<PAGE>

                                                                    EXHIBIT 10.3

                                                                  Execution Copy

                                 AMENDMENT NO. 1
                                       to
                           RECEIVABLES SALE AGREEMENT
                         Dated as of September 11, 2003

                  THIS AMENDMENT NO. 1 ("Amendment") is entered into as of
September 11, 2003 by and among Armstrong Air Conditioning Inc., an Ohio
corporation ("Armstrong"), Lennox Hearth Products Inc., a California corporation
("Hearth") (each of Armstrong and Hearth, an "Originator" and collectively, the
"Originators"), and LPAC Corp. II, a Delaware corporation (the "Buyer").

                              PRELIMINARY STATEMENT

                  A.       The Originators and the Buyer are parties to that
certain Receivables Sale Agreement dated as of June 27, 2003 (as the same may be
further amended, restated, supplemented or otherwise modified from time to time,
the "Sale Agreement"). Capitalized terms used herein and not otherwise defined
shall have the meanings ascribed to them in the Sale Agreement.

                  B.       The Originators and the Buyer have agreed to amend
the Sale Agreement on the terms and subject to the conditions hereinafter set
forth.

                  NOW, THEREFORE, in consideration of the premises set forth
above, and other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties hereto hereby agree as follows:

                  SECTION 1.        Amendments. Effective as of the date hereof
and subject to the satisfaction of the conditions precedent set forth in Section
2 below, the Sale Agreement is hereby amended as follows:

                  (a)      Section 4.1(b)(ii)(1) of the Sale Agreement is
amended to delete the amount "$10,000,000" appearing therein and replace such
amount with "$5,000,000".

                  (b)      Section 5.1 of the Sale Agreement is amended to
delete paragraph (c) thereof in its entirety and replace it with the following:

                           "(c) Failure of such Originator or Performance
         Guarantor to pay any Indebtedness when due (after the passage of any
         applicable notice and grace period) in excess of $10,000,000; or the
         default (after the passage of any applicable notice and grace period)
         by such Originator or Performance Guarantor in the performance of any
         term, provision or condition contained in any agreement under which
         such Indebtedness was created or is governed, the effect of which is to
         cause, or to permit the holder or holders of such Indebtedness to
         cause, such Indebtedness to become due prior to its stated maturity;
         provided that, in the case of the Credit Agreement, such default has
         not been waived by the Required Lenders; or any such Indebtedness of
         such Originator or

<PAGE>

         Performance Guarantor shall be declared to be due and payable or
         required to be prepaid (other than by a regularly scheduled payment)
         prior to the date of maturity thereof."

                  (c)      Section 5.1 of the Sale Agreement is amended to
delete paragraph (f) thereof in its entirety and replace it with the following:

                  "(f) One or more final judgments for the payment of money in
         an amount in excess of $5,000,000, individually or in the aggregate,
         shall be entered against such Originator or Performance Guarantor on
         claims not covered by insurance or as to which the insurance carrier
         has denied its responsibility, and such judgment shall continue
         unsatisfied and in effect for sixty (60) consecutive days without a
         stay of execution."

                  (d)      Exhibit I to the Sale Agreement is amended to add the
following defined term thereto in the proper alphabetical order:

                  "Required Lenders" means, at any time, Lenders having
         Commitments under the Credit Agreement representing at least 66 2/3% of
         the Total Commitment or, for purposes of acceleration pursuant to
         Article 6 of the Credit Agreement, Lenders holding Loans or
         participation interests in Loans representing at least 66 2/3% of the
         aggregate principal amount of the Loans outstanding. Capitalized terms
         used in this definition shall have the meanings ascribed to them in the
         Credit Agreement.

                  SECTION 2.        Conditions Precedent. This Amendment shall
become effective and be deemed effective, as of the date first above written,
upon receipt by the Agent of four (4) copies of this Amendment duly executed by
each of the parties hereto.

                  SECTION 3.        Covenants, Representations and Warranties of
the Originators.

                  (a)      Upon the effectiveness of this Amendment, each of the
Originators hereby reaffirms all covenants, representations and warranties made
by it in the Sale Agreement, as amended, and agrees that all such covenants,
representations and warranties shall be deemed to have been re-made as of the
effective date of this Amendment.

                  (b)      Each of the Originators hereby represents and
warrants as to itself (i) that this Amendment constitutes the legal, valid and
binding obligation of such party enforceable against such party in accordance
with its terms, except as enforceability may be limited by bankruptcy,
insolvency, reorganization, moratorium or similar laws affecting the enforcement
of creditors' rights generally and general principles of equity which may limit
the availability of equitable remedies and (ii) upon the effectiveness of this
Amendment, that no event shall have occurred and be continuing which constitutes
a Termination Event or a Potential Termination Event.

                  SECTION 4.        Reference to and Effect on the Sale
Agreement.

                  (a)      Upon the effectiveness of this Amendment, each
reference in the Sale Agreement to "this Agreement," "hereunder," "hereof,"
"herein," "hereby" or words of like import shall mean and be a reference to the
Sale Agreement as amended hereby, and each

                                       2
<PAGE>

reference to the Sale Agreement in any other document, instrument or agreement
executed and/or delivered in connection with the Sale Agreement shall mean and
be a reference to the Sale Agreement as amended hereby.

                  (b)      Except as specifically amended hereby, the Sale
Agreement and other documents, instruments and agreements executed and/or
delivered in connection therewith shall remain in full force and effect and are
hereby ratified and confirmed.

                  (c)      The execution, delivery and effectiveness of this
Amendment shall not operate as a waiver of any right, power or remedy of the
Buyer, any Purchaser or the Agent under the Sale Agreement or any of the other
Transaction Documents, nor constitute a waiver of any provision contained
therein.

                  SECTION 5.        GOVERNING LAW. THIS AMENDMENT SHALL BE
GOVERNED AND CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE OF
ILLINOIS (INCLUDING, BUT NOT LIMITED TO, 735 ILCS SECTION 105/5-1 ET. SEQ., BUT
OTHERWISE WITHOUT REGARD TO CONFLICT OF LAW PROVISIONS).

                  SECTION 6.        Execution in Counterparts. This Amendment
may be executed in any number of counterparts and by different parties hereto in
separate counterparts, each of which when so executed and delivered shall be
deemed to be an original and all of which taken together shall constitute but
one and the same instrument.

                  SECTION 7.        Headings. Section headings in this Amendment
are included herein for convenience of reference only and shall not constitute a
part of this Amendment for any other purpose.

                                       3
<PAGE>

                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed on the date first set forth above by their respective
officers thereto duly authorized, to be effective as hereinabove provided.

                                    ARMSTRONG AIR CONDITIONING INC.

                                    By:____________________________
                                       Name:
                                       Title:

                                    LENNOX HEARTH PRODUCTS INC.

                                    By:_______________________
                                    Name:
                                    Title:

                                    LPAC CORP. II

                                    By:_______________________
                                    Name:
                                    Title:

Consented to by:

BANK ONE, NA (MAIN OFFICE CHICAGO),
as Agent

By:________________________________
Name: Maureen Marcon
Title: Director, Capital Markets

         Signature page to Amendment No. 1 to Receivables Sale Agreement