High speed blower motor relay

[Matt L]

Hello all,
From what I’ve read the high speed blower is powered by a wire directly from the alternator to the high speed blower motor relay. I have two questions, first does this wire power anything else. I plan on running a heavier gauge wire direct to the relay any ideas on what size inline fuse would be necessary.
1978 Royal
Thanks ,Matt

 

[Christo]

Hello all,
From what I’ve read the high speed blower is powered by a wire directly from the alternator to the high speed blower motor relay. I have two questions, first does this wire power anything else. I plan on running a heavier gauge wire direct to the relay any ideas on what size inline fuse would be necessary.
1978 Royal
Thanks ,Matt

Wiring diagrams

 

[RF_Burns]

Besides the power going through the isolator, the only other power at the center point is going to the blower through the relay contacts. That is OEM wiring, but there maybe other wiring attached, such as on my coach I use the alternator power to detect the engine is running and activates the DRL (daytime running lights).

OEM used a #18 Fusible link rather than a fuse to the HVAC blower motor relay, Likely because a fusible link is weatherproof and less expensive than a high current weatherproof fuse. I'd think a 25 amp fuse would work.

If you need to replace the relay, you can use a relay similar to this one.

https://www.digikey.com/en/products/detail/panasonic-industry/CB1-R-M-12V/646989