Temperature Warning Device – (TWD)
The TWD is a simple & inexpensive device employing a dash-mounted LED as early warning of potential engine overheat. I say, ‘potential’ overheat, as the engine can operate quite normally in the 83 >104 degree range. Whilst most driving conditions will produce an operating temp around 83 > 93 degrees, high ambient air temperatures, low road speed & air-conditioning may contribute to operation above 93 degrees. Subsequent loss of coolant at high temps or failure of the thermo-fan may cause a severe overheat situation to develop. The OEM 3–stage temperature gauge appears to start moving up from ‘normal’ around 105+ degrees. If this occurs during highway driving, by the time one notices any change, it is often too late and engine damage may follow.
The TWD takes readings from the Temp Sensor ECU input & the LED can be mounted easily in the dash, almost in direct line-of-sight.
The TWD should be adjusted to trigger ON @ 95 degrees. This setting appears suitable for Australian Summer conditions. (Settable range is approx. 90 > 105 without circuit modification). Coming ON @ 95 degrees provides a visual early warning, and if one were driving on the highway at the time, would almost certainly suggest a problem! Around town, 95 may be registered many minutes after engine is stopped, as coolant absorbs latent engine heat. (Tip: If LED coming ON whilst stuck in traffic, reduce engine load - turn a/c off, shift to Neutral etc.) The TWD LED turns on momentarily, key in ACC position, as an indicator that circuit is functioning. NOTE: TWD's supplied ready-built with 'blinking' LED's (requires modification to circuit) & calibrated to 95 degrees, will turn ON/OFF within 1degree of change. Construction Total cost of components is around $15. A competent DIY enthusiast with modest soldering skills can easily build the TWD. Installation is not difficult, although familiarity with ECU wiring, and multi-meter testing does help.
Miscellaneous: mounting box,
wire, solder - as req'd. [Note: I used a green LED, far brighter than say red - ensure correct mounting for max. visibilty.]
Pic of my ‘roughie’ prototype:
Installation a. Disconnect vehicle’s battery. Expose ECU & remove retaining screws to gain access to the loom & connector. Remove connector cover carefully & locate pins #28 (Yellow with green stripe) & #30 (Black) as in diagram below. CLICK diagram to view picture.
b. Trace the wires (away from the connector) into the loom for about 100 > 150mm to make them easier to work on. Carefully remove 3 > 5mm insulation from each of the 2 wires (Y/g & B) without cutting the wires. Connect suitable length of wiring to each exposed wire & insulate the joins. Tip: leave ECU & loom exposed until all testing/calibration is completed.
Calibration [NB: all pre-built TWD's are calibrated for 95deg on.] Calibration is done by adjusting trimpot (R2) whilst observing engine temperature. This is simplified by using a ConZult type interface: Nissan DataScan software & BlaZt interface cables available here. An alternative means of calibration is by attaching a multi-meter to the ECU output wires (28 & 30) & measuring the voltage vDC. ECU output - TWD calibration table - approximate values
Written by 'K-zed' - www.aus300zx.com Credits: ZCarJase www.nz300zx.org & Zed4Life (AUS) |
