Electrical question
Thread Starter
Burning Brakes
Joined: Sep 2016
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From: McMinnville Oregon
Electrical question
I should know this but somehow it's not popping into this old mind.
The battery is new. The Hemi/Vette doesn't have a thermostat. So what they did was put in an electric fan behind the radiator with a kind of external thermostat in a water line that provides power to the fan at about 200 degrees. What I notice is the amp meter goes negative when the fan kicks in. The alternator has this number on it. It's a Delco Remey #1102385 55A. So I assume a 55 amp unit. Fan belt is tight and I wouldn't think an electric fan would be able to pull the alternator down. I can spin the fan easily by hand. Also when I turn on the headlights the amp meter stay zero or slightly positive.
My first thought was the battery because the other day I bumped the wire off the balance resistor and couldn't get it to start and could tell the battery was pulling down. When I checked I saw the battery was new. Then if I remember correctly the engine will actually run just on the alternator alone.
Anyone have an idea I'm missing??
KO
The battery is new. The Hemi/Vette doesn't have a thermostat. So what they did was put in an electric fan behind the radiator with a kind of external thermostat in a water line that provides power to the fan at about 200 degrees. What I notice is the amp meter goes negative when the fan kicks in. The alternator has this number on it. It's a Delco Remey #1102385 55A. So I assume a 55 amp unit. Fan belt is tight and I wouldn't think an electric fan would be able to pull the alternator down. I can spin the fan easily by hand. Also when I turn on the headlights the amp meter stay zero or slightly positive.
My first thought was the battery because the other day I bumped the wire off the balance resistor and couldn't get it to start and could tell the battery was pulling down. When I checked I saw the battery was new. Then if I remember correctly the engine will actually run just on the alternator alone.
Anyone have an idea I'm missing??
KO
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How many amps does the fan draw (usually 30 or 40). Also, does it initially go farther - and then come back a bit? Electric motors draw the most current as they come up to speed. But consider this, with stock headlights and the high beams on you draw less than 20 amps. Add in the other lights and electrical load and you are already at about 80% of your alternators capacity. Electric fans that are effective usually draw around 30 amps. Add it up and your alternator is under powered.
Thread Starter
Burning Brakes
Joined: Sep 2016
Posts: 946
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From: McMinnville Oregon
The fan is very light weight plastic and it was installed by the previous owner. You can spin it with just a touch so it shouldn't need much current to turn it.
Two little wires on the thermostat. One obviously from a power source, I don't know where, and the other to the fan. I don't think they could carry 30+ amps.
The amp meter goes to about 2-3 needle width's negative with the fan running.
Two little wires on the thermostat. One obviously from a power source, I don't know where, and the other to the fan. I don't think they could carry 30+ amps.
The amp meter goes to about 2-3 needle width's negative with the fan running.
Team Owner
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From: Kannapolis NC
The fan is very light weight plastic and it was installed by the previous owner. You can spin it with just a touch so it shouldn't need much current to turn it.
Two little wires on the thermostat. One obviously from a power source, I don't know where, and the other to the fan. I don't think they could carry 30+ amps.
The amp meter goes to about 2-3 needle width's negative with the fan running.
Two little wires on the thermostat. One obviously from a power source, I don't know where, and the other to the fan. I don't think they could carry 30+ amps.
The amp meter goes to about 2-3 needle width's negative with the fan running.
Last edited by 65GGvert; Oct 5, 2018 at 02:43 PM.
Pro
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From: Myrtle Beach South Carolina
It doesn't matter how easily the fan spins when moved by hand. The fan is moving air when running, that is what is known as the load the motor is working against. It sounds like the fan motor is doing it's job.
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Army
The reason I asked the "hook up" question above (and 65GGVert knows where I was heading) is that the ammeter output requirements are controlled by the voltage regulator and indicated by an especially small drop in potential between two points....enough so that the resistance in a wire run to power something straight off the battery can create erroneous ammeter indications. This is called "remote sensing".
A better place for power take off for accessories is off the horn relay bus...
A better place for power take off for accessories is off the horn relay bus...
Thread Starter
Burning Brakes
Joined: Sep 2016
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From: McMinnville Oregon
I'm going to do some continuity checks on the wires going to the thermostat switch, maybe I can tell where the power comes from. Then I'm going to check the voltage at that switch when the fan's running. Maybe the load of the fan is pulling down the voltage out of the alternator.
When you say powering straight off the battery do you mean the battery bus as in the alternator or starter?
Access to the battery with this big engine was addressed by moving the battery to the storage area behind the drivers seat, I would have put it on the passengers side for a street application but maybe they were used to the body torquing to the right on a drag race start.
When you say powering straight off the battery do you mean the battery bus as in the alternator or starter?
Access to the battery with this big engine was addressed by moving the battery to the storage area behind the drivers seat, I would have put it on the passengers side for a street application but maybe they were used to the body torquing to the right on a drag race start.
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Army
I'm going to do some continuity checks on the wires going to the thermostat switch, maybe I can tell where the power comes from. Then I'm going to check the voltage at that switch when the fan's running. Maybe the load of the fan is pulling down the voltage out of the alternator.
When you say powering straight off the battery do you mean the battery bus as in the alternator or starter?
Access to the battery with this big engine was addressed by moving the battery to the storage area behind the drivers seat, I would have put it on the passengers side for a street application but maybe they were used to the body torquing to the right on a drag race start.
When you say powering straight off the battery do you mean the battery bus as in the alternator or starter?
Access to the battery with this big engine was addressed by moving the battery to the storage area behind the drivers seat, I would have put it on the passengers side for a street application but maybe they were used to the body torquing to the right on a drag race start.
You could disconnect the power at the device (fan ?) and temporarily connect a jumper from the device to the horn relay buss to see how the alternator reads....
Last edited by Frankie the Fink; Oct 5, 2018 at 06:42 PM.
Thread Starter
Burning Brakes
Joined: Sep 2016
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From: McMinnville Oregon
Frankie
Slowly catching back up with this old Vette. You mentioned the horn relay. The wires are about 16 gage and power comes from a small plastic relay with Bosch on the top underneath a metal relay with Delco Remey on it located in the picture just to the right of the radiator.
With just the key on I have 12.5 volts at the thermostat switch, with the engine running and the fan running it's about 11.5. I wonder if the wire size isn't enough for the fan load?
Slowly catching back up with this old Vette. You mentioned the horn relay. The wires are about 16 gage and power comes from a small plastic relay with Bosch on the top underneath a metal relay with Delco Remey on it located in the picture just to the right of the radiator.
With just the key on I have 12.5 volts at the thermostat switch, with the engine running and the fan running it's about 11.5. I wonder if the wire size isn't enough for the fan load?
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Army
The horn relay itself is not involved in what I suggested....the contact buss it sits on is a major power distribution point and very close to the point required for proper 'remote sensing'.... If you connect to that and run the fan (and engine) briefly and see if your ammeter acts normally. You'll have to either decide to leave the connection where it was and put up with the gauge reading or maybe beef up the wiring to handle the fan... I don't know what the fan is rated at current-wise so I can't say if the existing wires are sufficient..
Last edited by Frankie the Fink; Oct 6, 2018 at 05:14 PM.
Thread Starter
Burning Brakes
Joined: Sep 2016
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From: McMinnville Oregon
It's not a issue unless it's warm and the fan comes on. Think I'll run the fan a see if the wires get warm. That will give me an idea about the current requirements for the fan.
I'm tinkering with the main jet size in the AFB's and then have to pull the harmonic balancer as the rubber has deteriorated and I can move it by hand. Will send it out to be rebuilt.
My porsche I've had for 20 years just sits on the lift and smiles as I tinker with first the Mini, then the Vette. When I come back from a short test drive and open the hood the Porsche knows when I get p****d I'll take her out and come back with a big smile as everything works perfect.
I'm tinkering with the main jet size in the AFB's and then have to pull the harmonic balancer as the rubber has deteriorated and I can move it by hand. Will send it out to be rebuilt.
My porsche I've had for 20 years just sits on the lift and smiles as I tinker with first the Mini, then the Vette. When I come back from a short test drive and open the hood the Porsche knows when I get p****d I'll take her out and come back with a big smile as everything works perfect.
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Just because your alternator is marked 55A does not mean that is what it is currently built to put out. Most of the rebuilt unit from the parts houses were rebuilt to output 61 A or 63 A (can't recall which).
Take your alternator to a good local alternator rebuilder and let him tell you what it is doing.
When the resto shop added an thermostatically controlled electric fan to my 64 during the restoration, they upgraded the alternator to a 100 A system (Powermaster Street Master Alternator)
Take your alternator to a good local alternator rebuilder and let him tell you what it is doing.
When the resto shop added an thermostatically controlled electric fan to my 64 during the restoration, they upgraded the alternator to a 100 A system (Powermaster Street Master Alternator)