'84 240Ti temp gauge erratic

Hello,

My water temp gauge in my '84 240Ti went nuts after it came back from
the shop.

The dial floats up to the top and stays there, as if the engine were
overheated to the max.

But it runs fine.

My clymer book says maybe the temp wire is loose.

I am looking all over the engine for the sensor screwed into the block
to see if the wire is loose but no luck.

Does anyone know where that sensor is?

Can it even be seen without taking some other part off and out of the
way?

Thank you.

Allan Ballard
89 240
84 240Ti

 

Drivers side of the engine under the intake manifold.

 

I'd put my money on the ol' degrading wiring harness. Check the
harness right at the firewall, I'll bet that your wires are bare and the
temp guage one is grounding out. Same thing happened to mine...

Bill

 

My water temp gauge in my '84 240Ti went nuts after it came back from

My '92 was doing that exact thing, and I flushed it, replaced the thermostat,
and the temp sending unit. ANd the hoses too I guess. That cured the problem.
I'm guessing it was the sending unit that was bad on mine (and yours)... but
mine was due for a cooling sytem overhaul anyway so I shotgunned it.

-jeff

 

It's under the intake manifold, in the middle of the cylinder head, just
above the block. It's got a single yellow wire going to it, and that
insulation likes to fall off. Check the integrity of the insulation at
the sensor, and near all the 8 pin plugs up on the firewall.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Do this with the ignition turned off. Take the wire of the temperature
sensor (which is fitted at the engine) and measure the resistance between
the wire and earth (the chassis). I'm not completely sure about this but
don't think it should read anything (no connection between the wire and
earth).

If it does, check the wire along its path into the cabin. On some cars the
heat from the engine makes the insulation on the wires cracky so it falls
off so the temp. wire gets in contact with earth. I don't know if the wire
is exposed to heat on a 240, but you should check that.

Also check the resistance on the temp. sensor itself by measuring between
it's connector and earth. It should probably be far above 20 ohm if the
engine is not very warm (Volvo 140's temp. sensor uses this range so maybe
it's the same on 240). Higher temp. means lesser resistance in the temp.
sensor.

 

I believe that's it.

The wires at the firewall are all almost bare.

I will tape them to see if temporary relief can be found.

Now the oil light is on, blinks a bit, but the oil is fine.

So what does this mean---that the car needs a whole new wiring
harness?

Allan

 

All 240's had this problem. The Swedes would not use wiring that had PVC
insulation. When it burns it gives off chlorine gas wich is deadly. The main
wiring harness from the firewall that goes under the intake turned brittle
and shorted out. It's usually where it makes the turn from the fire wall.
Cut the sheath back and inspect the wires. If not there, look for a bare
wire at the temp sensor. We replaced the harnesses under warranty until 1996
when Volvo decided they would
not to do it anymore.

 

The short answer is yes. The longer answer is that you can buy the
appropriate end connectors and piggy-back onto the existing loom and
avoid the several hundred dollar expense if replacing the harness would
be a significant portion of the value of the car.

Bill