I assume you mean that Hartford is the insurer of another vehicle that was at fault for causing the accident. Insurance companies will sometimes make a total loss offer and insist on deducting "salvage value" and making you keep the car. This is not legal because the measure of damages for a total vehicle is "fair market value", not "fair market value less salvage value". I would let Hartford know you are aware of this and insist that they pay full fair market value (if they just don't want the truck, tell them you will keep it after they pay you full FMV and you can then sell it to a salvage yard).
Whether they continue to be responsible to pay for a rental car will depend on whether their offer of settlement was reasonable. So if they are offering less than FMV, or are insisting on you keeping the vehicle and deducting salvage when they don't have a right to do that, arguably they are still on the hook for the rental.
The problem with all of these issues is if they insist they have offered FMV, insist they can deduct salvage value, and/or stop paying for the rental, your only choice would be to sue them, which may not be practical way to resolve your property damage claim.
If you were injured in the collision, you can consult a personal injury attorney who can help with PD issues.
Is this your insurance or a 3rd party insurance? If it is your insurance, you may have a bad faith claim. If not, they are simply trying to hang on to as much money as possible. In either case you should consider contacting an attorney to assist you with your claim. Best of luck.
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