It's tough to explain but if I turn the fan to max setting (4) the car starts pulsing, like a sign wave. I can't tell if RPM is fluctuating. It's most noticeable on cold start when it's fast idling but it happens all the time. If I have the fan turned up and a coast in gear there's a slight hesitation, idk if it's related. Is this a grounding issue? The blower does need to be replaced, it makes bearing noise or something for the first couple minutes it's on. I'm worried I have a tricky electrical problem. I tried recording but all you hear is air from the blower. Engine bay grounds are clean and match battery voltage. Any chance changing the motor would help?

I'm not sure I would notice with stock motor mounts. I have urethane torque mount inserts and filled the rear and trans mounts with flex seal so there is more vibration than stock. Getting the car re-tuned soon but I want to fix this first in-case it messes with the tune at all.

97 civic ex, original motor, 7psi ebay turbo, p60 +vtec hondata s300 v1, 243k miles

 

Look in the data. What’s the battery voltage when this is happening? When it’s not?

 

Battery, whether blower is on or off, is fluctuating pretty fast between 14.16v and 14.35v. Not perfectly rhythmic like what I'm hearing. ELD with blower off is 3.5v, blower on 2.6v, does that seem weird?

I'm not seeing anything odd with RPM, ignition seems relatively smooth but it retards about 6 degrees when I turn blower to max and ELD drops.

Maybe my battery is crap and when I quickly add a bunch of load the alternator has to work extra hard? Or a bad alternator idk. I drive it every day, last time battery died was during a compression test.

Whatever the issue (if it's an issue) it's possible the fan is only making it bad enough for me to notice. IDK how to describe the noise other than the vibration from motor is like a dubstep bass wobble going WUBWUBWUBWUBWUB

 

Doesn't sound like your alternator or the alternator power wire based on your data.

Good checking on the ELD too. The .9V change is worth about 16A. I'd have a look at your blower fan. That seems awful high.

How the ELD voltage signal correlates to system amperage, btw:

 

Oh nice, saving that.

Blower needs replacing anyway so I'll go ahead and do that, and test wires while I'm there.

Here's a pic of my cold start, is BAT supposed to be spiky like that? I wonder if it's my cheapo jumper harness.

 

Do that first and the resistor (I think it’s called transistor) which is easy to do from under the dash behind the glove compartment.

 

The battery voltage looks pretty normal. It always moves around a little bit:




97's still had a resistor. Only needs to be replaced if one or more of the run positions are not working. 99+ have a transistor. It either works or it doesn't. Can't say I've ever seen one need replacement.