Electric Fan

timkins · May 11, 2005, 04:38:19 PM

I had to pull the Grill Shell off my 32 Sedan this past weekend and in doing it, I had to unplug the electricals to the lights and Electric Fan. When I just took the car around the block and turned on the electric fan, the water temp gauge ROSE instead of going down. I am running just an on/off dash mounted switch with no relay. I am guessing a bad ground on the circuit, could that be right?

Dave · May 11, 2005, 06:00:16 PM

Quote from: "timkins"I had to pull the Grill Shell off my 32 Sedan this past weekend and in doing it, I had to unplug the electricals to the lights and Electric Fan. When I just took the car around the block and turned on the electric fan, the water temp gauge ROSE instead of going down. I am running just an on/off dash mounted switch with no relay. I am guessing a bad ground on the circuit, could that be right?

Did you hook it up backwards and its pushing instead of pulling?
Dave

timkins · May 11, 2005, 06:38:29 PM

I am sure it is hooked up correctly as I checked the flow of air when it was running.

Okiedokie · May 12, 2005, 08:59:48 AM

Are you sure the fan is running? Sure you didn't pop a fuse?

timkins · May 12, 2005, 11:05:33 AM

I am positive the fan is running. I turned the ignition on and turned the switch on and checked for airflow. It was pulling air thru the radiator and exiting in the engine bay. This morning I installed a relay in the electrical system for the fan, lets see if that makes a difference.

Okiedokie · May 12, 2005, 11:38:18 AM

It would seem that if it worked ok previously, and you know it is sucking thru the radiator, the most likely culprit will be electrical connections. Poor ground, wire loosing contact due to engine movement, or such.

HOTRODSRJ · May 12, 2005, 09:59:05 PM

Quote from: "timkins"This morning I installed a relay in the electrical system for the fan, lets see if that makes a difference.

Good plan could be the problem? Most electric fans pull at least 10 amps or more and most switch contacts are NOT rated for that kind of continuous action. Therefore sometimes the switch will begin to fail and increase the resistance of the contact (which woud make the switch very hot) and provide a voltage drop at the switch slowing the fan.

timkins · May 13, 2005, 08:22:57 AM

Well I took the car for a ride last night with the new relay installed. At cruising speed the fan does not make the temp on the gauge rise like it did previously BUT at a stop and idle there is a noticeable increase in the temperature on the gauge. I borrowed an infra red sensor gun and I am going to check it over the weekend to see if it really is increasing at an idle.

HOTRODSRJ · May 13, 2005, 09:05:32 AM

Quote from: "timkins"Well I took the car for a ride last night with the new relay installed. At cruising speed the fan does not make the temp on the gauge rise like it did previously BUT at a stop and idle there is a noticeable increase in the temperature on the gauge. I borrowed an infra red sensor gun and I am going to check it over the weekend to see if it really is increasing at an idle.

How large of fan do you have on your ride? What kind of amperage is the fan drawing? If's it's not a Spal or Derale 16" top of the line fan, there is some doubt as to the overall CFM capabilities usually. Lot's of "pretenders" out there pushing "2700cfm" fans that only draw 11amps. Simply put, impossible to do with that amout of watts, even with the best fan/shroud system.

So, I am familar with the 32 radiators and how they should mount and work. You will need at least a 16" fan with at least 20amps (or about 260watts) of power to provide enough airflow at idle to adequately cool the most modest small block.

Leon · May 14, 2005, 03:38:21 AM

On Power Tour 2001 I thought my 23 was running hot all the time but part way through the run my headlight switch started giving me problems (I always ran with the lights on) so I had to turn them off. The instant I did, the gauge went down. Turn them back on, it went up. When I got home I ran a separate larger ground from the gauges to the engine block and never had the problem again.

Bruce Dorsi · May 14, 2005, 07:39:56 AM

Quote from: "Leon"On Power Tour 2001 I thought my 23 was running hot all the time but part way through the run my headlight switch started giving me problems (I always ran with the lights on) so I had to turn them off. The instant I did, the gauge went down. Turn them back on, it went up. When I got home I ran a separate larger ground from the gauges to the engine block and never had the problem again.

Thanks, Leon! ....That's a good point to remember for future use!

Most people fail to understand the need for large, reliable grounds, especially with fiberglass bodies.
More often, a bunch of grounds are run to a common terminal, then grounded with one similar-sized conductor. ....The ground wire should be large enough to handle the TOTAL currents of ALL components using that ground path.

timkins · May 14, 2005, 09:09:01 AM

The latest on the electric fan. I took the car out again last night and at a red light I turned the fan on and the temp gauge rose slightly BUT after leaving the light the temp went down significantly and seemed to stay down.
To answer some of the questions, the motor is a stock 78 2 bolt 350 truck motor that may(?) have been bored .030 for rebuilding. The fan is a 16" Derale and I am not sure what the amperage draw is yet. I did have a previous problem with the gauges that when I turned the lights on ALL of the gauges went down IE; oil pressure to zero, gas about 1/2 tank etc. I thought I fixed that problem by running a better ground to the gauges but I will revisit the ground and run a larger one to the engine block. I let you know how I make out.

HOTRODSRJ · May 14, 2005, 10:54:32 AM

Quote from: "timkins"The latest on the electric fan. I took the car out again last night and at a red light I turned the fan on and the temp gauge rose slightly BUT after leaving the light the temp went down significantly and seemed to staye down. I did have a previous problem with the gauges that when I turned the lights on ALL of the gauges went down IE; oil pressure to zero, gas about 1/2 tank etc. I thought I fixed that problem by running a better ground to the gauges but I will revisit the ground and run a larger one to the engine block. I let you know how I make out.

First, the radiator becomes more efficient when you are moving therefore WILL be cooler as indicated. Fan running probably does not have anything to do with it during cruise.

SEcondly, gauges that are affected by turning the other electrical features on or off is usually a voltage drop problem from the battery/alternator bus to the fuse box. The increase load drops the voltage at the reference terminal of the gauges and skews the readings.

Grounds could be an issue as indicated, but my money is that you see a significant voltage drop at the gauge reference feed when all this apparatus is turned on.

timkins · May 14, 2005, 12:30:06 PM

I just finished running the gauge ground to the block of the car and it made a difference. Now when I turn the fan on there is no fluctuation in the temperature gauge also when I turn on anything electrical, I do not get the drop in the voltage gauge that I was experiencing prior to running the ground to the block. Thanks to all for their suggestions and previous experiences.

HOTRODSRJ · May 14, 2005, 02:39:02 PM

Quote from: "timkins"I just finished running the gauge ground to the block of the car and it made a difference. Now when I turn the fan on there is no fluctuation in the temperature gauge also when I turn on anything electrical, I do not get the drop in the voltage gauge that I was experiencing prior to running the ground to the block. Thanks to all for their suggestions and previous experiences.

While your gauge ground is important, I would submit that your engine ground or chassis groud is suspect too? You should be able to ground your gauges to "chassis" ground with no problems. But, if your engine is not sufficiently grounded then all bets are off. Your engine ground should be at least a 4ga to chassis to battery neg. or visa versa. This assures you of a good ground all the way around.