thetundrawolf

So I had my instrument cluster apart, and I cleaned the faces of the gauges (I had it apart for other reasons) with a rag. Now, I think that I bent the needle or something, because even driving downhill or idling the gauge reads pretty close to the red, where before it never really got past 1/4. (It's reading 2/3 now...)

I read the body electrical in the 1983 manual (I have an 82 PU, 22R) but it doesn't give me any indication as to where the needle should be pointing for what resistance.

Can anyone tell me what resistance makes the needle point a certain way?

I am leaving for a long trip tomorrow, and I'll have major stress if I can't figure this out.

83

You won't run into a ton of people who have had their gauges apart...but hopefully someone can help you. I don't know anything about the resistance...

I would just guess that if you took the cluster out again and took off the cover and looked around, you may very well be able to figure out what's wrong. I definitely screwed some things up when I took my cluster apart (speedometer only working when going in reverse, and just bouncing against 0 when I was driving straight ), and it just took going back in and looking around a bit to figure out how to make it right.

thetundrawolf

Okay, so using my DMM and infrared thermometer, these are the results I get.

356 ohms cold, measured at the sender, the wire disconnected.

250 ohms starting to warm up

145 ohms @ 141 degrees F, measured at the sender, gauge just beginning to move past the cold mark.

100 ohms @154 degrees F, needle now 1/4 of the way between the two inner white marks on the gauge face.

75 ohms @ 168 degrees F, needle now halfway between the two inner white marks on the gauge face.

62 ohms (Might have been an anomaly, or I read it wrong) @ 174 degrees F, needle around 58% between the two inner white marks on the gauge face.

70 ohms @ 179 degrees F, needle at 62% or so between the two inner white marks on the gauge face

53.6 ohms @ 200 degrees F after pulling a heavy load up a steep hill, needle now traveled 80% of the way to the final white mark on the gauge face. Radiator is at 186 degrees F.

71 ohms at 195 degrees F, stopping to idle after pulling the heavy load. Upper radiator hose is at 171 degrees F, lower radiator hose is at 161 degrees F, radiator top is at 185 degrees, needle back to being around 65% of the way to the final white mark on the gauge face.



My question is, at what temperature is the coolant considered to be overheating? At what temperature should the coolant be for the gauge to read in the red?

thetundrawolf

Well, my concern is that I am overheating it, that something has changed. I noticed I was leaking some coolant from a clamp I didn't tighten tight enough on the upper radiator hose. It's possible that my gauge was always reading wrong at around 1/4 of the way between the two inner white marks on the gauge face, and never usually going much past it. And now it's reading right. I don't know :/ But it seems even pulling a heavy load the radiator never gets to 200 degrees, and the area around the sender will just barely hit it. I know that's not the coolant temperature, but right now it's all I have.

83

Ah. I was assuming that the only thing that had changed since the last time you drove it was the cluster.

Other than googling or calling a mechanic or something, I'm not sure what to tell you for what temp is considered in the normal range.

yoterman82

I just changed the tstat in my 82 with a 22r and it calls for a 190deg stat in it so 190-195 I believe was you highest reading then it dropped so it isn't over heating gauge is off or sensor my sensor had a ton of crap all over the end of it so i cleaned it up when it was apart

thetundrawolf

I think I have a 160 or 170 degree one in mine, I don't remember exactly. Wondering if I just shouldn't pop it out. It's an RV and sees heavy use, it's not like it's not an RV some days, and an RV other days. Yeah, I think you're right. Still trying to figure out what resistance puts it in the red on the gauge.

suncomb1

Toyota only shows the following in the FSM: 25 Ohms at terminals A and B on the Water Temperature Gauge and with the ignition on 2-7 volts at Terminals A and B.

Water Tempertature Sensor:

Water Temperature 122 degrees = 154 Ohms
Water Temperature 176 degrees = 52 Ohms
Water Temperature 212 degrees = 27.5 Ohms
Water Temperature 248 degrees = 16 Ohms