I just finished putting my car back together, and my thermosensor is dead. I just wanted to make sure that I plugged the right wire onto the thermosensor that is in the back housing, below the oil pedestal.

I know it seems like a dumb question, but as I am getting no signal from the sensor I just wanted to double check everything.

I have an aftermarket gauge, but like to have the commander and OEM gauge as warnings/backups.

thanks for the help.

-Josh

 

The Thermosensor on the back of the Water Pump housing is not the one for the stock temp gauge.

Is your stock temp gauge not reading anything or is it really the thermosensor that is havingt he problem?

 

sorry, i wasnt clear i meant on the back engine housing. the little tiny one under the oil filter pedestal.

my gauge reads nothing. that is why I think it may be a wiring problem. The Commander reads nothing and the OE gauge doesn't move.

 

If the PFC isn't reading it, then it's most likely a dead sensor or damaged wiring. I really haven't seen anyone having a problem with those senders before. I guess it's possible you might have damaged it.

 

my suspicion is a break in the wire, but i am going to order a new sensor from malloy's just to make sure. I will get under the hood and check continuity on the wire this weekend.

the only reason i originally posted was to make sure i was tracing the right wire.

 

I don't think the PFC gets it reading from that sensor either. I had mine hooked up incorrectly and i still got a commander reading. However the stock gauge did not work. I'll go out and look at the wire color in a bit. It is a single lead wire with the female blade connecter on it.

Is the sensor behind the WP housing hooked up correctly. Those plastic connectors like to break if you look at it wrong. The wire going into that one i have also had break off flush with the plastic and "look" like everything was fine, but the wire was not making a circuit anymore.

 

i will double check both of them. my gauge is dead, and my PFC.

so you think the PFC gets its signal from the green one on the back of the waterpump housing, and the stock gauge gets its signal from the one on the back engine housing?

could be a case of bad wiring. i reused my harness. i checked everything for continuity when it came out, but something could have broken on the way in. if it is that, then i suppose i got lucky it is only the temp sensor wire(s). everything else seems to be running great.

 

is the oil pressure gague working?

 

yep. no problems with the pressure gauge.

i just played with it for a little while. the wire i have hooked to it is a brownish/tan wire with a silverish/white stripe. it seems to have continuity as fast back as i can measure. so i guess the sensor is gone.

i also checked the other two sensors on the back of the waterpump housing and they seem to be ok for continuity as well.

at this point i would be satisfied to think that it is the sensor, however, what dave(bigisland) said has me a little confused. does the PFC use the sensor on the back of the waterpump housing for its signal. if so it doesn't make sense to me how both sensors could be bad.

 

does anyone have the specs for testing the bastard? i guess i could check my shop manual, and i will, but i just wanted someone to hold my hand.

 

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/water-thermosensor-install-398679/

The sensor on the back of the filler neck is the one for the PFC. When my sensor went out my stock gauge still worked fine.

 

thanks for all the help guys. i tested the sensor and the green thermosensor on the back of the WP housing is withing specs. therefore, it must be wiring.

my dad mentioned that i should check all my grounds, and then possibly make a jumper harness and plug the sensor straight to the ECU. i am gonna try that this weekend.

now that i know which sensor it is, I can continue to chase the gremlin.

i still wish i woulda bought a new harness, but damn $700 is a lot of money.

here is another question, is this the same sensor that controls the fans, or is it the black one below it? I have been grounding the fans to run continuous, so as not to risk an overheat.

 

Make sure you check for continuity at the sensor end TO the ECU. It may have a break somewhere inside the big rapping cluster of wires.Terminal 3E at the ECU is the "engine coolant temp sensor" Pg.Z-32 in the FSM "engine control page" It is a Br/B wire and seems to share quite a few components off that wire. You may have another issue that is masking itself as a temp sensor problem.

Does the PFC screen work at all? If so go to the sensor/switch check screen and see if any are highlighted in black. If so, that is a good place to start the hunt. Instead of speculating at first. Which is what it may come down to. ...trial and error.

The water thermoswitch is the one that controls the fans operation That is the round black connector if i recall.B/R wire going to it.

 

thanks dave. the PFC screen does work, so i will try and do the sensor check. i didn't think of that.

 

No problem, I often overlook the simple way of doing things, only to kick myself in the *** after i finally figure out how stupid i was Hopefully it will be as easy as looking there and going to the bad unit. Good luck.

 

he already said the commander does not read anything....

 

Originaly posted by Josh(the thread starter):...thanks dave. the PFC screen does work, so i will try and do the sensor check. i didn't think of that."




care to take back that statement?

I understand that the temp reading is not showing..."that" is what we are trying to figure out

 

by anthing i thought he ment any temp reading. not that it did not work at all which would be a seperate problem. if it is not showing any change in temp on the screen what diif will the sensor check screen make? unless the commander screen showed the temp as some weird unknow number because of the open/short but i would assume that would be pretty self evident

 

If there is a sensor that is not functioning properly( giving the proper voltage reading to the commander) the PFC shows that as a "highlighted" sensor in the switch/sensor check screen. It is actually very helpful when looking for a needle in a haystack so to speak.

it will be the sensor abrivviated by the " WTRT" It should show a voltage reading within a specific range. The FSM should say what that range is in a troubleshooting table. Then you compare and start checking things on that circuit.

Pretty cool tool the PFC. I think it is one of the BEST things anyone can do to these cars regardless of the # of mods. It is a great troubleshooting tool when it needs to be.

 

Josh,

Dollars to donuts that you swapped the connectors with the fuel thermosensor.

They have the exact same connector and you can easily mistake them/swap them when reinstalling a motor.

I didn't do this but I spent a half an hour on the phone convincing someone that because their car was cutting out at 3000rpms and their fuel temp was off the charts "---" but water temp was a steady 19 degrees C despite the fans running that they swapped them...after I dug through the manual to prove my point they relented that my theory was correct and saw the faded colors on the wires didn't match where they were supposed to be plugged in...

(If this is the case, thank technonovice for pointing our your thread 'cause I don't read the FD3S section...too much noise for my tastes...)