04 Honda Civic with several electrical problems

We just got my daughter her first car. It’s a 2004 Honda Civic EX. The tachometer doesn’t work, the speedometer doesn’t work in really cold weather, the temperature gauge flipped out once when she used the AC to defrost the windshield, at night the lights get dimmer and brighter and the heat doesn’t work when the car is idling and only works intermittently when the car is moving. When we purchased it all the floor mats were gone as well as the pressboard spare tire cover and mat. I believe it might have been flooded or something, although it wasn’t indicated on the Car Facts report. Our mechanic has spent several hours ruling out things and still hasn’t found the problem (though I don’t have the list of things he’s ruled out). The dealership had replaced the battery before we bought it. Other than that it’s in good shape and runs well, although the pick up is on the slow side.

For the temperature gauge and heat issues, the first thing I’d check is air in the cooling system, although I’d hope your mechanic already considered this possibility. For the dimming lights, I’d get a battery and charging system (alternator) test. I’d also check for a slipping serpentine belt. For the slow pickup (if it’s slower than it should be), one thing to check for is an exhaust restriction, which I bring up because you mentioned possible flooding.

I’m assuming your check-engine light isn’t on, as you didn’t mention this. It wouldn’t hurt to check for any stored codes to be safe.

Speaking of belts, you need to check the manual to see if this car has a timing belt. If so, unless you know for sure that it’s already been replaced, you’d better do that right away (unless the other issues cause you to dump this car now) . Be warned that this isn’t cheap.

CarFax by no means gives a complete history, even though many people think that it does.

I hope it hasn’t been flooded, especially by salt water. If so, things will probably just get worse from here as various parts corrode. It might be a good idea to pull up a section of carpet and see what’s underneath.

For future reference, it’s a very good idea to have a mechanic inspect a car before you purchase it. From the list of issues here, I suspect it wouldn’t have been recommended that you buy this car.

The symptoms that the OP describes are exactly the same as the ones that I experienced with my Volvo.
The cause was bad ground connections.
The problem (for me, and possibly for the OP) is tracking down the bad grounds.

I agree that it is almost definite that the car was in a flood.
Unfortunately the OP has learned the hard way that relying on Carfax is…a risky proposition…as those reports omit as much information as they include, and they are hardly worth the paper that they are printed on.

If the OP’s mechanic is stymied by this problem, it might be a good idea to take the car to an automotive electrical specialist shop. There are not many of them, but they can frequently figure out problems of this nature much faster than the average shop.

Bad ground (the key clue here is the flickering headlights). The primary visible ground is the ground battery cable particularly the end bolted to the chassis (should be clean and tight). On a Honda, the second visible ground is the wire going from the valve cover to the radiator support: it tends to get disconnected whenever work on the top end of the motor is performed and doesn’t always get reconnected.

As a quick check, take a pair of jumper cables and jumper from the ground on the battery to a clean point on the chassis, connect the other from a clean point on the engine to a clean point on the chassis and go for a drive.

As an aside: combined with a professional inspection before buying and talking with the current owner, I use and trust CarFax and Experian Vehicle History Reports.

The symptom of no heat at idle – while it could be other things – is often not enough coolant in the cooling system or a bad thermostat. Those are both fairly inexpensive to check. When dash board gauges start acting up, while one possibility is bad grounds, it could also be the voltage regulator for the gauges is on the fritz, or just a corroded connector.

Like some of the others have already stated, cleaning the ground connections under the hood and under the dash with a small brass wire brush will most likely clear some of the electrical problems. Clean the battery connections and check the alternator output wire for signs of burning due to a bad connection. If you work on that connection remove the negative battery connection first since the wire is hot to the battery.

I am mostly concerned what you say about heating issue. If you have made sure the coolant level is okay this may mean air is getting into the coolant due to a headgasket leak. Hopefully you got a very good deal on this car as it sounds that it might need some expensive repairs in the future.

How many miles?