There is no monetary benefit to you having auto or HELOC debt. First, the key is knowing what is considered good debt and bad debt which affects your credit score. You are paying auto interest monthly---do you get any return on that money? HELOC---are you receiving any return on that? The choice would be a matter of what are you getting back in return in your pocket to hold certain debt.
You may want to substaintially pay down or pay off the auto loan then work toward the same on the HELOC---whichever has the highest interest rate. Continue to sock away as much as possible toward your home purchase budget. A lot can happen in your life within 18 months. Being free of debt and those payments when times get tough should be a part of your overall plan as well. Good to luck to you!