1995 Honda Civic EX 4 Door Automatic

Every morning before I head to work and the temp is below cold as it should be. I put the key to the II position and the temp jumps to 25%. I crank the car and it starts just fine but still stays in the 25% position. I drive for approx. 5 minutes and it reads normal temp (a little under 50%).

When I unplug the temp sensor (one wire) from under the distributor it drops below cold and reads the same temp (48%) when I put it back in.

Upper and lower radiator hoses get hot after normal operating temps so I am assuming the thermostat is okay.

Just found out the radiator fan does not kick on. Jumping the plug so the fan is always on untill I figure out what it could be.

 

The sensor for your gauge cluster is a one-pin plug under the distributor. Unplug it. Does the needle still go to ~25% on cold start?

 

What is the outside air temperature when you start your car in the morning?

 

Are you suggesting the OP lives on Mercury?

 

I would bet these have the same issues as my 98 lx, temp gauge was crazy, would show the engine was overheated within a minute, but if you popped the hood, you could put your hand on the engine, it wasnt the sensor, as I changed it, I did note that none of the aftermarket senders matched Hondas spec, not even close, How long have you owned the car? it's possible someone installed the wrong sender. The only thing I could possibly figure out, was the wiring diagram for the cluster showed a voltage regular built into the circuit board. If it was failing it could cause erratic gauge readings, I never did figure it out as the transmission failed, and I ended up selling the POS. Check your sender against spec with an ohmmeter and if it's good, you might want to swap out the cluster

 

Yeah, for it to be around 25% at start-up, the engine would have to have an ambient temperature of something like 150*F. Getting the block to that temperature without turning it on would take...well, maybe not Mercury, but at least Venus

 

they've been hitting 117 in parts of Cali, friend says it's hell on earth

 

117 < 150.

 

I don't know what 25% is in regards to temperature but I thought the halfway mark was around 200.

100 degrees doesn't seem too difficult to achieve on a hot Phoenix day.

 

The halfway mark is something around 200, but it isn't linear - the bottom mark isn't 0. Realistically, the bottom mark is more like 100.

 

You guys are saying OP needs one of these?
http://s1372.photobucket.com/user/fa...80bf2.jpg.html
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I would guess its a harness problem.

 

Also could be a bad wire or temp gauge.

 

Maybe he can do that trick you guys always do to diagnose these sorta things.

take the voltage at the sensor side of the wire and the dash harness side to see if things are short circuiting. Its something along those lines. I hate doing electro al diagnoses personally, I just wanted to contribute because I had the sensor laying around lol

 

When my Civic engines are fully warmed up, the cluster temp gauge reads approximately 1/3 of the way to Hot, and the engine temp is about 196F.

 

Sensor probably fudged, unplug sensor and see if it still gauge still shows it being warmed.

 

Why not suggest how to do it?

 

I hate diagnosing electrical problems I dont know how yo do it right. Plus I have no idea what any of the values should actually be or where to properly check the electrical value

 

Unplugging the sending unit to see whether the temp gauge needle now stays at Cold is the place to start with this problem, as NotARacist pointed out already.

 

I think he said that he did that, "unplugged the 1 pin sensor under the distributor and it says cold".

that rules out the rest of the system and points to the sensor I guess? These lil guys suck

 

You are correct. I missed that info in the first post.

The sensor is indeed the problem.

 

make sure you get a OEM one, I have never been able to find one that has the correct ohm range aftermarket, I tried every auto parts store there was, every sender read out of factory specs

 

And be careful with the sucker! They're pretty darn fragile.

 

Your civic must have a problem then because the gauge in my Corsica has numbers on it and the halfway mark reads 210.

 

It's just differences between the scales of the gauges.

 

Also, Chevy != Honda.