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OAT indicator reads low

Posted: Wed Feb 02, 2011 3:24 pm
by kolmstead
This one is petty, but a little annoying. The LEAF has an outside air temperature sensor located up front. Mine reads at least ten degrees Fahrenheit lower than actual outside temperature, compared with numerous thermometers and a calibrated weather station at work. For several days I was wondering why it felt pretty nice out in the morning despite the 25 F reading in the car. Eventually I figured out that the car was wrong. The error seems to diminish as temps go up; at 70 degrees, it's probably close to nil.

Apparently Nissan knows about this one; there's a disclaimer in the owner's manual that the car's indicator will probably not agree with other sources. If that's the case, why bother? And what's this low OAT warning at 38 degrees about? Is something bad supposed to happen at that temp?

Just my personal bias as an instrumentation guy. Better to display no data than incorrect data...

-Karl

Re: OAT indicator reads low

Posted: Wed Feb 02, 2011 4:09 pm
by GeekEV
At 37/38 and below you're much more likely to encounter black ice on the road if there's any moisture at all. It's warning you to be careful.

Re: OAT indicator reads low

Posted: Wed Feb 02, 2011 9:38 pm
by Rat
My Volvo lights up a little snowflake on the dash somewhere around there, maybe at 35 or so. Same reason, I'm sure.

Re: OAT indicator reads low

Posted: Wed Feb 02, 2011 9:51 pm
by EVDRIVER
Karl,

I could not agree more. My Toyota truck and other brand cars I have owned have had decent accuracy on the temp sensors and the clocks were always perfect. I have never been a Nissan owner because I always felt there cars were not up to par with the quality of other brands at some levels although they have been improving. Making an accurate temp sensor and clock is as simple as it gets, if they can'e get it within + - 2 degrees F then it does not belong there. If their clocks really are off minutes each week they need to fire some engineers or take them out. A high tech car should not have such gross errors like this. Even the most basic temp sensors have calibration adjustments, what's the point of the fancy telematics if you can't fix these issues. Makes me wonder about their pack sensors. Anyone checked the speedometer?

Re: OAT indicator reads low

Posted: Wed Feb 02, 2011 11:37 pm
by LEAFfan
EVDRIVER wrote:Anyone checked the speedometer?
You must have missed an earlier post from Skywagon. He said it is only off by +1 according to his GPS. I have yet to see a speedo be low. Most I've seen are off by +4-5 mph. My Honda Civic was off by +4 until I changed the tire size. Now it's only +1 all the way up to 75mph.

Re: OAT indicator reads low

Posted: Wed Feb 02, 2011 11:54 pm
by garygid
Speedometer is required by law to read high, I believe.

Re: OAT indicator reads low

Posted: Thu Feb 03, 2011 12:19 am
by LEAFfan
garygid wrote:Speedometer is required by law to read high, I believe.
Since when? When I had VW Rabbits (77-84) with VDO gauges, the speedo was exactly 60 at 60mph. I've never seen more accurate gauges since so that's why I'm wondering if and when that became a law to be high.

Re: OAT indicator reads low

Posted: Thu Feb 03, 2011 2:31 am
by garygid
I thought (do not know the law or ruling) that the US requires the manufacturer-displayed speed readings to be a percent high, and Europe requires more, like perhaps 2% high. But, I could be wrong.

Note that many/most/all/some built-in GPS Nav systems do not display speed at all.

However, most hand-held GPS Nav devices do.

Re: OAT indicator reads low

Posted: Thu Feb 03, 2011 8:21 am
by turbo2ltr
My 01 Grand Cherokee matches my GPS exactly. The OAT reads a little weird sometimes though.

Re: OAT indicator reads low

Posted: Fri Feb 04, 2011 8:44 pm
by BnBinSD
Regarding the accuracy of any speedometer, be aware that this will vary with the age of your tires and their wear impacting the overall diameter. The best source of tire information I've found online is at TireRack. I've found many of my assumptions about tires proven incorrect using their research, which they actually perform.

Try the link below, then click the Speedometer Accuracy link. There's a chart there you can use to verify your speedometer.

http://www.tirerack.com/tires/tiretech/tiretech.jsp

[quote="garygid"]I thought (do not know the law or ruling) that the US requires the manufacturer-displayed speed readings to be a percent high, and Europe requires more, like perhaps 2% high. But, I could be wrong.