GMC Sierra Evaporator

Dear Bob, I've no personal experience on working on such a truck. But, I've had a couple GM products. And been in the shop while a mechanic worked on such a vehicle. The evaporator is probably over the passenger's feet, and probably a lot of work to get at it. I know. I'm not much help.

Yes the dash has to come out. BUT one thing you can do prior to that is visit a dealer and buy the kit they sell for this very problem. It is a special type of disinfectant and includes tubes and nozzles to spray all of the inside of the housing. Then you use clear water to flush the drains out of the housing and usually it kills the problem.

Once clean you will want to keep the problem from starting again. The easy way is to run the heater for a few minutes after you run the A/C. The heat will dry out the core and plenum and stop the crud.

Thanks. Actually I was feeling "brave",LOL, yesterday and I did take the dash apart and found it. After 21 years the evaporator coil still looked brand new. I couldn't detect any odor coming from it nor was there any debris. Guess I'll have to look elsewhere.

Bob

Thanks. I've read about that stuff and might just try it. I did take the dash apart yesterday abut the evaporator looked shinny and new. No debris and no odor coming from that area. The smell must be coming from another area but I'll be darned if I know where. The vent passage ways that I could see were open and fairly clean for a 21 year old truck. It really smells like something dead. Any idea where else to look? We do have lots of snakes, geckos, and mice around here. But this has me stumped.

Bob

I hate to say it but it could be in the vent passages. Or in the air inlet in front of the windshield. There's no easy way dealing with anything under the dash. Maybe you could see if the smell is coming from one vent outlet.

Maybe something laying under the area where the wiper motor is.

Maybe try opening all the doors and windows so the smell doesn't spread all around. . Run the vents and sniff each one and see if the smell comes from

1 or 2 or all of them. If its one, well there's something in that one. Is there a floor vent like my old Chevy in the middle by the hump. Maybe something's down in there.

I don't want to belittle you either so I will ask. Is something dead under the front seat. I've had smells under the seat get sucked in the air inlet when it was on interior .

I'm thinking it's in the vent passages. The first thing I did was to take everything out of the passenger compartment and check under the seat. Couldn't find anything. The smell seems worse coming out of the center 2 vents. But I can smell it a bit weaker from the outer two vents. I did check the vent for the heater under the dash by the hump and it's clear. I don't smell anything coming from this vent nor anything when the heat is turned on. I'm thinking that you're right and something is inside in inlet by the windshield. That's about the only place I haven't taken apart yet to look. Might tackle it over this weekend. Thanks for everyone's help.

Bob

Best wishes. Well, at least it's clean.