No insurer shall refuse to renew a policy of insurance unless such insurer or its agent shall mail or deliver to the named insured, at the address shown in the policy, at least 45 days' advance notice of its intention not to renew. This section shall not apply if the insurer has manifested its willingness to renew, or in case of nonpayment of premium, or if the insured fails to pay any advance premium required by the insurer for renewal. Notwithstanding the failure of an insurer to comply with this section, the policy shall terminate on the effective date of any other insurance policy with respect to any automobile designated in both policies. Renewal of a policy shall not constitute a waiver or estoppel with respect to grounds for cancellation which existed before the effective date of such renewal. (Added 1971, No. 195 (Adj. Sess.), § 4; amended 1977, No. 223 (Adj. Sess.), § 8; 1989, No. 171 (Adj. Sess.), § 7, eff. Sept. 1, 1990.)