Coolant temperature wiring

[Hollister]

Is there a way to get the coolant temperature guage working with nonstandard engine wiring / sender?

I have got a standard dash, uch and loom all the way through to the engine loom (so up to the big white block connector with the underbonnet relays/fuses), and want to try and drive the guage (nothing else matters).

Is it a case of 1 on the wires in the white connector block is a resistive earth for it, or is it (and i think it probably is) alot more complicated than that.

If the temperature guage worked the sane as the fuel guage it would be easy, but there doesnt seem to be any input on the dash for specifically the temp guage.

So any ideas? Either by using the existing block in the engine bay or by tapping into a wire doing into the dash display?

 

[Hollister]

Any ideas?

After a little more investigation it looks like it just works as a thermister, so there will be a resistance between two wires I can use, just need to find them.

I'm a little reluctant to just try shorting random wires together

 

[Matteh]

the temperature sender has 3 wires, a black (earth, via the ecu), white and cream

the white gives the resistance reading but it goes straight to the ecu. The cream wire goes to the plug and it *I assume* operates a coolant warning light? though I'm not sure

if it helps, I'm running a 172 engine in a mk1. If i connect the gauge wire to the white wire from the sensor then I get a reading, but I think it will be incorrect due to having 2 voltages passed over it.

So what I'm doing is leaving the original sensor in place and wired straight to the ecu and I'm going to plumb in another sensor into the thermostat housing just for the gauge (and warning light)



not sure if that helps? :S

 

[Matteh]

just to add, the resistance reading from the mk1 unit seems to be within tolerance of the quotes mk2 figures, so it could be viable?

the 2 pins on the mk1 sensor do the coolant warning light and the analog gauge... the sensor earths itself, so no need for an earth wire (but also means you can't as easily mount it in a rubber pipe

 

[Hollister]

Cheers, im doing more or less the opposite; a Mk1 engine in a Mk2. Everything will be fine ECU wise, its just I want to run the original guage. It has just proved impossible to trace the sensor back to the ECU

Ill be playing around with it more tomorrow anyway

 

[Matteh]

odd project ... why?

in that case the mk2 gauge gets its signal from the ecu, not sure if its the same readings as the sendor itself gives

if you have 1 wire from the gauge that is the signal wire, a good way to check it just ground it and see if the gauge shoots up to max

 

[Hollister]

odd project ... why?

in that case the mk2 gauge gets its signal from the ecu, not sure if its the same readings as the sendor itself gives

if you have 1 wire from the gauge that is the signal wire, a good way to check it just ground it and see if the gauge shoots up to max

Thats the trouble, the gauge doesnt seem to have any specific wires in the plug going to the dash unit unlike the fuel gauge. Ill just have to kep trying to find where the ecu gets its input from

As for the project, its http://www.cliosport.net/forum/showthread.php?t=264615

not a normal engine and gearbox

 

[ditz]

the gauge dosnt go to the dash mate.

it runs from the temp sensor straight to the ecu, gives the ecu a resistance reading across its 2 wires, then from the ecu it goes in to the cluster.

 

[ditz]

oh, and with the temp sensor unplugged the ecu thinks its -40 degrees, but the fan failsafes in the ON position.

 

[Matteh]

ah ofc, I remember reading your thread

I need that gearbox in my life :dapprove:

 

[Hollister]

the gauge dosnt go to the dash mate.

it runs from the temp sensor straight to the ecu, gives the ecu a resistance reading across its 2 wires, then from the ecu it goes in to the cluster.

Cluster?

It's the wires going to the ECU i really want to identify in the big bundle of wires I have left.

The fan and is seperately wired anyway, so no trouble there