<PAGE>

                                                                  Exhibit 10.19D

                                AMENDMENT NO. 6
                          TO SECURITIZATION AGREEMENTS

          AMENDMENT NO. 6 TO SECURITIZATION AGREEMENTS, dated as of August 25,
1999, among PAMECO SECURITIZATION CORPORATION, a Delaware company ("PSC"),
                                                                    ---
PAMECO CORPORATION, a Georgia company ("Pameco"), REDWOOD RECEIVABLES
                                        ------
CORPORATION ("Redwood") and GENERAL ELECTRIC CAPITAL CORPORATION, a New York
              -------
company ("GECC").
          ----

          WHEREAS, Pameco, as originator (in such capacity, the "Originator")
                                                                 ----------
and PSC are parties to a Receivables Transfer Agreement, dated as of April 29,
1996 (as heretofore amended, supplemented or otherwise modified, the "Transfer
                                                                      --------
Agreement");
---------

          WHEREAS, PSC, as seller (in such capacity, the "Seller"), Redwood, as
                                                          ------
purchaser (in such capacity, the "Purchaser"), GECC, as operating agent (in such
                                  ---------
capacity, the "Operating Agent") and collateral agent (in such capacity, the
               ---------------
"Collateral Agent") and Pameco, as servicer (in such capacity, the "Servicer")
-----------------                                                   --------
are parties to a Receivables Purchase and Servicing Agreement, dated as of April
29, 1996 (as heretofore amended, supplemented or otherwise modified, the
"Purchase Agreement");
-------------------

          WHEREAS, Redwood and GECC are parties to a Liquidity Loan Agreement,
dated as of April 29, 1996 (as heretofore amended, supplemented or otherwise
modified, the "Liquidity Agreement"; together with the Transfer Agreement and
               -------------------
the Purchase Agreement, the "Securitization Agreements"); and
                             -------------------------

          WHEREAS, the parties hereto desire to amend the Securitization
Agreements and certain ancillary documents and agreements referred to therein in
the manner set forth in this Amendment.

          NOW, THEREFORE, in consideration of the premises and the mutual
covenants contained herein, the parties hereto agree as follows:

                                   ARTICLE I
                                  DEFINITIONS

          SECTION 1.1  Definitions.  All capitalized terms used herein, unless
                       -----------
otherwise defined, are used as defined in the Purchase Agreement.

                                   ARTICLE II
                  AMENDMENTS TO PURCHASE AGREEMENT AND ANNEX X

          SECTION 2.1 Amendment to Exhibit H.  Exhibit H to the Purchase
                      ----------------------
Agreement is hereby amended by:

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<PAGE>

          (a) deleting subsection 1(a) in its entirety and replacing it with the
following:

          "(a) Servicer EBITDA.  As of the last day of each fiscal quarter of
               ---------------
     the Servicer, the Consolidated EBITDA for the preceding twelve consecutive
     fiscal months shall not be less than the amount set forth below opposite
     such period:

<TABLE>
<CAPTION>
          Fiscal Quarter Ending                 Amount
          ---------------------                 ------------
          <S>                                   <C>
          August 31, 1999                       $ 18,343,000
          November 30, 1999                     $ 18,724,000
          February 29, 2000                     $ 17,246,000
          For each fiscal quarter thereafter    $ 20,000,000"
</TABLE>
          (b) deleting subsection 1(c) in its entirety and replacing it with the
following:

               "(c) Fixed Charge Coverage Ratio.  As of the last day of each
                    ---------------------------
     fiscal quarter of the Servicer, the ratio of (i) Consolidated EBITDA to
     (ii) Consolidated Fixed Charges for the preceding twelve consecutive fiscal
     months shall not be less than the ratio set forth below opposite such
     period:

<TABLE>
<CAPTION>
          Fiscal Quarter Ending                 Ratio
          ---------------------                 -------------
          <S>                                   <C>
          August 31, 1999                       1.09 to 1.00
          November 30, 1999                     1.02 to 1.00
          February 29, 2000                     0.85 to 1.00
          For each fiscal quarter thereafter    1.25 to 1.00"
</TABLE>

                                  ARTICLE III
                                     WAIVER

          SECTION 3.1  Waiver.  The Operating Agent, Redwood and the Collateral
                       ------
Agent hereby waive the Termination Event and Event of Servicer Termination
arising under Sections 9.01(l) and 9.02(f) of the Purchase Agreement caused
solely by the Company's failure to comply with the covenants set forth in
Exhibit H to the Purchase Agreement for the fiscal quarter ended May 31, 1999.
The foregoing waivers are limited to the specific purpose for which they are
granted and shall not be construed as a consent, waiver or other modification
with respect to any other term, condition or other provisions of any Related
Document or any other Termination Event and Event of Servicer Termination now or
hereafter existing.

                                   ARTICLE IV
                         REPRESENTATIONS AND WARRANTIES

          SECTION 4.1  Representations and Warranties of PSC and Pameco.  Each
                       ------------------------------------------------
of PSC and Pameco represents and warrants that:

          (a) this Amendment No. 6 has been duly authorized, executed and
delivered by each such party which is a signatory thereto;

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          (b)  this Amendment No. 6 constitutes the legal, valid and binding
obligation of each such party which is a signatory thereto; and

          (c) each of the representations and warranties of such party set forth
in the Securitization Agreements is true and correct as of the Amendment
Effective Date (as defined below) and on such Amendment Effective Date is also
made with respect to the Insurer; provided, that references in the
                                  --------  ----
Securitization Agreements to the Purchase Agreement and to the Transfer
Agreement, shall be deemed references to the Purchase Agreement as amended by
this Amendment No. 6 and to the Transfer Agreement as amended by this Amendment
No. 6, respectively.

          SECTION 4.2  Representations and Warranties of Redwood.  Redwood
                       -----------------------------------------
represents and warrants that:

          (a) this Amendment No. 6 has been duly authorized, executed and
delivered by Redwood;

          (b)  this Amendment No. 6 constitutes the legal, valid and binding
obligation of Redwood; and

          (c)   each of the representations and warranties of Redwood set forth
in the Securitization Agreements is true and correct as of the Amendment
Effective Date (as defined below); provided, that references in the
                                   --------  ----
Securitization Agreements to the Purchase Agreement and to the Transfer
Agreement, shall be deemed references to the Purchase Agreement as amended by
this Amendment No. 6 and to the Transfer Agreement as amended by this Amendment
No. 6, respectively.

                                   ARTICLE V
                              CONDITIONS PRECEDENT

          SECTION 5.1  Conditions Precedent.    This Amendment No. 6 shall
                       --------------------
become effective (the actual date of such effectiveness, the "Amendment
                                                              ---------
Effective Date") as of the date first above written subject to satisfaction of
--------------
the following conditions precedent in form and substance satisfactory to the
Operating Agent:

          (a) Counterparts hereof shall have been duly executed and delivered by
the parties hereto;

          (b) the Operating Agent shall have received a certificate of the
Secretary or an Assistant Secretary of each of the Seller and the Servicer,
dated as of the Amendment Effective Date, and certifying (i) the names and true
signatures of the officers authorized on its behalf to sign this Amendment No.
6, (ii) a copy of such party's certificate of incorporation and by-laws, and
(iii) a copy of the resolutions of the board of directors of such party
approving this Amendment No. 6 and the related transactions to which it is a
party, all in form and substance satisfactory to the Operating Agent.  Such
certificate shall state that the resolutions thereby

                                      -3-
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certified have not been amended, modified, revoked or rescinded as of the date
of such certificate;

          (c)  the Operating Agent shall have received an Officer's Certificate
from each of the Seller and the Servicer in the forms of Annexes A-1 and A-2
hereto, respectively;

          (d) PSC shall have received a certificate of the Secretary or an
Assistant Secretary of the Originator, dated as of the Amendment Effective Date,
and certifying (i) the names and true signatures of the officers authorized on
its behalf to sign this Amendment No. 6,  (ii) a copy of the Originator's
certificate of incorporation and by-laws, and (iii) a copy of the resolutions of
the board of directors of the Originator approving this Amendment No. 6 and the
related transactions to which it is a party.  Such certificate shall state that
the resolutions thereby certified have not been amended, modified, revoked or
rescinded as of the date of such certificate; and

          (e) PSC and Pameco shall have taken such other actions and provided
such documentation as the Operating Agent may request.

                                   ARTICLE VI
                                 MISCELLANEOUS

          SECTION 6.1  Counterparts.  This Amendment No. 6 may be executed on
                       ------------
any number of separate counterparts and all of said counterparts taken together
shall be deemed to constitute one and the same instrument.

          SECTION 6.2  GOVERNING LAW.  THIS AMENDMENT NO. 6 SHALL BE GOVERNED
                       -------------
BY, AND CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE
STATE OF NEW YORK.

          SECTION 6.3  Expenses.  Pameco agrees to pay and reimburse the
                       --------
Operating Agent for all of its out-of-pocket costs and expenses incurred in
connection with the negotiation, preparation, execution, and delivery of this
Amendment No. 6, including the reasonable fees and expenses of counsel to the
Operating Agent and the Collateral Agent.

                            [signature page follows]

                                      -4-
<PAGE>

IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 6 to be
duly executed and delivered by their proper and duly authorized officers as of
the day and year first above written.

                              PAMECO SECURITIZATION CORPORATION

                              By ________________________
                                   Title:

                              REDWOOD RECEIVABLES CORPORATION

                              By  _______________________
                                   Title:

                              PAMECO CORPORATION

                              By  _______________________
                                   Title:

                              GENERAL ELECTRIC CAPITAL CORPORATION,
                              as Operating Agent and Collateral Agent

                              By  _______________________
                                   Title:

                              GENERAL ELECTRIC CAPITAL CORPORATION,
                              as Liquidity Agent

                              By  _______________________
                                   Title:

                              GENERAL ELECTRIC CAPITAL CORPORATION,
                              as Letter of Credit Agent and
                              Letter of Credit Provider

                              By  _______________________
                                   Title:



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ANNEX A-1

                    FORM OF OFFICER'S CERTIFICATE OF SELLER
                    ---------------------------------------

                       Pameco Securitization Corporation

                             Officer's Certificate

          I, [Name of Officer], the duly elected [Insert Title] of Pameco
Securitization Corporation (the "Seller"), hereby certify pursuant to Section
5.1(c) of Amendment No. 6 to Securitization Agreements, dated as of the date
hereof ("Amendment No. 6"; capitalized terms used but not defined in this
Officer's Certificate having the meaning set forth in Amendment No. 6), between
the Seller, Pameco Corporation, Redwood Receivables Corporation (the
"Purchaser") and General Electric Capital Corporation, and for the benefit of
the Purchaser, the Operating Agent and General Electric Capital Corporation, as
follows:

          (1) after giving effect to the effectiveness of Amendment No. 6, no
Termination Event or Incipient Event will have occurred and be continuing; and

          (2)  the representations and warranties of the Seller contained in
Section 4.01 of the Purchase Agreement, in the Transfer Agreement and in any
other document, certificate or financial or other statement delivered by the
Seller in connection with the Purchase Agreement or the Transfer Agreement are
true and correct in all material respects and with the same force and effect as
though such representations and warranties had been made as of such date, except
to the extent any such representations and warranties relate solely to an
earlier date.

          IN WITNESS WHEREOF, I have signed and delivered this Officer's
Certificate this ___ day of August, 1999.

                              PAMECO SECURITIZATION CORPORATION

                              By:_________________________
                                 Name:
                                 Title:

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ANNEX A-2

                   FORM OF OFFICER'S CERTIFICATE OF SERVICER
                   -----------------------------------------

                               Pameco Corporation

                             Officer's Certificate

          I, [Name of Officer], the duly elected [Insert Title] of Pameco
Corporation (the "Servicer"), hereby certify pursuant to Section 5.1(c) of
Amendment No. 6 to Securitization Agreements, dated as of the date hereof
("Amendment No. 6"; capitalized terms used but not defined in this Officer's
Certificate having the meaning set forth in Amendment No. 6), between Pameco
Securitization Corporation, the Servicer, Redwood Receivables Corporation (the
"Purchaser") and General Electric Capital Corporation, and for the benefit of
the Purchaser, the Operating Agent and General Electric Capital Corporation, as
follows:

          (1) after giving effect to the effectiveness of Amendment No. 6, no
Termination Event or Incipient Event will have occurred and be continuing; and

          (2)  the representations and warranties of the Seller contained in
Section 4.01 of the Purchase Agreement, in the Transfer Agreement and in any
other document, certificate or financial or other statement delivered by the
Seller in connection with the Purchase Agreement or the Transfer Agreement are
true and correct in all material respects and with the same force and effect as
though such representations and warranties had been made as of such date, except
to the extent any such representations and warranties relate solely to an
earlier date.

          IN WITNESS WHEREOF, I have signed and delivered this Officer's
Certificate this ___ day of August, 1999.

                              PAMECO CORPORATION

                              By:_________________________
                                 Name:
                                 Title:

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