View Full Version : amp draw for heater motor

07-21-2008, 12:56 AM
Does anybody know the amp rating of the heater craft 2 tube heater box. I am seeing so much current draw when I flip my toggle, that it is shutting off my stereo like it does when I start the boat. I am suspicious that the heater motor may be going out, though it seems to work fine. Could it be the toggle switch??? Something is causing a major draw when I throw that toggle and energize the fan motor. I don't have a guage that measures amp draw, but my voltage drop at the batterry is aroung .55 volts when I turn on heater fan. Blower motor (for comparison) only drops voltage at battery .o5 to .1 volt (with boat not running).

Suggestions would sure be appreciated,


07-21-2008, 04:40 AM
Who installed the heater, and what did they connect to for power? A half volt drop shouldn't shut the stereo off. Does the stereo have a separate amp?

Measure the voltage at the stereo and turn the heater on. It could be a spike, not a drop that's causing it to mute, but if the display goes out, it's probably from the heater sharing the power and ground.

07-21-2008, 08:57 PM
From the Heatercraft web site. The 200H model current draws are: Low - 4.4, Med - 5.8, High - 8.5. Hope this helps. But, I agree with JimN. Check the things he mentioned.

07-22-2008, 08:14 PM
Thanks to you both for the reply. no amp on stereo and I lose sound and display. I know they all share a common ground, so I'll start by isolating the grounds. i will do more probing with the multi tester and let you know.

07-22-2008, 08:34 PM
If you run a heavier positive and negative wire to the dash to replace the existing ones, it would take care of the problem as long as the wires are sized correctly. That way, you don't need to isolate the grounds. If you find that the heater switch is spiking the voltage, that can be dealt with but if it has a relay to handle the current, it should be a Bosch "Green Stripe" model. That has spike suppression built in.

07-28-2008, 10:56 AM
Turns out the excessive draw had nothing to do with the heater fan motor. Multiple devices shared a ground, and I isolated them to a buss and ran a redundant 12 guage wire from buss to battery neg post. Problem went away, and volt meter picked up a volt on its display. Dash is back on and boat running fine. Lesson learned......don't link too many devices together on a common ground.

Thanks for the input guys.