Originally Posted by gearbox

1. check ECT (engine coolant temp) sensor above thermostat in the engine, that sends the signal to the temp gauge.

2. check the fan sensor which is poking inside the thermostat housing. that tells the fan when to turn on when coolant gets too hot.

3. check the fan relay (not fuses)

4. check the cluster wiring for shorts or loose wires. when the park lights are on, try turning up the dimmer **** (it could be on low).

Originally Posted by gearbox

fan relay is in the under hood fuse box, it says which one in the owner manual. have you tried supplying power directly to the fans to make sure they work?

I will try it tomorrow, wonder why the fans dont come on when i turn the a/c on...a/c dont work by the way..

if you have 01-05 civic, here is how to test the sensors. there is no test procedure in the manual. but what i would do is remove it, then put the tip in various degrees of water. like one cold, one room temp, one hot. measure the resistance in each liquid and you should be getting different resistance readings each time (use multi/ohm meter). if readings are the same, sensor is bad. for the fan sensor, there is no way to really test i dont think, aside from first supplying power directly to the fan. it could also be the relay gone bad or something with the wiring. or it could be it just needs a new fan switch/sensor.

yes i have a 02...
oh so take the sensor out and hook the meter to the sensor?

for the fan, check number 4 and 14 fuses in underDASH fuse box. remove fan relay from underHOOD fusebox and test it. the fan relay is a normally open type A relay. connect power and ground to number 3 and 4 terminals of the relay, then test for continuity between number 1 and 2 terminals. if no continuity, replace relay. when power is disconnected from number 3 and 4 terminals, there should NOT be continuity between 1 and 2 terminals. now go to the fan relay "connector" socket in the under hood fuse box. measure the voltage at the number one terminal with a multimeter. there should be +12v. if not, the fuse box must be replaced. if there is power, get or make a jumper wire and connect the number 1 and 2 socket terminals together. the fan should now come on. if it works, remove the jumper and turn the ignition to ON, without starting the motor. check voltage at number 3 terminal of socket. if no voltage, its a wire issue between the two fuse boxes. if there is 12v, turn car off and reinstall fan relay into the socket. now go find the fan sensor in the thermostat assembly and unplug the connector harness. jump the two terminals together and see if the fan turns on. if it does, you need a new fan switch. if it doesnt, you have a wiring problem going to the switch. to test the fan switch, put it in boiling water and measure continuity between the two terminals of the switch. there should be continuity. in room temp water, there should be no continuity.

Originally Posted by gearbox

17 is the ECT water temp sensor, at the top of the engine near the thermostat. the fan sensor is angled down and is actually inside the thermostat bulb housing, number 16

Originally Posted by tinman

The gauges have a self diagnostic function

check fuse #9 in underhood fuse box and #10 in under dash fuse box.

1. push and hold trip reset button
2. turn the lighting switch on
3. turn the ignition switch ON (do not start engine)
4. within 5 seconds, turn the lighting switch off, then on and off again.
5. within another 5 seconds, release the trip meter button, then push and release the button 4 times repeatedly.

notes: diagnostic mode ends when ignition is switched off or vehicle speed exceeds 1mph.

all gauge needles should make a full sweep from min to max and back again. beeper sounds 5x, indicator lights flash, segment display flashes 5x. pressing the trip meter will restart needle sweep.

Originally Posted by gearbox

ECT is basically a temperature sensitive resistor. depending how hot it gets, it sends different readings to the cluster and also the ecu. are you having any idle or warmup issues? cause thats a sure sign of a bad sensor. you may also want to make sure the gauge wire is not loose or anything by jiggling around the wiring. im not sure how you can test the sensor, i dont know the logic it uses to communicate with gauges. but there is a gauge test mode you can do to make sure the cluster isnt bad. it will sweep all the needles on auto and if the temp gauge still doesnt move, you know the temp gauge is the problem and its time for a new gauge cluster.

Originally Posted by gearbox

depends, i think sometimes the fans will not come on if there is a problem with the compressor circuit. did you do any of the other tests to see if its a fan sensor or wiring? what do you mean the cluster test says error? in the lcd part? thats a serious problem, it means the communication line is faulty. it should be reading 88888.8 if everything is fine. Error code means there is a malfunction between the gauges, the multiplex unit, and the ECM. If there is any failure of the diagnostic tests, the cluster must be replaced. and hopefully that will fix the problems.

Originally Posted by gearbox

ah okay nevermind then. i bet thats the reason. did your coolant gauge stop working when you installed the bypass? it may be related. i think cluster gets its coolant temp reading thru the ecu and multiplex unit, and ecu gets the info from the water temp ect sensor in the block. if it says error, there is def a communication problem and that is prolly why the temp gauge wont work (it moves for the test, but its not receiving data from multiplex unit).

Originally Posted by gearbox

lol wow. a locksmith can prolly make a key and program it yes. not reflash the ecu, only honda dealer can. so basically you want a key that works with the stock ecu? im pretty sure the bypass is causing the problem tho. im surprised you dont have more issues.

Originally Posted by gearbox

wow nice so the temp gauge works now? about the battery, what does voltage read with car off? and yeah the battery light only comes on when alternator is bad. but it might be slightly bad and not producing the full 70amps. ive seen some that still put out 30-40 amps so they technically still work but not enough to power the car and charge the battery. i would just get a test at the auto store. sounds like battery but you should be getting 14v with car running. make sure you have a good connection when youre testing. check the battery with car off, and then try charging it with a slow amp trickle charger. they sell em at auto store for around $50 and its well worth it. charge up the battery to full 12.6v and see if it holds charge.

Originally Posted by gearbox

get a trickle charger like a 1amp and leave it hooked up til the charged light comes on. it takes longer but will not ruin the battery. then wait a few days if you can and see if the voltage drps down from 12.6v. did you get the alternator checked?

Originally Posted by gearbox

yeah their machine should be able to check it on the car so long as battery is charged. kragen will do it too. advance auto has the best setup if you have a store nearby.