistance betwen the two pins (not a three pin) and it seems to be up around 2900 ohms at room temp, then when put in boiling water (212F) resistance between the two pins goes down to about 210 ohms or so. This seems like a standard gauge sensor with approximately correct resistance values for my application so I figure I'll give it a try. If it works somewhat, but reads off, I could use either a serial or parallel resistor to get it close in the 210 range, and just ensure it goes hot when the thing gets hot.

But it would be nice to know the specifications of the sensor - is it in fact variable resistance? I have seen some posts here where folks say the sensor is a serial link - I think that is from the PCM to the gauge cluster, not the sensor. It could also be a voltage output sensor or something else - I can always check for dc, ac voltage, even put a scope on it.

Anyone out there know for sure what is up with this type of sensor? I searched the web hoping to find Wells temp sensor data, but no luck. I might try a local parts store, but one of them had another manufactor book, but it only listed some sensors values, and usually only one (e.g. room temp or so).

 

The 98 temp sender will work sorta. It does use a variable resistance scale like the old style gauges (thats why there are 3 wires, ground, PCM feed, and a gauge feed). From what I have read the resistance is close to the old style senders, but not perfect, so the gauge will work but it will not be perfectly accurate. I don`t know which way it errors to though.

It is the 99 and newer 2 wire senders that are serial data and send the signal to the computer not the gauge.

 

Hi

The factory manual has the resistance range for the temp sender on the L/H head listed somewhere in its (3) volumes -- sorry, I'm at work and don't remember just what manual section to look in. I'll look this evening.

For my swap, I just tapped out the hole in the R/H head and used the factory sender from my swap car. We tested its function to the guage on the dash and all is working properly. BTW, mine was 9/16-18, so it was easy to tap out from M12x1.5

Doing LS1 & T56 int0 '86 BMW E30

 

Thanks for the inputs. The wells (98 vette/camaro LS1) replacement temp sensor I got (SU112) only has two pins ( I was expecting three, but only two there). I was able to measure resistance changes wrt temp, between the two pins (nada from either pin to chassis/sensor threads-no ac or dc voltages or reistance changes).

Good idea re shop manual - I didn't think of that - I even have the 3 volume shop manual for my 98 C5 - it does provide a table of the resistance in ohms wrt temp (page 6-419).

-40F = 100,700 ohms
77F = 2796 ohms
104F=1459 ohms
176F=332 ohms
194F=241 ohms
212F = 177 ohms
(there are many more values below 176, only listed a couple of them - no idea why they list the sensor reads over 100,000 ohms at -40F - who cares?? any gage would be pegged to the left - <100F, guess it gives the engineers something to do, or maybe the PCM won't even let it start as the oil might be frozen ).

This is good news to me, as when I measured my old stock ~1/2" NPT temp sensor - I was getting about 180 ohms in a boiling pot of water (last test with Wells sensor was quicker, just a cup of boiling from the microwave, so it cooled fairly quick as it heated the sensor - probably why I measured a bit higher resistance). So this may be a great, low cost, solution. I'll repost after I install and see how it works. Can't beat the cost (I just got the right connector w/several inches of wire at the local auto wrecker yard from a recent GM vehicle for a buck).

Given I bought my 79 vette used, no guarantee the temp sensor in it was even correct, but it is what I have to go on for now.

When I finally get HP Tuners as planned (when $$ available), I will be able to compare my gage with the PCM reading from the dedicated driver side front of head sensor.

This reminds me - the C5 vettes digital display is referred to as the "DIC" - for driver information console or center - one can call up the coolant temp, oil temp, tranny temp, tire pressures, DTCs, etc. I always think that term is crazy, but maybe women vetter drivers get a kick of playing with their cars DIC while driving around .

 

I don`t think that they gave you the correct temp sensor. The 98`s should be 3 wire. I just checked autozones site and they do list the su112 for a 98, but they also list it for a 2001, and I know that the 98 and 01 use different sensors. You might want to check directly with wells.

 

Yes dont take Autozone on this one...as they are dead wrong on the 98 temp unit. They will swear up and down that 98 on up use the same temp sending unit...I spent a good 30 minutes one day argueing with an autozone employee that the SU112 is NOT for a 98...but for 99 and up only. Any other good autoparts place knows that 98 is different...just seems they cant get it right...even when confronted. So I just shook my head and walked out...never to go back yet. I got mine at Carquest...walked in and told him i needed a TSU for a 98 Camaro...he even smiled and said...having a hard time finding that one arent you. He even said...i bet you went to autozone to find it and they screwed ya. they must get it alot.

 

I agree this Wells SU112 might not be the correct 98 sensor - but it does seem to be a resistance only type sensor of correct size (M12x1.5) and resistance value based upon my measurements. That is all I am looking for ... it sure does not look like this unit is a serial output unit, nothing going on between the two leads and the case, only measurable effect is resistance between the two leads.

This confuses me - if everyone is right, and the two wire sensor only drives the PCM - I must ask if the PCM drive is really a variable resistor type vice serial digital, which would cost significantly more per sensor), and then the PCM drives a digital serial to the gage cluster.

This weekend I will check my driver side senor wire count, my 98 vette driver side sensor wire count, and install this SU112 in my 79 vette/LS1 and see if it drives my old style water temp gage quasi-correctly (based upon my measurements it looks very positive to me).

More to come....

 

Just wanted to update this - this Autozone SU112 temp sensor does work to drive my conversion car stock temp gage - it just reads high quite a bit. I can insert a 50 ohm resistor in series and the reading is back down around what should be right (~190-200F). I will just have to watch that it might not go as high as it should with this setup (just want some indication of temp, then when it goes higher will know to check whats up).
The ls1 I bought (standalone) had 853 heads and a two wire temp sensor in the driver side head, and my 98 vette also has a two wire temp sensors. Nott sure I have ever seen the 3 wire temp sensor (the oil press sender is 3 wires).
Works good enough for now, till I get a full set of matching gages. At least I have some feedback on temp for now.