The state regulator gives plain advice about a diminished value claim in Washington. File it against the at-fault party's insurer, not your own, unless your policy says otherwise.
Start with the Other Driver's Insurer
The Office of the Insurance Commissioner says you file a lost value claim against the insurer of the at-fault party. That is the normal route when someone else caused the crash. Get your repair records and a diminished value appraisal before you call the adjuster. A clear figure with a reason behind it is harder to brush off.
Moeller and Your Own Policy
Your own insurer is not always off the hook. In Moeller v. Farmers, from 2011, the state's top court held that the policy words at issue allow recovery for lost value. That result turned on the words in that Farmers policy.
The commissioner also warns that some auto policies do not cover lost value. Read your own terms line by line. If they match the Moeller wording, a first party claim may work.
Pure Comparative Fault
Washington does not bar a claim because you share the blame. Under RCW 4.22.005, your own fault lowers the award proportionally and never blocks recovery. A driver who was mostly at fault can still collect the part caused by the other side.
Three Years, Then Court
An action for injuring personal property must begin within three years under RCW 4.16.080(2). Talks with an insurer do not stretch that time.
The state minimum for damage to the property of others is $10,000 in any one accident. Repairs and lost value both draw on that one limit. A new car can drain it fast.
A natural person can bring a small claims case for up to $10,000 under RCW 12.40.010. If an insurer stalls or will not explain an offer, file with the Washington Office of the Insurance Commissioner.