MX83 Temp Gauge with 1JZ

[RollaBabe]

Hey all
After being ****ed by my wiring guy I'm trying my hardest to get things working.
I'm having some probs with the water temp gauge from the factory dash.

Here's the situation.

I tracked down the sender wire from the gauge. When earthed gauge went to hot instantly. I bought a brand new MX83 temp sender and a speco top hose adapter with the same thread (16x1.5). The adapter is for a mechanical gauge and as such didn't have a hole to screw an earth point into so I made one.

Multimeter reading from the top of the sender to the earth point (or anywhere on the adapter) with engine at operating temp is 65 ohms.

Now the drama

As soon as I connect the signal wire to the temp sender the gauge goes straight to hot even though I know for a fact the coolant isn't that hot.

Can anyone shed some light?

Any help or ideas greatly appreciated.

[Robbos_Toyotas]

when you say you have a hose adapter, did you put the sender in the hose or to something earthed on the motor?

[RollaBabe]

when you say you have a hose adapter, did you put the sender in the hose or to something earthed on the motor?

The sender is housed in the top hose using one of these:
. This adaptor is then earthed to the block using a small screw like the one next to the sender hole.

[Mos]

Multimeter reading from the top of the sender to the earth point (or anywhere on the adapter) with engine at operating temp is 65 ohms.

I'm not exactly sure what the sender should be doing, but I think that's too low.
I think it should be closer to about 200ohms at 100degrees but I can't find the docs at the moment.
How come you're not using the 1JZ sender?

Mos.

[RollaBabe]

I'm not exactly sure what the sender should be doing, but I think that's too low.
I think it should be closer to about 200ohms at 100degrees but I can't find the docs at the moment.
How come you're not using the 1JZ sender?

Mos.

Just had a look at work and have found that the 7M runs a coolant temp sender as well as the gauge sender. Perhaps this sender is in the same circuit which would increase the resistance to the gauge. Then when you lose the coolant sensor you lose resistance and the gauge fails to operate correctly.

I'm not jusing the 1J sender cause i wasnt certain it would work with the X8 dash.
+ It seems any wiring info I can find is close but not spot on.

[RollaBabe]

I think it should be closer to about 200ohms at 100degrees but I can't find the docs at the moment.


Mos.

All my info tells me 184ohms cold -17ohms hot. I'm over it. Might as well bite the bullet and chuck in an aftermarket. Jus't didn't want the fooli sick gauges all over my car look.

[CrUZida]

Yes, all motors pre mid 90's use 2 temp sensors.
One directly for the ECU (the 2 wire one) , and one directly for the guage (the 1 wire one).
This applies to both the 1JZ and the 7M that was in there before. The gauge sensor will be identical between the two (even if it looks different, its charateristics will be the same).

65ohm's is roughly 88-89degC, so thats perfect for normal running temp. The MX83 gauge should be in the middle if its all working right.
Its one wire directly from the back of the gauges, through one of the dash-to-engine-harness plugs, and down the engine harness to the single wire sensor. Its a yellow wire with a green stripe.
You don't need that adaptor you've installed as the JZ motor will have a sensor on it.

FYI, 184ohms is roughly 60degC.

[RollaBabe]

Awesome info... still doesnt explain why my gauge won't work though....

[CrUZida]

I'd presume you'd have a short somewhere in the system.

[RollaBabe]

No go. I have run a brand new wire to the aftermarket sender with no difference whatso ever. As soon as its connected gauge goes to max.I'm gunna bang an el cheapo mech gauge in for now so i can drive it till a mate gets back in the new year. He should be able to sort it out.

[CrUZida]

Could be a faulty dash I suppose ?

[RollaBabe]

Jus bizarre coz it worked perfectly before i started the conversion. Its got me scratchin my head bigtime. Thanks for your help though

[CrUZida]

Hmm, very strange. I feel your frustration.

[Robbos_Toyotas]

maybe the eart wire isnt earthing properly or something...god knows...does the temp gauge go down when the cars running like as if its working in reverse?

have u thought of doing the jzx81 cluster swap? its a digidash but they look good and work with 1 and 2j sensors...this is how i got all the things on my 2j mx83 like tacho, temp gauge, electronic speedo etc to work...its quite an easy swap as it all bolts in and they r cheap as chips....just an option?

blake

[lexsmaz]

When the car is cold & the temp sender connected does the gauge read low or still high

When you disconnect the wire from the sender unit, i pressume the gauge reads low ? ..

[1jzfanatic]

so have you changed any pins in relation to this? (i only put the question mark beside the top 2 cause i cant remember whether they were the other way around.)

if so, and it still goes to hot, have you tried running a makeshift wire from the second one,(the sensor) straight to the white plug the in the loom for the dash? could be that the sender wire might be earthing out somewhere,(might be cut/split) if its touching ground where it shouldnt, it will go hot instantly....

hope that helps

[RollaBabe]

I have run the a new wire to the sender from the back of the plug that goes in in that picture. The signal wire I used was the left most wire. I used this because when I eathed it out the gauge went to hot instantly.

Lexsmaz the gauge goes to hot as soon as the ignition is turned to on even if the car is stone cold. And yes as soon as the sender wire is disconnected it drops straight to cold.

[Mos]

Have you hooked the earth up? (the gauge has its own earth, directly on the engine)...

[RollaBabe]

So earth the bottom pin and it should go to correct reading possibly? I'll give it a try. I'll try anything.

[Mos]

If it's not connected you won't get correct operation. It's there to increase the accuracy of the gauge by not having any other currents running through the same ground.