Fuel Light

[trdmkii]

Hey does anyones fuel light ever come on, i've never had it come on in either my 84 or 85, now just the other day in my 85 i was bored so i replaaced the bulb and still nothing when i ran the tank down pretty low?, could it be a problem with the sending unit or the circuit board?

[Sparky]

I can vouch that they do come on if you run the car low enough. In mine, it comes on somewhere pretty near E (I've termed it the "your about to run out of gas you idioit" light).

Just FYI

[trdmkii]

well in my 84 i've ran it empty and it never came on, now in my 85 my fuel gauge is off so i'm always afraid of running it below e...lol so i dunno, who knows its not that important to me

[Sparky]

Personally, I depend just as much on the trip odometer as the gas guage; I know when I should be running out of gas, regardless of what it says (though it hasn't been wrong, yet)

[Dave A.]

Pages BE-28 and BE-29 in the 85 TSRM show you how to check the sending unit. An easier way is to check for continuity between terminals 1 and 3 on the 3-prong connector of the sending unit with an ohmeter set on approx. 200 ohm scale. If you don't get a resistance reading then the thermistor is open and you'll need to find another sending unit. Lots of used ones in the j-yards around here.

[Black Dawg]

My '81 the light comes on with about 1 gallon left in the tank.....time to get gas!

[CJSREDPRA]

Actually, the low fuel light in the Redpra stopped working about 9 years ago... Light came on for a brief second & very faint.... Has not come on since then. One of these days when I have the dash out, I need to try replacing the bulb. And I know my sending unit works correctly.....

Then again, right now I have some other issues going on w/ the Redpra.. That came up last night..... Let's just say that the car will be sitting for approx a month.... You'll have to look around for the posting..

[supra_toy]

I remember relying on that little light in one of my old supras one day it diden't come on and I ran out of gas thought I broke it!

will

[NKNVNUNL]

my 85P works without fail - half way between E and the 1/4 mark. this is a little off subject but my old 81 corolla fuel light would start glowing at 1/4 tank and get brighter as it approached E, I thought that was a neat feature since at age 18 we can be hard headed.

[Dave A.]

The low fuel light should normally vary in brightness and get brighter as the fuel level in the tank gets lower. The little chrome plated, bullet shaped capsule on the fuel sending unit is what controls the low fuel light. Inside the capsule is a thermistor that varies resistance to ground in the low fuel light circuit. The thermistor stays cool when submerged in fuel (high resistance, no light) and becomes warm (low resistance, light On) when the fuel level drops below the level of the capsule. The sloshing action of the fuel against the thermistor when the tank gets low is what causes the low fuel light to vary in brightness until the level falls below the capsule and then the light stays on at full brightness. 8)

[CarFreek]

On my 85 the light comes on w 12 Gallons gone almost like clockwork-This leaves me 4 Gallons for reserve-Ive pushed her all the way to 15.5 before-drove 75 miles on light-Like Dave says it gets brighter when its all the way empty-Wonder why so much variance on senders?-My 82 left me w/ about 1.5 Gallons when lite lit-Mike P

[Hosam]

Mine comes on as soon as I've consumed 40-45 litres. It doesn't change brightness though. How come? I have a digital gage. Does that make a diff?

[Digilog]

Mines the exact same and I have the Knight Rider dash as well.


Carl

[Dave A.]

The digital dash cars may use a switch on the fuel gauge sender instead of a thermistor, but I don't know for sure. This may be why the TSRM shows a switch in the electrical diagram instead of a thermistor.