I've recently retrieved a 91 CRX Si from out of state, and about 2 hours into my 7 hour drive home over night, I noticed the headlights and dash lights occasionally dimming. I immediately though 'alternator', but I was able to keep going for a couple more hours with only these intermittent dimming issues. Eventually, the battery light started flashing, and I pulled off and got a room for the night.

The next morning the car cranked right up, I let it run for about an hour, and then took it to a local Firestone with no issues or warning lights. They ran a charging system and battery check, and all they could determine is that when the high beams are turned on, the voltage dipped to around 12v. Everything else seemed normal and they sent me on my way, advising not to use the high beams, as there could be a short or something there.

Well, almost as soon as I'm back on the interstate, the battery light begins flashing again, but only occasionally. It has never come on and stayed on, and is usually not on. I'm thinking there might be a bad ground somewhere, but besides the main battery and engine grounds which seem fine, I have no idea where to start.

I should add, as far as I can tell, this car is very mildly modified (intake, headers/exhaust, upgraded stereo head unit) and has relatively low miles (78,000) on the original motor. The mechanic at Firestone did mention he thinks the previous owner "jumped" some wiring for the fan in front on the headers to make the car run cooler, which it does run extremely and unusually cool according to the temp gauge (at idle, temp gauge reads normal, just under half, but at highway speed the temp goes all the way down to 'C'). This may be related or not, I'm not sure but thought worth mentioning.

Sorry for the long read, any advice is greatly appreciated.

 

These old Civics are notorious for having bad grounding. Add that to age of the cabling, and you get a recipe for dim headlights. I'll paste something from Civic 4G for you.

How to do the BIG 3 upgrade

In the car audio community the Big 3 is one of the most important mods you have to do to your car to improve the electrical system of your car and maintain good power to your audio system. Although this mod is more related and useful to cars with audio systems considering the 4g is in her twenties and most of the wires on the car people leave them stock, doing this upgrade can be beneficial.

In stock form our alt supply a crappy 70 amps, enough for the stock electrical accessories, too weak if you add aftermarket stuff like amps, computers, dc/ac converters, lightning kits, etc. And the amp rating is in stock form, as time passes and with older alternators the output is even lower (the car audio community always hates hondas for this). It's common for people to see their lights dimming at night when amps hit hard or when turning on some additional accessory. Adding a second battery, a capacitor or replacing the alternator for a higher output one can solve this, but still the wires in the "big 3" are the weakest link.
But this is not only for car audio or accessories, as you can see on the site is common for people to have problems starting their cars, erratic idle, low power and other problems that can't seem to be resolved with tune-ups or replacing parts. While upgrading the big 3 is not guaranteed to solve this problems it may be a way to improve them. The following procedure was gathered from several car audio websites, the most important and valuable being 12volt.com (for the audio and electronics enthusiast that place has loads of info).

NOTE: Upgrading the big 3 is not the same as putting ground kits, replacing all your grounds or unifying them. The upgrade is similar but the scope is different.

What is the big 3 upgrade?

The purpose of this upgrade is to improve the capacity of three wires:

1. Battery negative to chassis (gnd).
2. Engine/tranny ground to chassis.
3. Alternator positive to battery positive.

Some people leave the stock wire and simply add the new wires around or over the existing ones. Current always goes the path of less resistance so the stock wires in that situation will be useless. It is then recommended that the stock wires should be eliminated (less clutter and easier to work with).

Tools and stuff needed:

- High strand power cable.
Low strand cable is less flexible and solid core wire is not recommended for cars, it can break.
The length of the cable you get should be enough to cover the 3 positions you can measure it to the exact point or use the stock ones as reference for length.
Gauge of the wire: it depends on your application and plans. If you have or will have an audio setup in your car match the gauge of the wires to the power needs of your car. The cable has to be equal or BIGGER than the power cable of your amps, the alternator wire and the stock wires. The smallest gauge recommended for this upgrade is 4 awg, 2 awg (or bigger) is recommended. There are online charts and calculators that can help you choose the minimum size of the cable according to the amps. If you don't have an audio setup simply use wires bigger than stock ones.
- Ring terminals.Try to get copper ones, not "gold plated". They should fit the cable you selected.
- Soldering iron and core to solder the terminals to the cable.
- Heat shrinking tube for covering the soldered connection, it should fit over the cable-ring terminal end. Don't use tape
- Something to heat it.
- A blade or crimping tool to strip wires
- Wire cutter, pliers, cable ties, wrenches, screwdrivers, new bolts, etc.

Procedure:

1. A cooled engine is better to work with in this. Disconnect the battery and other charged stuff you may have (2nd battery, capacitors). Remove the battery and the tray. Identify the cables to be replaced:
Battery negative to chassis: it goes from the battery negative terminal to a bolt below the battery tray.

Engine/tranny ground to chassis: the engine ground wire goes from the valve cover to a bolt near the right side radiator support bracket (standing in front of the car). In this procedure we are upgrading only the engine ground, however, the tranny ground can be also upgraded if you have enough power cable and terminals (and it's recommended). It goes from a bracket over the tranny to the same point where the battery negative cable is connected. It's a flat braided cable, usually corroded.

Alternator positive to battery positive: it goes from the alternator (a single wire over it), throught the harness and into the main fuse box. It is fused (#31 60A) then the other side goes to the battery. You can go two ways: use one wire from the alt to the fuse box then another from the fuse box to the battery so you use the stock fuse. Or get an online fuse holder with a 60A fuse and you can eliminate the connection to the box (still two wires are needed).

2. After measuring up the wires (leave some slack on them so they can move), cut them and strip the ends so they fit inside the ring terminals. Again measure them so they are not too tight between the points of connection.

3. Insert one end on the ring terminal, crimp the connector to hold the wire (not too strong or it can break strands). Get the soldering iron and solder the wire.

4. If the shrink tubing doesn't fit over the ring terminal then now is the time to insert two cut pieces before you solder the other end ring terminal. It should cover the ring terminal and soldered wire plus 1 cm over the cable insulation. Use a heat gun or something like to heat the tubing and fit it.
Do the same to the other wires, if using a online fuse holder for the alt to bat cable then secure the cable on it as the fuse holder allows.

5. Battery neg to chassis: remove the stock battery negative wire and its terminal. If the grounding point in the chassis is very corroded or in bad form you may decide on making a new point or sand it down, either way be sure the metal surface is in good condition. Attach the terminal to the other end.
Engine gnd to chassis: remove the stock one and place the new one using the same bolts. You may also choose another location on the chassis to mount it.
Alt pos to bat pos: this could be the hardest to change since the stock wire is inside wire loom with the harness behind the block. If you decide on not remove all the wire loom and mess with it then simply disconnect the stock wire over the alt (10mm nut), attach the new wire with its ring terminal and then work from there.If you decided to eliminate the stock fuse and use and online fuse holder remember to place it more close to the battery than the alt and away from heat sources. If you decide to route it through the stock fuse box then connect it to the terminal in the box (if the wire gauge is too big it will be a tight fit) and another wire to the other terminal that goes to the battery. Don't connect it to the battery yet.

6. If you are changing the tranny ground then do it now. Check that all the connections you made are fine, no wires should be near heat sources or too tight between the points. It's a good idea to check the connections with a multimeter that reads resistance. Place one end on the battery negative terminal new wire, the other side to ground. The reading should be less than one. Also check the wire end that goes to the alternator and the other side that goes to the battery. Again if the reading is not less than one and is high then something is bad with the connections or wires, check again.

7. If everything is fine put the battery again in the car, connect the battery positive wire first, then the negative. Start the car and see if there's smoke or any problem with the wires. If you have a voltmeter hooked to the car check the voltage and compare it to previous readings.

 

I have found in our 2 ef's that the sockets on the tail lights corrode. I know that I have a slight leak, but until the weather gets a little warmer, I am not prepared to repair said leak. Anyway, that being said, when the sockets corrode, this described issue has happened to me and found that when I have cleaned the sockets, the problem is resolved until the next time. I use a fitting brush for cleaning copper pipe fittings, this can be found at any hardware store. Good luck.
Regards
Dave

 

a jumped fan shouldnt cause your car to run that cool, but a bad thermostat will.

 

After reading this I did find some mild corrosion in a couple of the rear sockets and cleaned it out with the wire brush as you described, but my problem still exists.

Thanks for the tip though!

 

I have purchased a new thermostat and will install tomorrow!

 

if they wired the fan to always run, then it probably has a bad thermo switch.
Replace that, next to the back of the block to the left of the oil filter if i recall, and put it back to working right.

is this the teal hacked one that was on ebay. had like 18's on it 1st listing. terrible looking seats, some chinese corners, etc…not bad, just didn't like they took a nice car and trashed it with junk.

 

Some good news to report - it seems that fixing what I thought was a totally unrelated problem has solved the initial issue with the charging system light.

Turns out my master cylinder was going bad, and apparently leaking a little break fluid onto the alternator as I drove. Put in a new master cylinder today and the battery/charging system light has not come back on since.

Anyone else ever had this happen?

 

Good to hear you fixed it! I've never heard of that one, before.

 

https://honda-tech.com/forums/showpo...4&postcount=12

 

check thermostat housing ground had that issues when i did my motor swap it will also keep ur car from starting while the battery ligt flashes and stays on