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2003 Honda Civic Temp Gauge Drops

2003 HONDA CIVIC
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CURTISMARTELL
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1.7L 2 door Si coupe, 132,000 kms on it. Still having the same problems with the temperature gauge inside the car dopping to the cold mark when i have the blower on high speed. Replaced the temp sensor and the thermostat, both at honda dealers, and still no luck. Honda dealers checked it out and said they don't know what's wrong with it, and told me just to not put the heater on high!! Waste of money. Can someone please help???
Jan 16, 2007 at 6:47 AM
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LOSONE
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Do you know if the engine temp goes down or the gauge reads low?

I ran into this problems a few years ago and I found that the alternator would drop below 12 volts when the heater was placed on high.The heater blower draws a lot of current.

Have a tech place a volt meter acroos the battery and observe the voltage with the car idling and the blower motor on high. If it drops below 13 volts you have an alternator problem. The dash has a voltage regulator that needs 13 volts to operate all the gauges.

Let me know and we can explore this problem further. I need to know the country where the vehicle resides.

Losone
Jan 22, 2007 at 9:58 AM
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CURTISMARTELL
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Hey. Thanks for the reply. The car is in canada. Basically, if i put the blower on high, the car will not heat up, wheter i am driving or running idle in park. And it will blow cool air out of the vents. I have taken it to 2 honda dealers, and the basically both told me not to turn the blower up to high which really made me mad. If i turn on the blower halfway, the car will blow warm air, and the temperature gauge will rise to the normal mid-point level. I can tell you the car's rpm gauge is going weird as well. It is bouncing up and down depending on what level i turn the blower on, or if i turn on the rear defrost. I hope this helps you to help me solve this problem. Thanks.
Jan 22, 2007 at 10:04 AM
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LOSONE
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I must get clarification about "won't warm up." Does this mean inside the car or the engine remains cold?

I spoke at length with a senior Tech at the Honda shop and he gave me some ideas.

The odd idle is interesting.

Let me know Losone
Jan 23, 2007 at 10:19 AM
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CURTISMARTELL
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Well, to the best of my knowledge, the engine remains cold. After it is at normal temp on the temperature gauge, and i turn the blower on full blast, the needle on the gauge will start to drop and the blower will blow out cooler air instead of warm. So i guess that means the engine is cooling off as well.
Jan 23, 2007 at 10:22 AM
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CURTISMARTELL
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I spoke with a friend of mine and he said he ran by a problem like this a few years back, and it had to do with the blower taking too much voltage from the alternator. I don't know if that even makes sense, but i thought i would put it on here and let anyone know if that makes any sense.
Jan 23, 2007 at 10:23 AM
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LOSONE
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I want you to physically feel of the engine radiator and verify IF the engine is cold. All that I have heard I am leaning toward a electrical problem as i first wrote Let me know.
Jan 23, 2007 at 10:35 AM
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CURTISMARTELL
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ok, it is very late this evening, and i will give it a try tomorrow morning, but what part of the car should i be feeling? I apoligize for my ignorance. Should i try the radiator hoses? Or something else? Please help me put it in terms someone stupid like me could understand. Thanks.
Jan 23, 2007 at 10:37 AM
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LOSONE
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When the car is at normal operating temp (center of dial) careully feel the top hose and the top of the radiator. Just a glancing touch will let you know if it is hot. Like toughinh a hot iron. Do the same thing when the symptom occurs. I want to isolate engine from electrical. Losone
Jan 23, 2007 at 10:45 AM
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CURTISMARTELL
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ok, i will try that tomorrow. I will touch the top hose, and the radiator when the temp is normal, and then i will wait until the temp drops and touch them again. I really want to express my thanks on your help on this matter. It is really bothering me quite a bit, and you are being very helpful, and taking your time to try and solve this problem for me. You are a great asset to this website. Much thanks.
Jan 23, 2007 at 10:54 AM
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CURTISMARTELL
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Hey. The hoses are both heated. Also, i was driving the other day and my check engine light came on. I took it to the local mechanic, and he put it on the computer, and said it came up with an error about the TPS sensor. (throttle positioning sensor). Now on Honda's, they are riveted to the throttle body, so before i replace the throttle body at a 600 cost, can this possible be related to my other problem? Also, is there such a thing as a coolant temperature sensor?
Feb 2, 2007 at 7:07 AM
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LOSONE
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There is no connection between a TPS and an electrical dash problem. Yes there is a coolant temperature sensor.

The TPS is an important sensor as it gives the throttle position to the computer which controls fuel flow. $600 in any dollars is too much. The sensor is about $50.00 and the labor about the same. It is no big deal to replace it. Go to a non dealership garage!

losone
Feb 2, 2007 at 8:33 AM
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CURTISMARTELL
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well, it is not 50 bucks, because on Honda's, the TPS is riveted to the throttle body. If you need to replace the sensor, you have to replace the whole throttle body. 600 was the price from the dealer for the throttle body with the sensor attached. And when i hooked it to the computer with the mechanic at the garage, that's the error it was giving me - please help
Feb 2, 2007 at 8:36 AM
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LOSONE
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I have drilled out many TPS's on Hondas and replaced them. 1st check with your local parts house and see if they make a replacement tPS. If not you are stuck with the 600 unless the local wrecking yard has one. The 1.7L is not imported to the US.

E mail me direct if you wish at losone@cableone.net
Feb 2, 2007 at 8:52 AM

Suggested Repair

With the engine at normal temperature, compare the top radiator hose and radiator when the gauge is normal and when it drops. If they stay hot, the engine is not actually cooling and the gauge drop is electrical. Measure battery voltage at idle with the blower on high; a drop below about 13 volts points to a weak alternator or charging problem affecting the gauges. The TPS code is unrelated; check whether the sensor can be replaced separately before buying a throttle body.

Conversation Summary

A 2003 Honda Civic Si in Canada shows a temperature gauge that falls to cold and vents that blow cooler air when the blower is on high, while half speed allows normal warm air and a mid-gauge reading. The thermostat and temperature sensor were already replaced, and dealers had no diagnosis. The owner also reported the tachometer reacting to blower and rear-defroster load, then a TPS code. After checking, the radiator hoses remained hot when the gauge dropped, supporting an electrical or charging issue rather than actual engine cooling. The expert advised a battery voltage test with the blower on high and said the TPS fault is separate and may not require a full throttle body.

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