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Headache from AC system


So this is going to sound like an oddball question.

Last September, I started a job where I’m in my '98 Civic Hatchback most of the day. I was coming home with crazy headaches. I then had my cracked manifold replaced. Basically, pretty much the whole exhaust system has been replaced within the past couple years. I thought it was the exhaust fix that fixed my headaches. In late 2013 when it started getting cooler, I stopped using the AC around the same time the manifold was replaced. Either way, around this time, headaches stopped.

Role into Spring 2014. The past week I’ve been using the AC a lot because of the heat. The headaches have been coming back. Today I noticed a headache coming on pretty strong. It’s the same type of headache I was getting last year when I was using the AC. I rolled down the windows and turned off the AC. I noticed the headache subside after and hour and a half or so.

Question: is it possible to get headaches from my AC system? If so, what do I need to do? It’s getting hotter in St. Louis and my job requires that I’m in the car 5 days a week most of the day.

I used the heat most of our very cold winter. No headaches from that. Sometimes when I turn the AC on I can smell a faint “stale cocoa powder” smell. I realize this sounds crazy but would appreciate any help.

When the AC is on, the system is set to recirculate the air in the passenger cabin. When the heat is on, the system is set to introduce outside air into the passenger cabin which dilutes the air.

There has to be something in the passenger cabin that builds in concentration as the AC is used and the air is being recirculated.


There are battery operated CO detectors available I think. Might be worth the investment to see if there’s a carbon monoxide problem in the cabin.

I’m in agreement about checking this out with a battery operated CO detector. At least weed the “potentially lethal” part of this out.

If this does turn out to be a CO problem and the exhaust is not leaking anywhere then you might consider the possibility of the seal around the rear hatch not sealing as tight as it should be.

If it is not a CO issue then maybe you’re very sensitive to a potential mold problem due to the A/C evaporator. Hope that helps.

I too agree with the CO monitor suggestion.
And with the possibility of mold being the problem. But check the CO definitely. That problem, if you have it, can kill you.

Have a shop use the evap/smoke machine to look for exhaust leaks. Just because the manifold was replaced doesn’t guarantee all the leaks are gone