New BDR RT4 Electrical Issues

RugbyRef · #1 (**permalink**) 07-07-2023, 07:31 AM

Quote:

Originally Posted by HighPlainsDrifter

Hi,
The temp should not rise to boiling! You should be able to drive with no fan on at 185 to 195*, put fan on when you slow down. I would replace the thermostat with a 180* one and burp all the air out of system. As for the fan, turn on fan and put a kleenex in front of rad and see if the fan is pulling air through rad or if they wired it reverse. try a 40 amp fuse as the amperage will spike when turned on.
Perry
PS; if the fan is blowing air forward instead of through rad the fan motor will labor in the wind and cause higher amperage draw and blow the fuse.

Thanks. The fan (one single fan) in my car is installed on the engine compartment-side of the radiator. The fan is pulling air and confirmed this by simply using a small microfiber towel to check air flow direction. The fan is directing the air correctly. Replaced the fan switch (thermistor) with an "upgraded" version as recommended by BDR. That didn't work. Jumpered the wires to the fan switch and the fan ran all day...WITHOUT the engine on. Once I started the motor, and the engine got up to normal operating temp, the fan circuit fuse will blow consistently.

With regards to putting a 40A fuse in vice 30A...never a good idea. The fuse is blowing for a reason not related to the amount of amperage running through the system. BDR tells me it is a 30A circuit and I measured it as such. The problem of the fuse blowing appears to happen when it gets to operating temp. Makes me think it is heat related...somehow?

HighPlainsDrifter · #2 (**permalink**) 07-07-2023, 10:32 AM

Well the only difference is the alternator, the rectifier may not be giving a good DC voltage- AC still present?
Good Luck.

Tom Wells · #3 (**permalink**) 07-07-2023, 10:34 AM

Rugby,

Don't know anything about BDR or its wiring.

Having said that, logic tells me there's a possibility that the thermal switch is wired incorrectly.

Here's why: you replaced the thermal switch so that should eliminate the switch itself.

Then, the fuse blows when operating temp is reached, which is when the thermal switch should activate.

If that does happen, it seems possible that the thermal switch is connected to a ground and not to the fan so when operating temp is reached, the thermal switch may short the 12V feed to ground instead of to the fan?

My SWAG for the day,

Tom

PS: On my cars the thermal switch is connected not to the fan, but to a relay. So the thermal switches I have do in fact ground the 12V signal through the relay, not the fan itself. No idea if yours is supposed to be done that way or not.

patrickt · #4 (**permalink**) 07-07-2023, 10:48 AM

Quote:

Originally Posted by RugbyRef

The problem of the fuse blowing appears to happen when it gets to operating temp. Makes me think it is heat related...somehow?

Your fan motor is an inductive load, not a resistive load. What that means is that, unlike a light bulb on a dimmer switch, it will draw more and more current as the resistance from a poor connection increases, because of heat and add to that the "load" of the heat on the fan blades that will also increase the amperage. So, on a cool day in your garage when you're testing it that fan might draw 10 amps using your inductive ammeter to measure it. But, when the under hood temperatures get really hot, and the wiring connections get really hot, and the air that the fan is trying to move gets really hot, and your voltage drops down, your inductive load will suck more juice, thus higher amperage levels. The only way you can be absolutely positively sure how much amperage that fan is drawing under load is to have a reliable inductive amp gauge on it and watch it when it's under a load that has blown the fuse in the past, or if you spring for a gauge that has high amp memory recall you can just check to see what the high number was. I've seen guys at my local club duct tape their iPhone under the hood to videotape a gauge during a really hot run, but a cheap bluetooth camera is probably a better idea.

RugbyRef · #5 (**permalink**) 07-10-2023, 08:15 AM

Quote:

Originally Posted by patrickt

Your fan motor is an inductive load, not a resistive load. What that means is that, unlike a light bulb on a dimmer switch, it will draw more and more current as the resistance from a poor connection increases, because of heat and add to that the "load" of the heat on the fan blades that will also increase the amperage. So, on a cool day in your garage when you're testing it that fan might draw 10 amps using your inductive ammeter to measure it. But, when the under hood temperatures get really hot, and the wiring connections get really hot, and the air that the fan is trying to move gets really hot, and your voltage drops down, your inductive load will suck more juice, thus higher amperage levels. The only way you can be absolutely positively sure how much amperage that fan is drawing under load is to have a reliable inductive amp gauge on it and watch it when it's under a load that has blown the fuse in the past, or if you spring for a gauge that has high amp memory recall you can just check to see what the high number was. I've seen guys at my local club duct tape their iPhone under the hood to videotape a gauge during a really hot run, but a cheap bluetooth camera is probably a better idea.

Excellent information...thank you!