Evaporator Question Update 1/31 Got Some Parts

[gnvair]

My 87 Grand National never had it. My father's 88 Monte Carlo SS never had it either. I swapped the evaporator on the Monte Carlo when installed the Turbo Buick engine (the Turbo Buicks have a different evaporator). That was a 1 owner car with 39k miles on it. On the other hand my 78 Malibu was a relatively early production model (September of 77). It had the filter.

 

[69hurstolds]

You've seen 565bbchevy and oldsofb factory filters in pictures above. And they've been in there for 30+ years. They didn't look moldy to me. Not to knock your A/C guy, but GM knew there was a drain hole, too. They put it there. But there had to be a reason they felt they needed this filter...unless it was the Chief Engineer's idea, so nobody would be likely to argue against it. The picture evidence is clear to me that mold doesn't seem to be a huge issue using the filter. I'm not sure I like the idea of it disintegrating, though, but I guess nobody considered that going in. Those bits and pieces could end up on the heater core or in the cabin. So there's that to consider.

Not sure when the filter, if used, got in there on some of the units, but I would suspect it was from Harrison. I don't think it was at the sub-assembly level when they assembled the HVAC units to be shipped to the factories, because normally they would just take components out of the supply box and put the completed sub-assemblies in place. Maybe they put the foam seals on them and slapped them in. Not positive, though. Just musing.

As far as the evaporator staying wet, the fan should be moving some air across the evaporator most of the time anyway even when the compressor is off, unless the head unit switch is in OFF, as well as the filter being open cell foam which probably drains water fairly well anyway, so maybe that was a consideration? If your HVAC system is smelly or you suspect mold/mildew, you can always get some products made for evaporator cleaning for mold/mildew removal. Just take out the blower resistor or if you need a bit more room, take out the fan to at least access the upstream side of the evaporator.

This is how I would approach it. If you don't have it now, you likely won't have the clips and pins for it anyway. So why worry? If you've been running it without one with no issues, again, likely no worries. If you decide to put it in, it can't be any worse than the factory install since it would be new. An extraneous part that isn't used will not cause any issues. Your call. Either way you decide, always keep your flapper clean.

 

[84 W40]

I have replaced a quite a few at dealer, some had the foam some didn't. If the foam was in good shape I would put it back on. Can't recall why some cars had it some did not i have a box of service bulletins that i kepted maybe there's some info on it. I do remember replacing one in a 3rd gen f body and a 4th gen vette and both had mesh sceen glued to it, same purpose as the foam. Picture below shows the sceen around the evaporator

 

[69hurstolds]

Now I cannot compete with dealership mechanics replacing evaporators, but I've replaced very few evaporators in my own fleet and that was due to suspicions of mega metal particles in the system from destroyed R4 compressors. I've never had one blow a hole in it or anything.

Just wondering on the reasons evaporators would need all that replacing, in general? Do they spring leaks that often? Is it because people don't take care and bend/crack the tubing or screw up the threads on the fittings or...???

 

[mikester]

You've seen 565bbchevy and oldsofb factory filters in pictures above. And they've been in there for 30+ years. They didn't look moldy to me. Not to knock your A/C guy, but GM knew there was a drain hole, too. They put it there. But there had to be a reason they felt they needed this filter...unless it was the Chief Engineer's idea, so nobody would be likely to argue against it. The picture evidence is clear to me that mold doesn't seem to be a huge issue using the filter. I'm not sure I like the idea of it disintegrating, though, but I guess nobody considered that going in. Those bits and pieces could end up on the heater core or in the cabin. So there's that to consider.

Not sure when the filter, if used, got in there on some of the units, but I would suspect it was from Harrison. I don't think it was at the sub-assembly level when they assembled the HVAC units to be shipped to the factories, because normally they would just take components out of the supply box and put the completed sub-assemblies in place. Maybe they put the foam seals on them and slapped them in. Not positive, though. Just musing.

As far as the evaporator staying wet, the fan should be moving some air across the evaporator most of the time anyway even when the compressor is off, unless the head unit switch is in OFF, as well as the filter being open cell foam which probably drains water fairly well anyway, so maybe that was a consideration? If your HVAC system is smelly or you suspect mold/mildew, you can always get some products made for evaporator cleaning for mold/mildew removal. Just take out the blower resistor or if you need a bit more room, take out the fan to at least access the upstream side of the evaporator.

This is how I would approach it. If you don't have it now, you likely won't have the clips and pins for it anyway. So why worry? If you've been running it without one with no issues, again, likely no worries. If you decide to put it in, it can't be any worse than the factory install since it would be new. An extraneous part that isn't used will not cause any issues. Your call. Either way you decide, always keep your flapper clean.

Im probably going to leave it alone. Im really not into taking the box apart again.
One thing I will mention is before I decided to keep the wagon I had a friend of mine that wanted to buy it. He eventually bought a low mile driver that was in great shape. When he took it for a test drive I was sitting on the passenger side and noticed a couple of drops of liquid on the floor mat. Yup. it was antifreeze from the core leaking. The carpet looked a little faded on the center hump. It wasnt faded, it had stained from the leak. When I started to take it all apart to replace the core I found the main plug wrapped in a a wad of electrical tape. Once I had unwrapped it all I found the plug and wires in a melted mess. Just something else to fix. That was the start of me redoing the whole car. A heater core turned into a project car. LOL

 

[gnvair]

Just wondering on the reasons evaporators would need all that replacing, in general? Do they spring leaks that often? Is it because people don't take care and bend/crack the tubing or screw up the threads on the fittings or...???

As some who has made a living working on cars for almost 30 years now I can say most of the ones I have replaced were due to leakage via corrosion. Many times it looks like white speckles that is actual corrosion. The bottom of the cores is very common as debris accumulates and gets wet and some cases never dries. Some manufacturers have had real problems such as Chrysler and Jeep. Seen a bunch of 99-06 GM trucks with them fail as well. Did plenty of 80's and 90's GM J,L,N and W bodies. Had several that leaked refrigerant oil on to the core allowing dirt and grime to accumulate blocking air flow out of the vents.

 

[84 W40]

Now I cannot compete with dealership mechanics replacing evaporators, but I've replaced very few evaporators in my own fleet and that was due to suspicions of mega metal particles in the system from destroyed R4 compressors. I've never had one blow a hole in it or anything.

Just wondering on the reasons evaporators would need all that replacing, in general? Do they spring leaks that often? Is it because people don't take care and bend/crack the tubing or screw up the threads on the fittings or...???

I do remember 2 or 3 were leaking do to hair line cracks on the welds, the others were clogged fins with pine needles and other debris, no air passing threw it.

 

[Longroof79]

By looking inside the heater box, I'm assuming that the foam filter was meant more to keep excess debris out of the evaporator core more than being a moisture guard.

Mich, what you've described sounds like an out gassing condition. Many new cars seem to have a funky interior odor when they're brand new. I recall when I used to transport new cars, the odor in some of the cars was almost nauseating. Not a pleasant odor by any means.

 

[mikester]

By looking inside the heater box, I'm assuming that the foam filter was meant more to keep excess debris out of the evaporator core more than being a moisture guard.

Mich, what you've described sounds like an out gassing condition. Many new cars seem to have a funky interior odor when they're brand new. I recall when I used to transport new cars, the odor in some of the cars was almost nauseating. Not a pleasant odor by any means.

Thats exactly what it was Jack. And I think the plastics and materials used these days keep doing that forever. Ever notice the film on the inside of your windshield ? If you dont smoke and your windows are greasy inside its gotta be coming from somewhere.

 

[Longroof79]

Thats exactly what it was Jack. And I think the plastics and materials used these days keep doing that forever. Ever notice the film on the inside of your windshield ? If you dont smoke and your windows are greasy inside its gotta be coming from somewhere.

Mich,
Come to think of it, I do recall seeing the greasy film on the windshield. Again, I guess you can attribute that to the out gassing of the plastics.