92 Accord Temperature Gauge Problem

I have a 92 Accord LX 4dr with 207k miles on it. The temperature gauge
started acting up recently. When I start the car the gauge immediately
goes to the top and just stays there until a few seconds after I turn
the car off. Then it slowly drops down to the bottom. The antifreeze
level is good and I made sure there are no bubbles in the system by
opening the bleed bolt until the coolant runs steady with no bubbles in
it. In fact if I turn the key to the accessory position the gauge will
max out before the car is even started. The car runs fine otherwise.

Any ideas what the problem might be? Bad gauge or bad sending unit?

Thanks

 

Sounds like a bad gauge.

Unplug the sender unit, which is a one-wire thingy at the rear of the
header (opposite end from the timing belt). If the gauge still acts the
same, the gauge is bad. If the gauge then does nothing, then the sender is
bad.

 

Tegger,

Did it and the gauge did nothing so it must be a bad sending unit.

Will try to pick one up tomorrow. I'm guessing the dealer will have to
order one though.

Thanks for the help.

 

If you order it early enough in the morning, they may be able to get it
same-day.

The danger here is the short in the sender unit may have caused damage to
the gauge, so if the temperature gauge still acts oddly, you may have to
get another one. You can find a cheap replacement at a wrecking yard.

 

Sorry, meant to type "SENDER", not "gauge". Just noticed this now.

 

The dealer didn't have one in stock so they had to order one. They said
it would be a day or two. I left the unit unplugged. Hopefully the
gauge is still ok. I don't really want to have to pull the instrument
cluster. If it is I'll start calling junk yards.

 

You're probably OK. It's probably more likely the sender has just lost some
of its resistance rather than actually shorted. The loss of resistance can
be detected with a multimeter (S/B 142 ohms at cold, approx 35 at full op-
temp).

Some clarification: the "sender" unit isn't really a "sender", but a
variable grounder. Current goes through the gauge and then to ground
through the sender. The sender has variable resistance that decreases with
increased coolant temperature. Decreased resistance means more current
flowing to ground and a higher gauge needle reading.

 

Thanks for the clarification. I checked the resistance and it reads as
0 so I'm guessing that means it's dead. Went to pick up the part and it
was the wrong one. They ordered the sensor that goes in the thermostat
housing so I'll have to wait a couple more days.

 

Zero ohms? Ugh. You may actually have a dead-short there. Watch that gauge
once the new sender is installed.

 

Yep, 0. Before I unhooked it the guage was still going up and down.
I'm really hoping that it's ok. When I replace the sender I'm going to
change the antifreeze. Do you recommend going with Honda antifreeze?

 

Absolutely. Do not neglect to pull the block drain as well as the rad
drain, and flush the works with a garden hose.

** Remember to turn the heater to full-hot first.**

 

The thermo unit (what the package says) is in and the gauge is working
good. Whew!

Will do the coolant change this weekend. No time today, beggars night
and all that. I had the dealer install an engine block heater and I
believe it is located in the block drain hole. Do you happen to know if
I need to put any kind of thread sealant on the heater before I put it
back in.

 

@newsfarm.iad.highwinds-media.com:

Success is always nice.

I use one turn of Teflon plumber's tape, wrapped such that it will not
unwind when I screw the drain bolt back in.

 

That'll work. I always have some teflon tape laying around.

Thanks again for the advice.