It has been well documented here on the Hamb that I am not a fan (excuse the pun) of electric fans. But,the '32 Sedan I recently purchased has one and I need to ask you guys that prefer the electric fan if you have experienced this problem. I drove the sedan several miles today and noticed that when the fan came on the volts dropped from 14 to about 12....and stayed there. Is this normal? HRP
How's the health of the electrical system overall? Also, side-note, I'm reminded of either a blog here or an older tech thread using vintage fan covers, like off a Hunter desk or window fan, to dress up electric fans. Not sure if it would fit in this particular car though, but I figured I'd mention it. You probably remember what I'm referring to.
Nope. Well you may notice that the needle wiggles a little bit but it should not drop your volts unless your alt is not up to par or it isn't wired properly or both. When I am running electric ( which is common) I pull my hot to the relay as short as possible and either from the battery or the starter. Normally I use 10 gauge wire for my line ( hot). The other wires don't need to be too heavy as all they do is trip the relay.
I would test the alternators output and the batteries capacity and health. After that take a look at how the fan was wired in, relays fan draw etc. The car having sat for a while it could be any number of things. Or Danny, you could just pull the whole thing out and install one of your favorite mechanical fans that you have posted so many pictures of
The car has a new battery. Beeno,the needle moves a little,I flipped the switch off and the needle moves back close to the 14 volts. HRP
I would probably have to mail him one I'll just about bet he has used his entire stash of mechanical fans.
It should just tickle the gauge down when fan comes on then the alternator kicks in and boosts it back up. That's what's supposed to happen. It could be a bunch of stuff. If your going to gauge your expectations on the gauge reading, the gauge needs to be verified and that its wired into the correct place. ^^^ that's first thing^^^ If you don't do that just completely ignore the thing instead of partially ignoring its verification. Then methodically go thru the fan circuits and alt out puts.
Larry,if this thing leaves me on the side of the road I'm not beyond doing that. I figured that so many members here praise their electric fans I might leave it in the car,after all,it is a street rod! but only if I don't end up going somewhere and having a dead battery when I am ready to leave. HRP
Danny if it runs after shut down you need to rewire it so that it shuts off when you shut the car off. I always use switched power to the relay. I don't know that I praise or don't praise electric fans I am just lazy most of the time and if a mechanical fan is going to be a pain I use an electric. Oh and watch for dirt daubers, they can build a nest overnight that will block the fan and then it won't work. Uh ask me how I know.
Beeno,I need to correct a misunderstanding,there is no relay. It just has a on and off switch and I noticed the temperature was approaching 220 and not being use to the car I realize the fan wasn't on. HRP
You need a relay less then 20 bucks from summit and it comes with instructions. You will probably be in 30 bucks if you buy a tem sender and if you do get the one that screws into the intake or head and not the one that goes in the radiator hose.
Sounds like a voltage drop problem. Being a motor, if voltage goes down, current goes up. I'm not a big fan of relays, but if this has the typical street rod wiring harness in it, a relay is called for. Wire the fan (using at least #10 wire) directly to a 12V source as close to the battery as you can get (with an inline fuse) and control it with the relay (using your existing switch if you want). DON'T pull power out of the fuse panel, as inadequate wiring (for the load) to the panel is very likely the reason for the low voltmeter readings.
HRP. My coupe running a near new cooling components fan did the same thing. Some of the difference is the gauge I'm sure. But with the fan on the ac on and the headlights it pulled the volt meter hard. Never below 12 but not the normal 13.5. My local starter alternator guy say my alternator is working fine. The instructions in the cooling components units tell us to use a 70 amp relay. That's a good draw on start up. I would use a relay. Just my thought.
Check out the troubleshootting guide I posted a little bit ago. A thorough understanding of the system is paramount to troubleshooting a problem, so if you don't have a schematic of the circuit, it's time to trace it out on paper. I do a lot of electronics repair, and if I can't find a copy of a schematic somewhere, I trace it out myself. It can be a pain in the butt, but by the time I trace it all out I have a very good understanding of the circuit, it makes diagnosis of the problem far easier.
A relay is not going to change the amp draw of the cooling fan. A relay will keep the direct power from having to travel through the switch. What is the output of the alternator? If you have a low output alternator (35-45)then it will show low on the gauge with a 30 amp draw from the cooling fan......put a 100 amp alternator on it and the gauge should not even quiver when the fan is on....
I had a 77 camaro winter beater/parts car that would do the same shit when I turned on the heater fan. It was wired to the fuse panel [see Crazy Steve's post] and although it appeared the voltage was low, it never showed hard starting or low batter voltage symptoms. The guys are correct to recommend using a relay to power up that fan. It may save you from putting out a fire in the car.
Talk to your buddy. Is this something he was used to seeing? Sometimes those gauges do funky things. I have one in an OT car that flickers low like that when the stupid turn signal is on. Freaked me out the first time I ever saw it but its never been a problem, other than aggravating me. I agree with the others, I'd want a relay to keep all the current from running through the switch. You can usually find the little ice-cube ones at the u-pull-it. They have a standard set=up for the contacts and the coil. I dont remember what it is, but a search should bring it up. I think I would want a temp switch to cut the fan on if you forget. You can use the same type that they use to turn on an idiot light, just wire it in parallel with the switch you have already, if you have a relay. Good Luck
Where is your gauge measuring voltage from? Put a voltmeter at your battery if it reads 12 volts with the fan running you need to take action, if it reads 13.5 or 14.5 you are good to go.
In order to avoid taking a class (Electric 1) look up 'electrical relays' on line... No electric D.C. motor should be run without a relay. All cars in current production (no pun intended) use relays for lighting, electronics, and electric motors. The amperage draw of an electric fan motor is extreme, so use a relay. (duh)
I'll disagree with that statement. There's plenty of motors in an average vehicle that don't use relays; wiper motors, window motors, heater blower motors to name three. If the wiring in the circuit path and the switch are rated for the load, you don't need a relay. In most cases, a relay is simply a 'fix' to correct a inadequacy in the circuit path. The fact that any inadequacy that may exist could be either from poor design or as a cost-saving measure is immaterial. The proliferation of relays on new cars isn't so much that relays are required for the loads as it's cheaper for the manufacturers to use relatively inexpensive relays instead of upgrading the wiring harness and/or control switching to carry the loads involved.
Look up 'Wiper Relay'. Google it. (for an unnecessary or 'non existent' part, I sure have replaced a number of them in my years in the trade.) Maybe they only have 'em in California? They all have 'em. To deny that is just....well, Crazy, Steve. There's a good article on Watson's Street Rod Works' site. Just click on the first subject in his list: "A Current Topic". To deny the facts is sure to break Ohm's Law!
Not a valid comparison. Go look at any 50s, 60s, and probably most 70s cars and tell me how many wiper relays you find. In fact, tell me how many relays of any kind you find. Relays were a relative rarity on cars (except for horn relays and 'starter solenoids') until the major use of electronics started in the late 70s. In this particular case you're noting, a wiper relay is needed because they moved the wiper controls out of the dash in most cases onto the turn signal lever. Space constraints limits how big the controls can be, so small, light-duty contacts are used. These contacts are too small to carry the motor load reliably, so the actual motor load switching is moved to a relay. All a relay is is a switch; whether it's operated manually or electrically, it's still just a switch.
and newer O/T cars ( we will not get into semis as they have everything thru a relay ) they do not use a typical relay either , the bcms ( body control modules ) have several of them ( micros) in the cases and if one fails you often have to send the BCM back to a manufacturer or repair station to get it fixed . many cars since the 1970s have been using more and more relays . the camaro that rocky had had a relay for the high side of the blower motor as it was connected directly to the back of the alternator by GM . many a 70's gm vehicle I fixed that had a dead heater motor often it was the resistor pack and relay burned up . I agree with PNB on the relay to the fan comment , seen several looms that come in that the main lead was melted and some wiring smoked from just adding a fan and taxing the system , when ever I wire in a electric fan its a low amp control circuit that goes to the relay and the fan supply power comes from the battery direct .
Tried a relay a long time ago. It burnt up. From there on I bought an expensive switch and wired four of them directly. One switch is operating two fans in my 37 flat headed ford. 15 yrs that way with a generator. Expect a small voltage drop but I agree it should return fairly quickly.
Most current fans eat up a lot of power (amps), just because of motor design. Give these a close look - http://www.deltapag.com/Technology.html One of the three reasons I bought this fan (two, 12") is because of the low amperage draw, brushless design... The other two reasons, because of the short depth and the "shaped" blades. The car isn't on the road yet so I can't verify these claims yet, but after two "long" phone calls to them as to the history and design, I felt fairly comfortable with the purchase. I also got a few thumbs up from guys here on this board when I asked about this fan company. Mike
I'm going to take the car to a pal that has a battery & alternator shop and let him check out the alternator,if that checks out I'll check an see if there is a relay or not. HRP
Exactly. The gauge might be dropping about 2 volts when the actual voltage only drops .5 volts. Unless you have too many accessories for the alt capacity, or a problem with the alt itself. Since you said the battery is new. Hopefully the fan is fused and isn't blowing a 25-30 amp fuse?
A lot of Street Rod fuse panels have a fan relay built into them. That switch could be turning on the relay. If there is no sensor in the system Centech and Dakota Digital have fan controllers that read off of your dash temperature gauge so you do not have to add a extra sender for the fan. They are both adjustable. You do need a minimal 100 amp alt for the electric fan and ac. Also if your ac system is R134 the electric fan should come on when the ac comp is engaged. Both controllers will do that also. Love the new car you are gonna get spoiled driving it. There is NO law that says you cant drive a comfortable Hot Rod. HAHA
The Jalopy Journal
