6

Dashboard Mystery Light

The light can be switched on or off by operation of the stem on the right of the steering wheel, the same control that operates the windshield wipers.

I can't detect any difference whether it is on or off.

  • It will be in the owners manual if you have one. Kind of looks like a throttle body, but can't say I've ever seen anything like it. – raydowe Sep 21 '17 at 13:46
  • @raydowe throttle body, good idea, so could it be carb heat or manifold heat? – Solar Mike Sep 21 '17 at 14:23
  • Now I'm really interested in what this symbol is. Does the switch that operates it have any markings on it? If you figure it out, please let us know. – JPhi1618 Sep 21 '17 at 14:50
5

That light indicates the Exhaust Brake feature is active and will work to slow the vehicle when your foot is taken off the accelerator. The picture is meant to be a throttle plate in the closed position (the horizontal line with the dot in the middle) and air being stopped by the plate (the vertical lines).

Here is a question on another site that describes it:

It has 2 uses. In the winter you flip a switch and the hot exhaust goes back through the engine to warm it up faster. When driving down the road you take your foot off the throttle and a switch kicks in to redirect the exhaust to help slow the truck down. Saves on the brakes if you not a speedster.

https://www.lawnsite.com/threads/bought-an-isuzu-npr-now-i-have-questions.224065/

And this is a product image of the turn signal switch for that truck from Amazon whose description says:

List Price Is Over Than $300.00 It Has The Exhaust Brake Switch For Diesel Engine.

enter image description here

  • Quoting the actual info from that thread you linked (otherwise this is almost a link-only answer): "It has 2 uses. In the winter you flip a switch and the hot exhaust goes back through the engine to warm it up faster. When driving down the road you take your foot off the throttle and a switch kicks in to redirect the exhaust to help slow the truck down. Saves on the brakes if you not a speedster." – Peter Cordes Sep 21 '17 at 15:18
  • @PeterCordes, thanks for pointing out that quote. I answered what the light was and what the picture was supposed to be, but that quote also helps explain the feature. – JPhi1618 Sep 21 '17 at 15:32
  • Yeah, your detective work was already enough to go look up the feature by its name, nice find. But it only felt like half an answer to give the name but not describe what it does, because that's totally non-obvious to curious non-truck-experts. – Peter Cordes Sep 21 '17 at 15:35

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