ben a

i have ls1 from an 04 GTO in a 73 datsun 240z it is a project for the wife and she wants to keep the original gauges. so i got fuel and oil pressure and have a few options on water temp. There is not a lot of good info on this topic there is a lot of misinformation for example people say the three pin sending unit will send to an old gauge made to read ohms. the two and three pin units are on and off like a switch which is great for computers and idiot lights but not an analog gauge. i took the original 240z sender it checked it at 70 degrees and got 700 ohms and watched the DMM as the sender got to 200 degrees the resistance went down to 240 ohms. then i tried to find a sender that fits the ls1 passenger side threads with the same characteristics 700 ohms to 240 ohms. I found a few sites that list specs but so far no match maybe someone here has an idea. i can make a way to install the old sender in the water pump or drill and tap elsewhere but would rather just find a sender that fits. thanks

B52bombardier1

Autometer may have an adapter that should work for you. Have you looked at:

www.autometer.com

Rick

G Atsma

No way to adapt the Datsun temp sender to the LS with a brass fitting?

ben a

that is correct Datsun unit is to big. I found some senders the right size with varying resistance now i need to find a good match with decreasing ohms as it heats up.

blackhawkMC

Do you have large brass screw-in plugs on the sides of the block? They use those for the block heater, at least on some models. It's large enough to fit most senders.

Michael Yount

iTrader: (1)

Perhaps beyond the scope of your course right now -- but, I simply had fittings attached to the radiator - and screwed my stock Volvo/VDO sender in where the return rad hose attaches. Voila -- stock coolant gauge works like a champ. Similarly for oil pressure, oil pressure idiot light and oil temp senders -- found homes for all the stock ones so the stock gauges function normally with LS3.

ben a

nice car and yea I did use the stock oil pressure sender and the ls1 sender on a tee that I made so I could use the stock gauge. I can do the same with water temp sender. I will drill and tap someplace if I have to. there must be at least 20 pages of bad info I have read on this topic so far LOL people don't get that a gauge reads from cold too hot or low too high and ls1 senders don't send anything but off and on. a gauge needs a wax motor sender that read ohms from one point to another. factory gauges also ran through a voltage regulator that dropped them to about 8 or nine volts which helped keep from fluxing.

garys 68

iTrader: (1)

Agreed. The brass plugs on the side of the truck blocks can be drilled and tapped for 1/2" NPT.

ben a

not an option here dirty dingo engine mounts cover that area. 2004 gto ls1. what I am really looking for is info on who makes a sensor (wax motor type) that reads from cold 700 ohm to hot 230 degrees 300 ohms. with 12mm threads. I have found several companies that sell the exact type I need but they will not give the info on ohms. I have made phone calls and they say our senders are made to go with our gauges but yet they sell the senders separately and refuse to say what ohms they read.

Michael Yount

iTrader: (1)

I'll keep eyes/ears open for you Ben. There's likely stuff out there. On my VDO sender/oil temp gauge, I had a 12mm sender (gauge covers 100-300F) but the opening in the oil passage above the oil filter took a 16mm thread. Turns out VDO had the exact same sender, identical except 16mm vs. 12mm. So the replacement VDO 16mm sender screwed right into the oil pass on the LS block - removed factory plug, screwed in the sender. The bolt head underneath is the 'cross bolt' on the rear main.



Yeah, after reading exhaustively on the outputs from the ECU/senders and what was needed to translate, I finally decided that CAN BUS was more like CAN'T BUS for me, and just went analog.

supra8

I see they make a 1 piece replacement sender for the 240z. What are the chances of turning off the threads and rethreading to 12mm to go into the head? It worked on my Toyota sender.

ben a

I looked at that idea but the Datsun unit was too far off. even the bulb is too large. on the positive side I did just find what I needed. I read through some manufactures pdf cats and found the wax motor type with 12mmx1.50 threads with the ohm range needed for my gauge. there are also adjustments on the original Datsun gauges for calibrating. $15 ebay I will list all the info on this for other people to use once I test it. I actually found a few manufactures that have units that direct fit ls1 head and would work for many different stock gauges.

1964SS

iTrader: (1)

Not sure where you get this info, but it's incorrect as well. An LS1 oil pressure sensor works like any other sensor if there is an oil pressure gauge. I do know some sensors have a 3rd pin that does work like a switch for fuel cut off if there is low oil pressure so the motor will shut down.

ben a

your not saying what is incorrect. but you are agreeing that ls1 sensors are switches and that's the point of this thread that switches will not operate an analog gauge. so any info I have posted is just a fact that anyone who understands the difference between a thermo switch and a thermometer would get real easy.

1964SS

iTrader: (1)

No LS1 sensors are not switches. Some may have a switch built into them additionaly. It still has a working resistance like any other sender.

ben a

the water temp sensors GM uses on ls engines are called thermo switches and yes when closed they have an ohm reading of about 50 ohms. otherwise they are OL two wire or three wire water temp sensors on an ls have no ohm reading at all until they reach a certain temp then they close and have a constant reading. there may be some that have not seen yet but all the ones I have seen work this way. so if you know of some that have a starting point at lets say -10F to 220F that would be helpful.

6speediroc

iTrader: (5)

The 98 LS1 3 wire cts 12551708 will run a gauge properly..this is what I use for my 86 Camaro. Here is a reference for the resistance profile. It's pretty close to 240ohm at 200F.

https://www.thirdgen.org/forums/elec...lant-temp.html

ben a

thank you for that info I also found a bosch thermistor that has the 12mm thread and a close ohm profile. I was able to recalibrate my gauge to match the bosch thermistor. my gauges are stock 1973 Datsun 240z