Heater relay – 20 amp or 70 amp?

[markeb01]

I’m going to be wiring a relay in my heater circuit soon. I’m running a Fiero heater fan motor, and can’t find the amperage draw anywhere.

I have a Hella relay rated at 20/30; 12/24V. I’m not sure if this means 20 amps at 12 volts and 30 at 24 volts, or it’s good for 20-30 amps.

I also have a Signal-Stat relay that was used in my air conditioning wiring. I’d prefer to save this for a headlight relay addition.

Please advise if either of these are suitable for a heater circuit, or if I should buy a relay with a different rating.

[protrash64]

I understand your question about the rating; it seems weird. To me, if it's rated for 30a, its rated for less, too If that makes any sense. 30a equates to 10g wire, and 10g is fairly rare in automotive circuits, in my experience(the exception being audio, air bags, and hydraulics).

I would use the relay for the fan and make sure to use a breaker or fuse in the power side before the relay. If the fan does draw too much it will trip/burn the fuse and save the relay, fan, and all the associated wiring and potentially the vehicle, too.

[markeb01]

Thanks for the feedback. I finally discovered the meaning of the rating after a lot of internet searching. The 20 amp rating is for the 87a (normally closed) terminal, and the 30 amp rating is for the 87 (normally open) terminal, which is most commonly used. So for my application it really is a 30 amp relay.