To start off a little background. I have a 89 CRX dx with a b18a1 swap. I did the swap about two years ago. Everything has been running great with no problems. About a month ago the problem started. While driving and turning on the headlight the tach would drop to nothing and the temp gauge would max out. If you rev the engine it would be fine and all was well. Then about a week or so after it started the little box on the back of the inside fuse box fried. I swapped it out with one I had lying around and all has been fine. I get home from a two week vacation and the problem is back. I cannot drive at night because the headlight dim so low I cannot see the road.

If you didnt want to read the above here is a quick rundown.
This all happens while driving with lights on or hitting the brakes.
Issues:
1. All lights dim
2. Tach either bounces or drops to zero
3. Temp gauge maxes out.

Tried fixes
1. Triple checked all grounds. I removed all of them, sanded both sides to make better contact.
2. Looked inside control box on fuse box and nothing is burnt.

And help would be great as I am stumped.

 

Battery,Alternator,battery connections.

Try those lmk

 

well I just put a new battery in. Checked the taillights and cleaned the connections. I think it is the alt. Because when I have it running it would meter between the body ground and the B post and its less then 12 volts at all rpm. But the auto parts store says its fine. Whats the best way to check it? I also did discover that it will still have the issue even if the car is off but the key on.

 

i had the exact same issue with my 89dx and mine was the ground junction blocks by the headlights... i also did the eld bypass at the same time...highly reccomended

 

I will double check the ground blocks again and as for the ELD bypass. What is it?

 

its basically a circuit that utilizes a relay to put a resistored ground circuit to the electronic load detector in the under hood f/b allowing the ecu to fully field the alternator and put out higher charging voltage even at low rpm ....good for stereos or night time driving @ low rpm so your headlights dont dim @ idle

 

How do I bypass it to see if it helps? do I just unplug it or cut some wires

 

i can guarantee it won't do anything until you get your ground issues fixed ...also one other thing to check ...take a thin gauge wire from your neg battery terminal and touch it to a chassis ground with the car idling ...if grounds are bad you should see a spark if they are good however you should see nothing ....also remember our fuse boxes under dash are prone to loose fuses that will show good under a test but fail intermittently under normal use ...so don't be afraid to get in and start wiggling connections until something happens

 

Sounds like grounds. I would make new ground cable, clean ground points and replace battery conection terminals.

 

did you get it figured out yet?

 

Well I got a new batt and a new alt. Still had the problem. Turns out it was my main ground from the battery. I had double check the connection and cleaned them up and all was good. Or so I thought. The cable had oxidized inside sheath and started falling apart but made connections at times. Made a new cable up and the problem is gone.