AU Low Coolant Light - Not Sensor Problem

[Sfds]

Hi. I’ve checked past threads and I can’t seem to find this exact question having been asked. Apologies if it doesn’t warrant a new thread. I’ve an AU3 XR8 ute and the low coolant light is constantly on. Solid red light comes on about 10 seconds after starting. I’ve bought 3 sensors and checked each before fitting. All are OK, but the light still triggers. All 3 can’t be bad - especially as I “pre-checked” them. When I connect the sensor, but don’t have it installed in the tank, I can open and close the float with my hand and the light will correspondingly come on and go off, as expected. This tells me when I fit the sensor in the tank full of coolant, the light should not show. It might take a few seconds longer, but the light still comes on! Why does the light go on when I’ve checked that the sensor, float and wiring work as they should? I was wondering if I have a slightly warped tank as the sensors look to always sit as a very slight angle. (To me the slight angle seems far too small to make any difference.) I’m wondering if this causes some interference for the float against some internal plastic. Would anyone have an idea. I know I can zip tie the float to the sensor to make it work, but this defeats the purpose. I’m about to buy another Dayco header tank (same part as currently installed DET0002), but in case it’s obvious to someone that it’s something else, I thought I’d try here. Thanks for your suggestions. Cheers

[aussiblue]

Wiggle the senor wires with ignition on; the copper strands of the wires sometimes break inside the insulation especially at or near the connector near the reservoir.

[Sfds]

Thanks for the reply. I did try that, but no luck unfortunately. I tried 3 sensors and I could get each to turn off the light when I closed the float with my hand while being attached to the connector at the other end, so I assume the wires are OK. When I install the sensor within the header tank, the light still comes on. It doesn’t make sense to me. I’m wondering if something is obstructing the float from closing? I’m clueless, but I appreciate your reply as I’ve been caught by bad connections with wiring in the past. Cheers

[Sfds]

Thanks to those who took a look at this thread. I’ve done some more work this morning and found the problem. It’s the Dayco tank. There’s a manufacturing fault with it; a thin protruding seam of plastic lines the side of the “sensor chamber” and prevents the float from lifting. I poked my finger in the sensor hole of a genuine Ford header tank I got with one of the sensors. The sides were smooth … no interference for the float at all. By comparison, the Dayco DET0002 tank had a plastic protrusion that got in the way of the float doing its job. As best I could, I bent the seam down with my fingers. The sensor then worked instantly when I started the car. The warning light was off! Over time, I’m wondering if the plastic seam fault will move back to where it was and this time prevent the float from lowering if there’s a loss of coolant! I’ve had good stuff from Dayco in the past, but I’m disappointed in this header tank. This has cost me a bit in time and money, but the job’s now done.

[mad2]

Originally Posted by Sfds

Thanks to those who took a look at this thread. I’ve done some more work this morning and found the problem. It’s the Dayco tank. There’s a manufacturing fault with it; a thin protruding seam of plastic lines the side of the “sensor chamber” and prevents the float from lifting. I poked my finger in the sensor hole of a genuine Ford header tank I got with one of the sensors. The sides were smooth … no interference for the float at all. By comparison, the Dayco DET0002 tank had a plastic protrusion that got in the way of the float doing its job. As best I could, I bent the seam down with my fingers. The sensor then worked instantly when I started the car. The warning light was off! Over time, I’m wondering if the plastic seam fault will move back to where it was and this time prevent the float from lowering if there’s a loss of coolant! I’ve had good stuff from Dayco in the past, but I’m disappointed in this header tank. This has cost me a bit in time and money, but the job’s now done.

i did wonder if there was something 'blocking' it ........ but i wasn't sure so i said nothing