I've read that the Volvo relay is rated at 60 amps.....and it makes sense if Volvo factored in the start up spike. But why put 10 awg wire on a 60 amp rated relay?
I've also read that this xr7 (thunderbird) fan is a Taurus fan motor with mark Viii blades. If it pulls the same as the Taurus fan then it's fine. If it is the same motor....it's dealing with bigger blades and more air than the Taurus fan does and therefore drawing more amps. It's not the amps or air draw the mark 7 has so it won't be as hard on the system. It does however have bigger 8 awg wires. And those wires don't match the 10 awg wires on the relay. I think the relay actually had a 30 amp breaker. The Taurus fan does....or it's a 30 amp slow fuse.
The things throwing me off is the wires going to that fan are bigger than the wires to the relay and the actual relays rating.
I know for a fact it's rated for at least 30 amps.....if it will run this fan then I want to run it.
The 10awg wire in such a short distance is rated for 40amps.
The mark 7 fan runs at 40 amps. It spikes higher but wire size won't matter for the spike. I believe it's too fast to put the wire under too much stress. It's the relay that takes all the punishment.
I can hook it up to a batter charger and watch the amp draw of it. Being it's a xr7 and is not the mark 7 fan. The amps would be less.
I don't understand voltage drop and resistance......I don't know what the original specs are.
Meaning......if I hook this up with a good alternator, will it see 14.4 volts? What drop is acceptable. This is beyond what I know electrically. I would rather understand voltage drop over a wire or system that is too small than throw parts at this thing. I don't want to get a 90 amp relay when a 70 will do or get a 70 amp relay when a 30 will do. I'm at the point where I want to know how to gauge and measure this so I can solve the problem and engineer the system according to what I have to deal with.
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The Mark VIII is a bigger motor and draws more amps but I have yet to see anything above 45 amps even on an old fan when it’s running. It does have a momentary spike but again I have yet to see the 100 amps I hear about.
Our testing showed the Mark VIII fan ran 26-28 amps on low, with a 37-40 amp startup spike. On high it had a draw of about 32-35 amps with a 48-53 amp startup spike. This is tested with our relay kit wired with the step through configuration and a new fan. A startup from dead stop to high speed will draw higher amps.
The Taurus fan ran 24-26 amps on low, with a 32 amp startup spike
Then on high it used about 28-29 amps with a 40-45 amp startup spike. Again wired with our relay kit and a new fan.
With this information.....the Volvo relay would easily run the Taurus fan.....and it would run the mark7 fan but the specs are close and the words would have to be under 5 feet. My RF24 fan doesn't flow as much air as the mark7
with that much amp load from the fan... i am so glad you are going to make it intermittent operation.. but you are also going to need to look at alternators perhaps in the 120 amp range..
this is a voltage drop test i perform on each car.. print a copy or two.. pickup your hand held digital volt meter and do your daily driver.. do all your daily drivers.. this is practice for the real thing.. and you may find small issues that a few minutes will solve problems.
http://i.imgur.com/WMDprhm.jpg
voltage drop is checking for kinks in your garden hose..
kinks in your garden hose only give you issues when you are watering the plants... there won't be enough flow because of the restriction/kink..
with the kink in the hose... with the nozzle closed.. there will be equal pressure at both ends of the hose..
with the nozzle open.. there will be less pressure at the nozzle.... this is what we are looking for with the voltage drop test... if there is a kink/Restriction/Resistance there will be slightly less voltage at the end of the wire... how much less is why we perform the voltage drop test.. copper wire has resistance... 2/100th or 4/100ths of a volt is kinda what normal lower current accessories should be.. higher load components like on test 6 alternator to battery will have more current flowing and more voltage drop..
testing between the positive battery post and the positive wire connections at the fan let you know if there is too much voltage drop in that circuit.. you can actually calculate how much current is lost..
testing between the negative electrical connection at the fan and the negative battery post will let you know if you have a good connection.
why is there 8 gauge wire in the factory ford wiring.. it allows more electron flow.. less resistance. less voltage drop.. and faster fan rotation..
70 amp relays can be had... for probably 15 bucks each.. they use larger electrical connections for the 30/87 connections ..
doing the volvo relay.. is really interesting as it prevents both power wires to the fan from being active at the same time..
i have a CRAZY stupid idea... as usual... use the volvo relay.. to control a pair of 70 amp relays... that have 8 gauge wire to the 30/87 connectors. you will at that point have a BULLET PROOF fan control system ..
i am just heading out now.. the volvo relay will probably operate the fan just fine... the professionals in us are thinking of how ford did it with 8 gauge wire and the 10 gauge or what ever it is might get hot.
let me post a wiring diagram of a ford Constant current relay module.. i am NOT saying to run one of these.. they are complex and like to blow out..
maybe i am totally wrong... go with the 30 or 40 amp relays... go with the volvo relay.. the ford CCRM uses single 40 amp relays but double connections at the CCRM connector.. so the current does not heat and melt the connector..