Aftermarket temp gauge

Pav · Post by **Pav** » Sun Feb 21, 2010 11:20 pm

Hi, I want to run an aftermarket temp gauge in my L series (EJ20), and was just wondering if I could just connect it straight to the ej's temp sender? I can't find any wiring diagrams specific to my engine (98 ej20, ecu has single connector with a 10mm bolt in it) so I don't know where the temp reading output is?

Also, the original L series radiator has 2 sensors in one of the side tanks, what are these for? Are they also temp senders? Could I hook up the gauge to one of those?
I can't really use a sender in a sleeve for the top rad hose because it is way too short already, unless the sender can be mounted in another way?

GOD · Post by **GOD** » Sun Feb 21, 2010 11:52 pm

The gauge has to be matched to its correct sensor.

EJs have two sensors - one with a two pin red plug which sends a signal to the ecu, and a brass one with a single (green white?) wire for the original car's temp gauge. You can remove the gauge sensor and replace it with the sensor for an aftermarket electronic gauge. Pretty sure the thread is 1/8" NPT. Older-type mechanical gauges have a wire probe as the sensor, which you can slip into the top hose.

Dane.

Pav · Post by **Pav** » Mon Feb 22, 2010 12:11 am

Ah cheers that'll make things easier...

Also, the car has two aftermarket thermo fans wired up, although I'm not sure what triggers them? Is it the ecu in an ej car? What would trigger them in a standard L series? And how would I wire up a switch to bypass the trigger so I can turn the fans on when I want?

GOD · Post by **GOD** » Mon Feb 22, 2010 1:06 am

L series have the fan triggered by a switch in the driver's side header tank. Not sure what your second switch/sensor there would be. EJ cars' fans are switched by the ECU.

This is how I've got my fan override set up:

Pretty sure the fan wire out of my ECU (96 EJ18 Impreza) was red/green. Newer ECUs have two independently switched fans, which gets more interesting.

Dane.

Pav · Post by **Pav** » Mon Feb 22, 2010 1:14 am

Thanks for that, really helped, now I can finally monitor/control my cooling system properly

drof351 · Post by **drof351** » Mon Feb 22, 2010 8:48 pm

The factory relays are still connected to the ecu turning them on and off.

Pav · Post by **Pav** » Mon Feb 22, 2010 9:56 pm

So the ej's ecu switches the fans on aye? So those two sensors on the l series radiator do nothing at the moment?

drof351 · Post by **drof351** » Mon Feb 22, 2010 10:11 pm

Are the plugs on the ea82 radiator plugged in? Yeh follow the wires from the fans to the relays. They're still earthed by the ej ecu running of the engines thermo fan switch.

daza · Post by **daza** » Tue Feb 23, 2010 4:07 pm

Have a look at this,
A few members have them and are very happy with them, simplest thing to hook up too.
NB, Not recommending this seller particularly, just the item.
Daza.

Pav · Post by **Pav** » Tue Feb 23, 2010 7:36 pm

Yeah, I checked out that engine watch dog thing, seems quite good and I'll probably mount it later on as a backup.

I found the single wire temp sensor in the EJ's coolant passage thing, but the gauges I was looking at buying had different sized threads... Can I hook up this sensor straight to the L series gauge? I understand that it will read half as much as originally as it is calibrated differently?

Pav · Post by **Pav** » Tue Feb 23, 2010 7:45 pm

Also, which connector block/wire is the L series temp gauge (in the engine bay section)?

steptoe · Post by **steptoe** » Tue Feb 23, 2010 9:36 pm

engine temp and oil is in the same connector as the injectors and nearly every other wire that goes onto the engine

YouTube · Post by **El_Freddo** » Wed Feb 24, 2010 8:18 pm

Pav wrote:Also, which connector block/wire is the L series temp gauge (in the engine bay section)?

That will depend on wether or not your L series engine wiring was just disconnected from the EA motor wiring or if it was cut then taped up out of the way neatly. If you've got the plug near the subi's right hand side strut tower and the engine wiring it will be easy to find the temp guage wire - it'll be a flat blade female connector, there is two of them, one oil (yellow) the other is the temp guage. This goes for carbie or MPFI/MPFI turbo EA82 motor looms.

The L series guage will read about half of what it should. I have recently read that this can be fixed with a 1/4w 270 ohm resistor wired in line near the temp sensor. I'm yet to confirm this but am keen to give it a go.

The other way to tap an after market guage in is like this, its a mechanical guage that's tapped into the heater hose, coolant out to heater core:

Pav wrote:So the ej's ecu switches the fans on aye? So those two sensors on the l series radiator do nothing at the moment?

If that's how you've wired them in. I don't know of two sensors in the L radiator, only one in a standard radiator... I've got my only thermo fan wired in like this:

When I get a second thermo sorted I'll have the auto side of this triggered by the ECU, so I"ll have one fan from the temp of the radiator and one from the ECU. It'll be interesting to see the difference in switching of each fan in different conditions.

Cheers

Bennie

Pav · Post by **Pav** » Thu Feb 25, 2010 11:02 am

Lots of great info there that I didn't find in the usual ea to ej conversion write-ups, you should write up your own one

But yeah, I've decided to remove the ej's single wire temp sender and replace it with an aftermarket sender/gauge that I found on ebay.

The diagram with the thermo fans, how would I wire up a 2nd fan (nothing fancy like different speeds or anything) Would i need a 2nd relay?
Cheers for your help

Pav · Post by **Pav** » Fri Feb 26, 2010 7:01 pm

is it ok to wire up two fans like this using a single relay?

drof351 · Post by **drof351** » Thu Mar 11, 2010 8:36 am

No that won't work, you've got earth to both side of the switching part of the relay. Also ideally they run a relay for each thermo due to the current draw. Why not just copy whats there? Its got 2 relays switched by the computer. Then you still have hi and lo and if you connect up the air con it will be turned on by the computer. Why do u want a switch?

GOD · Post by **GOD** » Thu Mar 11, 2010 9:03 am

drof351 wrote:No that won't work, you've got earth to both side of the switching part of the relay. Also ideally they run a relay for each thermo due to the current draw. Why not just copy whats there? Its got 2 relays switched by the computer. Then you still have hi and lo and if you connect up the air con it will be turned on by the computer. Why do u want a switch?

It will work, it's just that the diagram is a bit confusing with the yellow/black and blue/red wires disappearing into a mystery box.

Blue/red needs to go to ignition positive, yellow/black goes to ECU (or fan switch in a stock L) switched earth.

Dane.

Pav · Post by **Pav** » Thu Mar 11, 2010 1:10 pm

Yea atm I have the ECU running the fans quite well, but would like to have a bypass switch maybe as added insurance to not give the motor a chance to heat up too much in extreme situations, I've got it basically figured out now.
Also what do you mean by hi and lo (fan speeds?) and does the computer control that?

As for the aircon I've just chucked it all out (cos I got the fans on the grille side due to a larger rad) and I've never had a car with aircon even on 40c+ days so it doesn't bother me.

drof351 · Post by **drof351** » Thu Mar 11, 2010 10:55 pm

But the computer won't let it overheat? even in extreme situations? If its hot the fans will be on. If it gets hotter the fans will stay on?

Pav · Post by **Pav** » Thu Mar 11, 2010 11:13 pm

Fair point, but it's easy to wire up a switch anyway (I could also switch the fans to OFF in case of a river crossing? lol)
Sometimes it just takes a while for it to cool down, I've chucked in a MY radiator for now that is in sorta ok condition, but I think I am going to fit a new lib radiator for peace of mind.
Also, those thermo fans that are in there atm, are they aftermarket?