Heat light stays on

McOz · Postby **McOz** » Mon Oct 31, 2011 4:54 pm

The heat light on my imported NA6 is lit up and won't go home. This occurred over the weekend during a sprint competition run - I lost power, and ambled it back to the parking lot. A fellow racer kindly diagnosed the issue - a spark plug lead had disconnected at the coil end.

Any suggestions on:
- what causes the heat light to come on in the first place?
- what could be causing the heat light to stay on?
- any possible fixes?

I don't want to just pull the plug on the sensor without knowing if something actually requires attention. I also want to know *why* this occurred.

spikes · Postby **spikes** » Mon Oct 31, 2011 6:39 pm

Unplug the wire from the cat, not quite a fix but my light does the same, stays on always. unplugged cable and it turns off. My car came like this from the PO so I have no idea what's he done but there doesn't seem to be any troubles

sailaholic · Postby **sailaholic** » Mon Oct 31, 2011 6:47 pm

I think its a warning that the cat is rooted. Cats need to be heated to work so I believe the warning was a Japan requirement to say it was still preheating or worn out.

Likely the disconnectrd plug lead put enough fuel through it to finish it off.

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McOz · Postby **McOz** » Mon Oct 31, 2011 7:07 pm

sailaholic wrote:... Likely the disconnectrd plug lead put enough fuel through it to finish it off.

Let me make sure I understand...with one cylinder not firing, that cylinders' fuel was being expelled on the exhaust stroke, through the exhaust manifold to the cat. The unburned fuel was enough to root the ceramic insides of the catalytic converter. Now, it's not able to hold enough exhaust gas or the gas passes too quickly through the cat to get hot enough to do it's job - heating the exhaust gages to get rid of left over nasties?

Does that sound even slightly accurate?

Postby **NitroDann** » Mon Oct 31, 2011 7:14 pm

The cats job is to burn unburned hydrocarbons.

Those gases that arent fully combusted.

When you run straight fuel and air into it it burns it like crazy, so it melts into itself and dies. Now its totalled and probably is boht blocking your exhaust, and not working at all.

Dann

McOz · Postby **McOz** » Mon Oct 31, 2011 8:32 pm

Awesome, got it. Thanks NitroDan

geofiz · Postby **geofiz** » Mon Oct 31, 2011 11:17 pm

Sounds like time for a new cat. I can put you in touch with a good exhaust guy who is local for us. Did my exhaust system for a good price..

McOz · Postby **McOz** » Tue Nov 01, 2011 12:02 am

Definitely keen to explore that option, would love to get a full cat and back exhaust. Will give you a buzz.

Sailor · Postby **Sailor** » Tue Nov 01, 2011 12:44 pm

Don't know the NA6 at all but I'd suggest that it's not unusual for a fouled O2 sensor to trigger a fault light.
I'd be pulling it/them and cleaning with one of the available cleaners after testing it/them

93_Clubman · Postby **93_Clubman** » Tue Nov 01, 2011 2:13 pm

Some info on the Eunos Roadster cat sensor:
http://www.quithel.co.uk/zz_Eunos_v_MX5.htm
http://forum.miata.net/vb/archive/index ... 04491.html
http://realbig.com/miata/1999-05/2427.html

McOz · Postby **McOz** » Fri Nov 04, 2011 12:08 am

Replaced cat, light still on - any suggestions?

hks_kansei · Postby **hks_kansei** » Fri Nov 04, 2011 8:42 am

Seeing as how it's a warning for something quite silly (who really cares if the cat is warm yet in nomral life)

you could simply take out the bulb so it can't light up?

Charlie Brown · Postby **Charlie Brown** » Fri Nov 04, 2011 9:05 am

hks_kansei wrote:Seeing as how it's a warning for something quite silly (who really cares if the cat is warm yet in nomral life)

you could simply take out the bulb so it can't light up?

Putting your head in the sand doesn't solve the problem.

Read the articles posted by 93_Clubman and see if anything matched.

With the NC, to reset the fault problems you disconnect the battery and put your foot on the brake (ignition turned on) for 30 seconds to drain all power from the computer then reconnect. I dont know if that will work with an NA but may be worth a try.

McOz · Postby **McOz** » Fri Nov 04, 2011 10:45 am

I have:
- read the articles linked above (no resolution fit)
- disconnected the battery to clear any codes

I'd rather fix it than pull the globe / sensor as it's there for a reason. Maybe the sensor has malfunctioned?

93_Clubman · Postby **93_Clubman** » Fri Nov 04, 2011 6:00 pm

McOz wrote:Maybe the sensor has malfunctioned?

So you've refitted the old sensor to the new CAT? Old sensor is also probably unserviceable - maybe try bridging the sensor wires to see if that turns out the light.