On what model you have, if Sunline Fan has not yet been able to respond to your VIN, here is one way to at least get close. See this 1984 brochure and look at the floor plans. That will narrow it down some. In 1984 they had a "lot" of floor plans.....
Sunline Coach Owner's Club - Sunline Owner's Files - 1984 Sunline Travel Trailer, Camper & Fifth Wheel
On the AC unit, inside the camper there is an air intake that has a cover over it and a filter behind it. Dometic has generally put a model and serial number of the unit up inside that area on a sticker. I have a newer one and is ducted air so the numbers are not even close. I believe in yours you may have a direct cieling mount system where the air enters and leaves right from the main unit.
Once you find the model and serial number, then a web search can turn up an AC cover. PPL Motor Holmes RV parts even has on line exploded diagrams of the AC systems. Dometic Duo Therm RV Air Conditioners
You can search the big parts catalog for the exploded diagrams but you need a model number.
They are actually called AC shroud in the parts books. And be prepaired for the cost. They are expensive buggers unless you can find a deal on E Bay. I bought a life time replacement one from frim in Canada and it was I think about $125. The Dometics ones area about $80 to $100 last I looked.
Hope this helps
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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