What's the Deal With Those FLOOR TEMP Warning Lights in Malaise Era Datsuns?
A couple of recent Junkyard Find Datsuns (the ’78 510 and ’77 280Z) featured mysterious “FLOOR TEMP” idiot lights on their dashes. Floor temp? Why?
The thing that really put the malaise into the Malaise Era was the inability of the automotive industry to meet US federal and– in the case of cars sold in California— state exhaust-emission regulations without crippling the vehicles (whether this inability was due to Naderite anti-progress bomb-throwers infesting the government or corporate mismanagement and the over-reliance on lobbying to fend off emissions regulations is your subject to debate). While Honda’s CVCC engines managed to beat the tailpipe test without the use of the early, incredibly inefficient catalytic converters, just about everybody else had to bolt a super-restrictive and surface-of-sun-temperature cat onto the exhaust. On low, sporty vehicles that didn’t have a good location for the catalytic converter, an overheating cat could set the car’s interior on fire. Nissan’s solution to this was the FLOOR TEMP indicator light, which used a temperature sensor near the catalytic converter to warn the driver to slow the hell down. We can assume that no Datsun drivers actually read the owner’s manual (as a former technical writer, I know that you can’t get anybody to RTFM), and so the FLOOR TEMP light just confused them.
The Italians took a different approach. Fiats, Ferraris, and (I’m pretty sure) Alfa Romeos of the late 1970s got this lovely and equally confusing “SLOW DOWN” idiot light to warn drivers of overheating catalytic converters; at least this light gave the driver some idea of the remedy for the problem. Some Fiats and British Leyland cars got a similarly cryptic (yet technically more accurate) “CATALYST” idiot light. Perhaps a really big idiot light reading “CATALYTIC CONVERTER OVERHEATING — SLOW YOUR ASS DOWN OR PERISH IN FLAMES!” would have been best.
Murilee Martin is the pen name of Phil Greden, a writer who has lived in Minnesota, California, Georgia and (now) Colorado. He has toiled at copywriting, technical writing, junkmail writing, fiction writing and now automotive writing. He has owned many terrible vehicles and some good ones. He spends a great deal of time in self-service junkyards. These days, he writes for publications including Autoweek, Autoblog, Hagerty, The Truth About Cars and Capital One.
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Ford enriched the mixture in their carbs at idle in an attempt to cool down the cat. The 300cu six I had with an electronic carb has a solenoid for this purpose. I didn't think it worked in any case.
I always thought it was running too LEAN that cases the cat to glow. Or the exhaust.