[samdief]

I have a 2005 CR-V, and as the title states I've been trying to track down what might be causing my headlights to dim when I press the gas while the car is in Drive (D).


Symptoms:
The symptoms are when I let my foot off the gas, there is about a 1-second delay in which the headlights are at their normal operating brightness, and then the headlights suddenly dim (guessing its a drop in voltage). However, the other weird part is that I can feel the car sort of jolt, sometimes steering the car very slightly to the left. Both of these happen simultaneously without fail. The alternator is fairly new (8 months old) and hasn't had trouble charging the battery and hasn't had any starting issues. Additionally, the headlights immediately dim when pressing the gas again (which is weird since there should be an increase in voltage).

Voltage readings:
When my car is off, my battery voltage read: 13.24v

When idle with no accessories on, it read: 14.63v

When idle with headlights on it read: 14.70v


Any thoughts?

P.S.: Considering rebuilding the voltage regulator and replacing the load detector at this moment.

 

[otto888man]

I would suggest to check all of the ground points. Any corrosion on the battery terminals? Was anything done before this happened? How about the interior lights does it also dim when the headlights dim too? Try measuring the voltage from the battery positive terminal and the body ground see what voltage you get. Also check for AC voltage see if what do you get? How about when the engine is rev up i.e. 3000 RPM? What voltage do you get? Try unplugging the Terminal going into the Alternator not the Red cable main Battery cable. Be sure you have the Negative Battery Terminal before doing this. From the symptoms you are describing it might be an Alternator Issue. I hope this helps. Keep us posted.

 

[samdief]

I would suggest to check all of the ground points. Any corrosion on the battery terminals? Was anything done before this happened? How about the interior lights does it also dim when the headlights dim too? Try measuring the voltage from the battery positive terminal and the body ground see what voltage you get. Also check for AC voltage see if what do you get? How about when the engine is rev up i.e. 3000 RPM? What voltage do you get? Try unplugging the Terminal going into the Alternator not the Red cable main Battery cable. Be sure you have the Negative Battery Terminal before doing this. From the symptoms you are describing it might be an Alternator Issue. I hope this helps. Keep us posted.

Thanks for all of the suggestions! I will try a few of those tomorrow morning. I took it out for a drive again tonight and it wasn’t having the problem until the end of my drive. But before then I wasn’t having any power issues, headlights weren’t dimming at all. I tried a bunch of things too, tried turning on A/C, blower on high, etc. nothing triggered it to start dimming the lights when letting off the gas. It wasn’t until the end of my drive when it started. Also yes the interior lights, dash, radio lights do dim. Definitely frustrating that I can’t reproduce the issue every time. I’ll try to get the voltages when it starts acting up.

 

[otto888man]

Try this hook a jumper cable only on the negative terminal battery to the engine block see if that resolves your issue.

We'll get to the bottom of this. The hardest is an Intermittent issue to solve.

 

[Traylaw]

There are two main ground cables that come off the negative battery post. One bolts to the vehicle's chassis and the other bolts to the transmission case. Both of cables must be making a solid low resistance connection or it will cause strange electrical problems.
There is a third (smaller wire) ground connection on the passenger side engine compartment that connects the engine block to the chassis. You will find this wire (#12 AWG) running along the upper engine mount.

 

[samdief]

There are two main ground cables that come off the negative battery post. One bolts to the vehicle's chassis and the other bolts to the transmission case. Both of cables must be making a solid low resistance connection or it will cause strange electrical problems.
There is a third (smaller wire) ground connection on the passenger side engine compartment that connects the engine block to the chassis. You will find this wire (#12 AWG) running along the upper engine mount.

Awesome! I'll check those and clean them. Do you recommend just using sandpaper or something if they are corroded?

 

[Traylaw]

Awesome! I'll check those and clean them. Do you recommend just using sandpaper or something if they are corroded?

Yes, sandpaper, scotch bright pad, whatever. A little Vaseline or silicone grease will help to keep the connections from oxidizing in the future. Doesn't hurt to take the connections apart and clean them up every 17 years or so.🙂

 

[Carbuff2]

Doesn't your V 'run off the battery' under low voltage loads? Ours does.

So, after the car warms up, lights off/low fan you should see ~12.5V, lights on you should see ~14.5VDC.

+++++++++++

That statement aside, cleaning the grounds is a good idea. While you are under the car, look for any abrasion or tight wire looms that could be shorting.

 

[samdief]

I've checked most of my grounds, including the one right next to the battery, and everything looked ok. I'm noticing that it consistently will start dimming about 10 minutes into my drive. This will continue until I park the car for a while and will start again about 10 minutes into the drive or so. Very curious now if it could be temperature related...? Any thoughts on what could start pulling harder on the electrical system when the car gets warm? Again, this only happens when pressing on the pedal.

 

[Traylaw]

Have you considered the drive belt slipping or a worn out belt tensioner?

 

[samdief]

Have you considered the drive belt slipping or a worn out belt tensioner?

Oh, that's a good thought. Perhaps the belt warms up just enough that it starts to slip.

 

[Carbuff2]

Can you tell if the dimming occurs in concert with the A/C compressor engaging? (It will work in any of the defrost selections, with no other indicator)