Whenever I brew an Ale or light beer I get a very distinct alcohol taste, what could be the cause of this? When I brew dark beer I do not have this taste.
What tempurature did you ferement at? Higher fermentation tempuratures can cause this alcohol flavor
Yes, you are probably smelling fusel alcohols which are a result of too high of a fermenting temperature. They are not favorable in a beer and are the type which give people a bad headache. You should strive for 60-66F fermenting temp in the future.
My temp is right around 70, but now that our weather has gotten cooler I will but my fermenter in the garage were it is around 60. Why have I not had the alcohol taste with my porters, the temp has been right around 70 for them also.
My guess would be the bolder flavors of the porters are masking the off flavors
Despite years of brewing and never an infection or fusel problem, I had 2 in one month this summer. Damn if I wasn’t ready for the heat. Did everything like I always have but it just happens sometimes.
Besides high temperature fermentation, incorrect pitching can lead to fusel flavors as well.
When very active fermentation begins, it can raise the temp 6-10 degrees (or so I’ve read). The first few days or the most important.
I can say that after leaving both beers in the keg for a long time, they have subsided somewhat and while the beers aren’t great, they are drinkable and I’ve had no headaches or problems though I’m likely to pitch what’s left in the kegs when my fermenters are done and fill them with ‘unfusilized’ beer. 
My guess would be the bolder flavors of the porters are masking the off flavors[/quote]
This is likely the main reason.
However, in the past when I was not controlling my temps as much as I should have been, there were certain beers that just got more out of control than others. Likely due to the yeast strain, but who knows what other factors might have been involved.
Bottom line - don’t rely on ambiant temperatures to control the fermentation (unless they are quite low). You get your temps right, you will be making better beer every time.
And this improvement likely will include your porters etc as well. Even if you are not detecting the fusel alcohols too much in these beers, they would be there. And there are other minor defects (such as esters etc) that are likely there as well. Everything should taste cleaner in the end.
Don’t mean to hijack, but a natural follow up question to this thread is - can fusel alcohol flavors fade over time?
Yes, but it takes a long time. Time measured in years.
