Dometic - FreshJet ADB Spacer Kit for RV Roofs Over 5.5 in. - Part# 9620006638

The Dometic FreshJet ADB Spacer Kit, part# 9620006638, is the genuine Dometic accessory that lets a FreshJet air distribution box (ADB) mount correctly on an RV roof thicker than 5.5 in. (140 mm). A standard FreshJet ADB installation covers roof thicknesses of 1.25 to 5.5 in. (32 to 140 mm). If you measure more than 5.5 in. from the rooftop unit basepan down to the ceiling opening, the factory bolts and foam dividers will not reach — this kit adds the extra foam and longer hardware you need.

Each kit contains two 1.2 in. (30 mm) foam dividers and four 9-1/2 in. long mounting bolts. The foam dividers stack behind the ceiling assembly to close the gap, and the longer bolts replace the standard ADB bolts so all four can still be torqued down evenly.

What's Included

• 2 x Dometic foam dividers, 1.2 in. (30 mm) each
• 4 x mounting bolts, 9-1/2 in. long, with washers

The air conditioner, air distribution box, thermostat, and ceiling template are not included — this is an accessory kit only.

Do You Need This Kit?

1. Measure your roof thickness from a flat surface of the installed rooftop unit's basepan down to the ceiling opening inside the RV.
2. 1.25 in. to 5.5 in. (32–140 mm): the standard FreshJet ADB hardware is sufficient. You do not need this kit.
3. Greater than 5.5 in. (140 mm): order part# 9620006638.

Thick sandwich roofs, roofs with added insulation, furred-down ceilings, and framed openings are the usual reasons a coach lands above 5.5 in.

Technical Specifications

Compatible Dometic FreshJet Models

Dometic lists spacer kit 9620006638 as the optional roof-thickness accessory in the FreshJet 3 and FreshJet 4 Series ADB installation manual, which covers these models:

Confirm part number 9620006638 against your own Dometic installation manual or parts diagram before ordering. If your model is not on this list, contact us with your air conditioner model number and measured roof thickness and we will check it for you rather than guess.

Installation Notes

• Shut off the gas supply, disconnect 115 VAC power from the RV, and disconnect the positive (+) 12 VDC battery terminal before working on the ceiling assembly.
• Stack the foam dividers as required to fill the gap between the rooftop unit and the ceiling opening.
• Swap in the four 9-1/2 in. bolts in place of the standard-length ADB bolts.
• On FreshJet FJX3473 and FJX3573, torque all four mounting bolts evenly to 22.2 in. lbs (2.5 N·m). Over-torquing crushes the foam and causes air leaks and rattles.
• Framing stock around the roof opening must be 0.75 in. (19 mm) or thicker to support the assembly.
• Always follow your model's Dometic installation manual as the final authority. Download the Dometic FreshJet 3 & 4 Series ADB installation manual (PDF) — hosted here for free, no registration required.

Frequently Asked Questions

How do I measure my RV roof thickness for a FreshJet ADB?

Measure from a flat surface of the installed rooftop unit's basepan down to the ceiling opening inside the RV. Anything over 5.5 in. (140 mm) requires spacer kit 9620006638.

How many foam dividers and bolts come in part# 9620006638?

Two 1.2 in. (30 mm) foam dividers and four 9-1/2 in. long bolts.

Is the spacer kit included with a new FreshJet air conditioner?

No. Dometic lists it as an optional accessory that is not included, which is why it has to be ordered separately.

Can I use longer bolts from the hardware store instead?

We do not recommend it. The kit bolts are matched to the ADB's clamping range and torque spec, and generic hardware can crush the foam or fail to seal the ceiling assembly.

Will this work on a ducted installation?

This kit is for the FreshJet air distribution box (non-ducted ceiling assembly). If you have a ducted ceiling assembly, contact us with your model number before ordering.

Is this a genuine Dometic part?

Yes. This is the Dometic-branded accessory kit sold under part number 9620006638.

Why Buy From Elkhart RV Parts?

We are in Elkhart, Indiana, the RV capital of the world, and we specialize in the hard-to-find service and accessory parts that make a repair actually finish. Every listing is built around the exact OEM part number so you are not guessing from a photo.

Sources

• Dometic FJX ADB Installation and Operating Manual, FreshJet 3 & 4 Series (Dometic form no. 4450026413, revised 2023-10-11) — kit contents, roof thickness ranges, compatible model list, and ADB bolt torque specifications. Download the manual (PDF, 28 pages).
• Dometic Air Conditioner Installation Manual (Brisk II / High Performance / Blizzard NXT / FreshJet, incl. FJX3473 & FJX3573) — optional parts listing for 9620006638: https://manuals.plus/dometic/b79516-air-conditioners-manual