86 Xt TURBO DASH TEMP. FIXABLE?

[ArtRat007]

i have a digital dash in my 86 xt turbo and ever since i got it the temp gauge
sits real high even though the engine is actually operating at normal temperature

and by real high i mean 2 bars from top.

I used a friends independent temp sensor so i know its not overheating.

I replaced thetemp sender/sensor that goes to the gauge and no change.

The whole car got a good going thru including wiring harness.

I've never had a car that ran better than this one. Dont really know why its reading high
maybe its just old and inaccurate. I know I could get an independent
temp. gauge and I WILL. but i wanna hide it where its not an eyesore. So
i dont really have a PROBLEM.... but the temp on the dash being so high
really bugs me. heres my question

If i build a RS232 to TTL
translator so i can get some kind of tuning program or something IF THERE IS ONE THAT WILL WORK FOR THE XT.

Can i trick my ECU into sending my dash a cooler signal so the gauge doesnt
read as high? Or is that not going to be a changeable parameter? Still
gonna use a independent temp sensor/gauge no matter what.

 

AND YES i KNOW THAT THE WATER JACKET WILL EVENTUALLY GO AND I SHOULD SWAP TO EJ YADA YADA I KNOW ALREADY!

THANKS FOR ANY INPUT
ALWAYS APPRECIATIVE
            
        

                   

[mr sarcastic]

Please elaborate how you used an independent temp gauge. Not saying I don't believe you, I'm not gonna be one of those EJ swap pushers. Just want to know where you mounted the sensor and all that....

[MilesFox]

The ecu does not communicate withthe dash gauge. the sensor for the gauge is a single spade terminal near the thermostat. the ecu sensor is on the back of the crossover pipe under the turbo.

 

It is possible you have the wrong sensor with the wrong resistance value. MAybe the terminal is corroded and giving different resistances.

[mr sarcastic]

Do the sensors for the digi dash have a different resistance from the regular gauges?

[ArtRat007]

Well if i remember correctly ( it was 4+ months ago i checked this out) I used two different methods one little temp. gauge that you just put the connector under a bolt so it directly touches the block measuring block temp. this was found to be ok when car was fully warm

 

then i used an infared heat reader about a week later and that was good too. I figured if the coolant was getting too hot so would the block and thats how i measured

 

MilesFox: thank you i did not make the connection in my head that the signal from that sensor only goes to the dash. Why did they do that anyways with the 2 different temp. sensors? why one to the dash and one to the ecu? one wouldnt do it for subaru or ?. Couldnt be the connector i replaced that and about 4 feet of wire behind it and my volt meter reads good but i could have the wrong sensor like you suggest I got mine off of ebay as I couldn't find it anywhere else

Edited December 10, 2013 by ArtRat007

[MilesFox]

It has always been this way, even up into 2nd gen ej soobs, and in the 200's they made a 3 pin sensor that was the ecu and temp gauge with a common ground.

 

In subarus past, i have swapped a carb motor in place of an ea82t and the dash gauge and tacho work the same outside of any ecu input, which is just there doing nothing in this case.

 

I do know for sure there is a difference inoil senders depending on gauge or idion light. For example, the carb motor's oil sensor in a gl-10 will make the idiot light stay on with pressure, and go off when pressure is low. 

 

So by that i would assume there to be a difference in resistance value. This i do not know for fact. With my experience with gl-10's the gauge semeed to operate in the upper range, but you would really have to be cooking to make it display red. I suppose this gives you breathing room with your engine temp so you at least become afraid and let it cool before it gets too hot to damage anything.

[ArtRat007]

hmmm I will see if i can find what my resistance value is suppose to be.  Yeah my display never goes in the read just reads high and stays put so your right I also thought of an easier fix hows about this for redneck.... I'll cover the top bars on the dash gauge with some paint or something so the top bars wont show! that will make it appear to read normal then I shall add a new analog temp guage maybe in the ashtray or somewhere covert. I just want the dash to look like it works perfect i can get accurate readings from add ons

 

Thanks dudes party on

[TomRhere]

I would suggest you clean/inspect all of the ground wires going to the engine along with battery terminals.

 

Temp sensor is the ground for the circuit, offering varying resistance to ground as temps change.  If connections are dirty, it changes the total resistance value, giving false readings.

[mr sarcastic]

Many manufacturers use 2 seperate sensors, one for the gauge and one for the ecu. One of my vw's has 3. One for the gauge, one for the ecu, and one to control the after run fan/pump. It has an electric water pump and it'll pump water and run the fan after the car is off so the temp won't spike.

[ArtRat007]

I would suggest you clean/inspect all of the ground wires going to the engine along with battery terminals.

 

Temp sensor is the ground for the circuit, offering varying resistance to ground as temps change.  If connections are dirty, it changes the total resistance value, giving false readings.

thats been done the whole wiring harness has been cleaned inspected and repaired all 90000 feet of it when i got it cause most of the wiring closest to the engine was stiff and fried, the windows wouldnt roll down,somebody butchered the stereo wiring,  and the tail lights had to be replaced.

[presslab]

The EA temperature gauge is very sensitive to differences in ground voltage.  Running loads (like headlights or the blower fan) can change the gauge reading due to the currents flowing through the ground wires.

 

Start the engine, turn on a bunch of electrical loads, and put a voltmeter from the engine block to a good ground on the body.  What kind of voltage do you see?

 

If your grounds look good add another, thick gauge, one.  I put one near the thermostat housing to an air cleaner bolt.  You can also add another ground right at the instrument cluster.  I did these and the gauge was much better although not perfect.  Once I converted to an EJ engine (and adjusted the gauge) this problem went away, as the EJ sensor is not as finicky.