I have often wondered why our Mk 1 16TRS Auto didn’t come with a low-level coolant warning lamp, especially as the cooling system is used to remove heat from the auto box via the cooler/heat exchanger and a failure there could cause water to be lost quite quickly.
Recently I’ve seen several other Mk1 Autos and they are the same although manual MK1s seem to be fitted with the warning light, control box and sensor.
On eBay I found a genuine BX low coolant level warning kit (ZC9000125T, eBay item No 165165396122) and bought it to see if I could fit it. The kit consists of the sensor (2 prong type), control box, wiring loom and various connectors (also a hose pipe and jubilee clips that seem totally unrelated).
The wiring loom has two connector plugs. One is a 5-pin plug and the other a 3pin plug (only 2 pins used). On the 5-pin connector, locations 1 & 2 go to the 3-pin connector (at positions 1 & 3). Location 3 is a brown earth wire and locations 4 & 5 are long green wires. Location 4 green wire goes to fuse 2 in the fuse box and location 5 green wire goes to location 3 on the 7-pin blue connector at the back of the instrument panel (it is the only blue connector there and location 3 is empty).
I attached the control box to the side of the radiator housing in the position it is in manual cars, (I used the control box bolt to earth the brown wire) removed the blanking plug from the side of the radiator, clipped in the sensor and then connected the loom to both the sensor and the control box. The 2 long green wires and their protective sleeve were then fed up the side of the car and through the hole in the bulkhead where the bonnet release goes, getting them into the space behind the instrument panel. Once there I cut the wire to the lamp (the wire from location 5 to location 3 on the 7-pin blue connector) to length and soldered on one of the supplied right-angle connectors which I then pushed into blue location3 (make sure you get the right location as these connectors cannot be removed without destroying them). The remaining green wire (from location 4 to fuse2) was passed through the dashboard (I removed the glove box lid and the carpeted undertray below the glovebox) and down to the fuse box.
I was unable to find any blank space in any of the plugs in the fuse box that connected to fuse 2 and didn’t connect up to anything else so I used a piggy-back fuse in fuse 2 location which fitted and provided the ignition-controlled power I needed. I added a lamp to the empty socket behind the window for the low-level warning icon and now, when I press the check button, the lamp comes on with the rest. With the ignition on, the warning lamp came on as I had drained some coolant from the radiator but as I added more, the lamp went out (actually I didn’t have to add more than about ½ litre for the lamp to go out so it suggests that the coolant loss wouldn’t be great before I got the warning (and STOP) lights coming on.
Why it was never fitted on Autos I don’t know but I feel just a little bit safer now that it’s fitted to ours.
Ian