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Index > Engine/Drivetrain > Thread: Water temp sensor
Thread: Water temp sensor
Tom93R1


Redlining
Posts: 458
posted June 26, 2002 01:32 PM

Water temp sensor

I just started thinking about my water temp gauge now that summer is here and I really don't know how well my cooling system works. My gauge isn't hooked up and I have been trying to figure out what I need to get it working. I have found a wire that when grounded causes my temp gauge to read full hot. Does this mean the temp sensor should have a single wire connector on it? The sensor on the truck right now has a 2 wire connector, it was from the 12a that was on the REPU when I bought it. Can I make the single wire work with the 2 wire sensor? Can I buy a sensor from Checker or a similar place and expect it to work? Do I need to find an ancient rx-something at a wrecking yard to get the correct sensor? What do you guys think is the best option for getting my temp gauge working again?

Maybe I just need to learn how a temp sensor works. Is it just a variable resistor that loses resiastance as the temperature goes up? If that is it then I should be able to just ground one terminal and connect my single wire to the other terminal, or are sensors all calibrated differently and that won't work?
thanks,
Tom

____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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Jeff20B


Moderator
Posts: 661
posted June 26, 2002 11:54 PM

When I first got my REPU running, my temp guage was not hooked up and read full hot. Then I hooked it up to the sender near the oil filter and it went down and read correctly. Only one wire. Maybe yours is a bit odd?

       
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tpfister


1st Gear
Posts: 22
posted June 27, 2002 12:15 AM

I bought a set of triple gauges with water temp, oil temp, and oil pressure.

       
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Tom93R1


Redlining
Posts: 458
posted June 27, 2002 08:31 AM

So the temp sensor is near the oil filter? What is the sensor that is in the coolant filler neck above the water pump? Jusst coolant level? Last night I got out my multimeter and hooked it to the 2 terminals on the sensor on the water pump and found that it was approximately 1 M Ohm when the engine was cool and resistance dropped when the temp went up.
Where near the oil filter in the temp sending unit you describe? Guess I will dig around some more tonight when I get off work.
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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Jeff20B


Moderator
Posts: 661
posted June 27, 2002 10:25 AM

The thing near the thermostat is for the choke control. It tells the magnetic choke position holder when to let go of the choke shaft so it'll pop in when the engine is warm enough. Mine works fine. The water temp 'thing' is to the left of the oil temp/light sending unit. This is directly below the oil filter pedastel. So look straight down from the filter and you'll see a cadmium plated round diaphram type thing with a single conection. Then look just to the left and you'll see a very small fitting with either a bullet connector or a quick disconnect (bullet is found on old engines and quick dis is found on newer). The colors are red or green or brown. I'm not sure what color mine is. I think the color denotes different ohms for different guages. My friend's '77 has a temp guage that always reads too high (it's even above the C when off so it needs to be 'zeroed' or calibrated, but he experimented with different colors and found one that was the most accurate, regardless of being offset as the guage is. I don't know which color he used). He has gotten used to it being 1/4 too high.

       
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Tom93R1


Redlining
Posts: 458
posted June 27, 2002 09:42 PM

I found the temp sending unit, hooked it to the temp gauge wire. Now when the engine is cool it reads about 1/4 hot and when I reach normal operating temp it is right about at the H. Then it hit me that I have an 86 motor with the temp sending unit from the 86 motor. My goal was to find out if I am running hot or if my temps were ok but now I guess I don't know anything more than when I had no gauge at all. Looks like it is time to just go buy a real temp gauge. Anybody know of any really cheap ones?
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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Jeff20B


Moderator
Posts: 661
posted June 27, 2002 11:11 PM

Just get a different color.

       
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repuguru


Redlining
Posts: 319
posted June 30, 2002 08:35 AM

Tom is the original engine harness intact on your truck or is it a 7 harness of some variety?
You must match the gauge in your truck to the proper sensor. The older motors had the single pole sensors. I think you can get them still from Mazda?
____________
77' REPU plus a few spare parts
for it.
85' GSL-SE
83' GSL

       
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Tom93R1


Redlining
Posts: 458
posted June 30, 2002 09:03 AM

haha, the harness is something the previous owner hacked in from I believe to be a 2nd gen rx7. It is really strange because the engine it had when I bought it was a 12a. The thing never had fuel injection so there are alot of extra connectors dangling and I really need to clean things up in there. I will ask the Mazda dealer what they can get me next time I stop in there. I seem to make a trip about once a month any ways. Hopefully the temp sender that is for the REPU fits in the same size hole as the 86 rx7 :)
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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Rotor


Revvin Up
certifiable rotorhead
Posts: 70
posted August 26, 2002 10:43 AM

Yes the threads on the sensors are the same size. You will need to get the correct year model sensor, as Mazda changed the voltage the instruments operate on. The wrong sensor will give erroneous readings. The correct sensor will have a post connector, not a blade.

Rotor

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ROTOR

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