I am having a couple issues with a 91 honda civic si I just bought, my main concern is my temp gauge is not working. I snapped a couple pictures in hopes they may help. My radio is also not working correctly, I have all wires hooked up properly, and it stays on w/ car is off. I believe my ign wires may have been tampered with or something? not sure!

one picture is the back of my cluster, it looks to me like a plug is missing. One of the pictures is of the left side of the head, right beneath the valve cover (of what I believe to be the thermostat or oil psi sensor.) There is a picture of a cut wire that I found underneath the dash (not sure what it is). The other picture speaks for its self! I hope you can distinguish the pictures from my comments lol.

 

Try to take some pics that are less fuzzy! That will help determine if foul play is at hand... Mr. Watson, we have some investigating to do.

 

There are two temperature sensors screwed into the head below the distributor. The one near the front of the car tells the ECU whether the engine is warmed up. I think that is the one in your picture, it should have a two wire plug on it. The one near the back of the car has a single pin plug and it operates the gauge on the dash. Most likely that one is not hooked up either.

In the second picture, someone has tapped into one of the wires of the car, and the red wire would go to something aftermarket. Then it appears whatever it was was removed. You can just remove the scotchlock connector and extra red wire, then tape up the wire in the harness.

I don't recognize what the third picture is showing.

The radio is powered by a white wire with blue stripe that is live all the time, and a white wire with green stripe that is only live when the key is on. These wires should be patched through to the yellow and red wires respectively of a standard aftermarket radio. The white and green wire is switched through a relay mounted on the bracket near and below the radio. If the white and green wire remains live with the key off, check the relay.

 

Check the plugs on the back of the block near the oil filter. These cars are reaching 20 years old and the wires back there become very brittle. I know i went to plug mine in and it just crumbled. My guess is it either slipped of or broke.

The extra plug on the back of your cluster I believe is for cruise control. If you don't have it don't worry about it. Im not 100% sure but pretty sure.


The Yellow with red stripe wire that someone tapped into is your 12v ignition wire. This would wire to the Red on on your stereo. This is only on when the Key is turned on.

MK is right about the white wire with blue stripe, but it can also be a white wire with a yellow stripe. This is your 12+ or memory wire that should go to the yellow of your stereo harness.

My guess is that someone tapped into the ignition wire for either an amp or just hacked the stereo wiring.

As for your engine bay picture. It really doesn't show anything. I can vaguely make out a Black with yellow stripe wire which would be your ignition wire. Really can't tell where it goes or what it does.

 

Thank you for the comments, I have pretty much figured out most of my problems. Although I am not really sure what wires your talking about near the oil filter Hailchristian, are you talking about what mk378 was talking about when he said "...The one near the back of the car has a single pin plug and it operates the gauge on the dash. Most likely that one is not hooked up either".

I am going to check that out, where exactly is the sending unit located? also one thing I was wondering, do you think its most likely a faulty wire connection that is causing my temp gauge not to work, and not a broken thermostat?

 

I was actually mistaken.

There are 3 coolant temperature sensors.




The one that controls the temp gauge is the green one. Make sure that is plugged in.

The red one is the one that sends information to your ECU. If it isn't plugged in, your car will have a check engine light.

The one on the back of the block next to the oil filter (blue in the picture), makes sure the fan kicks on.

Is your coolant gauge responding at all? A faulty thermostat would result in in overheating or an engine not warming up.

Hope this clears things up.

Hope this clears things up.

 

Looks to me like your cluster is an automatic one from a Sedan?
Take a picture showing the gauge faces and we can confirm.

 

The green sensor in Hailchristian's picture is the one for the gauge. Take the wire off and ground it to the engine. When you turn the key on, the gauge should go up towards hot (turn the key off before it can jam there).

If the thermostat is bad you won't get much hot air from the heater. The gauge may come off the peg at cold only when driving at higher speeds and / or up hills. That needs to be fixed because you will get lower gas mileage and lots of crud in the oil driving with an engine that doesn't warm up.