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                                 Exhibit 10.4
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                          CONVERTIBLE PROMISSORY NOTE



$1,500,000                                                    September 20, 2001
                                                           Irwindale, California



          FOR VALUE RECEIVED, Amerigon Incorporated, a California corporation
(the "Borrower"), promises to pay to the order of Big Beaver Investments LLC, a
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Delaware limited liability company (the "Lender"), the principal amount of One
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Million Five Hundred Thousand Dollars ($1,500,000), or, if less, the aggregate
principal amount of the Loan Advances (as defined in the Credit Agreement
referred to below) made by the Lender to the Borrower pursuant to the Credit
Agreement.

          The Borrower also promises to pay interest on the unpaid principal
amount hereof from the date hereof until paid at the rates and at the times
which shall be determined in accordance with the provisions of the Credit
Agreement. Any interest not paid when due shall be compounded and shall
thereafter accrue interest at the rates and at the times which shall be
determined in accordance with the provisions of the Credit Agreement. All unpaid
amounts of principal and interest shall be due and payable in full on the Final
Maturity Date (as defined in the Credit Agreement).

          All payments of principal and interest in respect of this Note shall
be made in lawful money of the United States of America in same day funds at the
office of the Lender located at 801 W. Big Beaver Road, Suite 201, Troy,
Michigan 48084, or at such other place as shall be designated in writing for
such purpose in accordance with the terms of the Credit Agreement. Until
notified of the transfer of this Note, the Borrower shall be entitled to deem
the Lender or such person who has been so identified by the transferor in
writing to the Borrower as the holder of this Note, as the owner and holder of
this Note. Each of the Lender and any subsequent holder of this Note agrees that
before disposing of this Note or any part hereof, it will make a notation hereon
of all principal payments previously made hereunder and of the date to which
interest hereon has been paid on the schedule attached hereto, if any; provided,
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however, that the failure to make notation of any payment made on this Note
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shall not limit or otherwise affect the obligation of the Borrower hereunder
with respect to payments of principal or interest on this Note.

          This Note is referred to in, and is entitled to the benefits and
subject to the terms and conditions of, that certain Credit Agreement dated as
of September 20, 2001 (as amended, modified, renewed or extended from time to
time, the "Credit Agreement") between the Borrower and the Lender. The Credit
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Agreement, among other things, (i) provides for the making of a term loan by the
Lender to the Borrower in an aggregate amount not to exceed at any time
outstanding the U.S. dollar amount first above mentioned (the "Loan"), the
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indebtedness of the Borrower resulting from the Loan being evidenced by this
Note, (ii) contains provisions for acceleration of the maturity hereof upon the
happening of certain stated events and (iii) permits the prepayment of the Loan
by the Borrower prior to maturity.

          The Borrower's obligations under this Note are also secured by all
assets of the Borrower pursuant to the terms of the Credit Agreement and the
Collateral Documents (as defined in the Credit Agreement). The terms and
conditions of the Credit Agreement and the Collateral Documents are incorporated
herein by this reference.

          This Note is subject to conversion into the Common Stock of the
Borrower as further provided in the Credit Agreement.

          The terms of this Note are subject to amendment only in the manner
provided in the Credit Agreement.

          No reference herein to the Credit Agreement or the Collateral
Documents, and no provision of this Note or such agreements shall alter or
impair the obligation of the Borrower, which is absolute and unconditional, to
pay the principal of and interest on this Note at the place, at the respective
times, and in the currency herein prescribed.

          The Borrower promises to pay all reasonable costs and expenses,
including reasonable attorneys' fees, incurred in the collection and enforcement
of this Note. The Borrower hereby consents to renewals and extensions of time at
or after the maturity hereof, without notice, and, subject to the Credit
Agreement, hereby waives diligence, presentment, protest, demand and notice of
every kind and, to the full extent permitted by law, the right to plead any
statute of limitations as a defense to any demand hereunder.

          IN WITNESS WHEREOF, the Borrower has caused this Note to be executed
and delivered by its duly authorized officer, as of the date and the place first
above-written.


                                             AMERIGON INCORPORATED,
                                             a California corporation


                                             By:    /s/ Richard A. Weisbart
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                                                 Richard A. Weisbart,
                                                 President & CEO

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