Relay and Fuse Solution Bussman Power Relay Module

[68nate]

Didn't know if anyone had seen these yet, I've been looking for something like this for quite a while. Made by cooper Bussman- Power Relay Module and Power Fuse Module. Just bought a few of each from www.waytekwire.com out of minneapolis. Each Power Relay Module has a 70 amp relay with a fuse built in for relay circuit protection and another fuse that will handle 70 amps and a sealed fuse cover. Gonna use these for my Mark VIII fan controller bypass and headlights. Gonna use the Power Fuse Module for system circuit protection to replace the big bulky plastic covered MAXI fuse that came with my painless wiring harness. Nice little package to get rid of relays and fuse holders dangling from screws.

Oh yeah, they're cheap too!! $23 for the relay module $11 for the fuse module

http://order.waytekwire.com/productd...E%20-%20STUDS/

http://order.waytekwire.com/productd...0-%20J%20CASE/

[grobb284]

They are a very nice product. Using them in conjunction with their RTMR combination fuse and relay panels for wiring my car.

[DarkoNova]

So technically I could use that relay module as a junction block for switched power on one terminal and constant power on the other terminal? That's pretty awesome. Any recommendations on fuse sizes since it says fuses aren't included?

[Larry Callahan]

Those are cool! I just wish the were not almost 5" long.

[grobb284]

I'm using them exactly as you mentioned, using a switch to turn on the relay power feeds for banks of fuses and relays.


Here is the link to the bussed fuse blocks and relay centers.

http://www.bussmann.com/library/news/RTMR.PDF

I installed these on the left and right side of the dash, facing the doors.

[DarkoNova]

Do you have pics of yours installed? This sounds like exactly what I need to clean up my spaghetti wiring, lol.

[68nate]

Not quite finished yet, but here are some pictures

[H2Ogbodies]

Hey Nate-nice pics. Are you planning on running a RS front end? That MSD box looks like it will interfere.

[68nate]

No, it's a firebird. I put the front bumper on to check clearance, it's pretty tight! I've got the rubber mounts behind the MSD box that I can shorten up if need be. I've got the starter solenoid and hi and low headlamp Power Relay Modules mounted on the passenger side front of the radiator support- doesn't leave much room for A/C lines. I have a gen II compac heat cool and defrost unit in it, but honestly I don't know if I'll ever hook up the AC. I guess I'll deal with that when the time comes. I'll post some more pictures tomorrow.

[68nate]

Here are some more pics of the headlamp Power Relay Modules installed. I'm protecting the charge wire to the battery through the non switched circuit of the high beam PRM on a 60 amp fuse vs. using a fusible link. Battery charge wire,fan PRM, and alternator feed are junctioned at the Power Fuse Module input on the drivers side engine side of radiator support. MSD box and Painless fuse panel are fused at the power fuse module. Fan PRM is controlled by a DPDT switch mounted on the dash- one position fan runs off the controller, other position shuts off power to the fan controller and PRM relay is energized to run fan at full speed. I'm setting up the H4 headlights so the outside two will be low beam, and all 4 will be on for high beam.

[DarkoNova]

Nate, what did you base the fuse size off of? I want to buy the relay module but it doesn't come with fuses. How do I know what size fuse I need? o_O

[68nate]

Ohm's Law-

So my headlights for example---- on high beam I'm running 4 h4 bulbs rated at 60 watts each and my battery is 12 volts

I (current) = P (watts) divided by E (voltage) 60 watts x 4 bulbs = 240 divided by 12 volts = 20 amps and then derate the fuse by 20% 20 amps x 1.2 = 24 amp fuse

So I'm running a 30 amp fuse on the high beam relay since it's the next fuse available after 20 in the J case fuses, you can get the j case fuses at any auto parts store.

For the fan relay fuses I'm just kind of going off of what others have tested for current draw on the Mark VIII fan. Mine is a single speed I bought from Jabin and I think he tested them at around 32 amps, so I'm going to start with a 40 and put my amp clamp on it and see what mine is actually pulling.

Hope this helps, not the easiest thing to explain typing on the computer

[grobb284]

Nate,
Thanks for the photos. Nice job on the wiring.

[67 455 Bird ragtop]

Nate - I like your setup. May "steal" your idea for my 67 vert. Any concerns about mounting your MSD box that far from your coil ???

[68nate]

Thanks! When I decided to put the MSD box where it is I tried to think of a reason why it should not be so far from the coil/distributor. I haven't been able to come up with a reason why it should be closer. The signal wire to the distributor from the MSD harness reaches fine, I did have to make the coil Pos. and Neg. wires a little longer if I remember correctly. It is very close to the bumber bracket, but shorter mounts could be used to cure this if needed.

[DarkoNova]

Ohm's Law-

So my headlights for example---- on high beam I'm running 4 h4 bulbs rated at 60 watts each and my battery is 12 volts

I (current) = P (watts) divided by E (voltage) 60 watts x 4 bulbs = 240 divided by 12 volts = 20 amps and then derate the fuse by 20% 20 amps x 1.2 = 24 amp fuse

So I'm running a 30 amp fuse on the high beam relay since it's the next fuse available after 20 in the J case fuses, you can get the j case fuses at any auto parts store.

For the fan relay fuses I'm just kind of going off of what others have tested for current draw on the Mark VIII fan. Mine is a single speed I bought from Jabin and I think he tested them at around 32 amps, so I'm going to start with a 40 and put my amp clamp on it and see what mine is actually pulling.

Hope this helps, not the easiest thing to explain typing on the computer

Hmm...well I was just going to get the PRM and hook up basically everything to them...

Although when I say "everything" I really only mean 3 gauges, an MSD coil, and a head unit. I really just wanted the PRM since it provided a constant 12v and a switched 12v in one unit.