Truck heater giving off funny smell?

Have a 1990 Ford truck. When I use the heater it gives off a funny odor. It smells like a mix of old car that has been sitting and old oil. Any ideas on what it may be?

That smell coming from your 1990 Fork truck is probably a mix of old car that has been sitting and old oil. Try starting your car more, getting your oil changed or rebuilding your engine block.

It is likely mold and all the good stuff baked in the heater core. The only solution is to remove the dashboard and clean the heater core or replace it.

Maybe be due to moisture from a leak at one of the hose fittings or in the heater core itself.

Sounds like you have mold in the air system. Or your heater core is leaking and your smelling anti freeze.

It's either antifreeze or mold.

Hope it is not leaking coolant…

You are smelling coolant, bud. Which means your heater core has failed.