Well, I got a new switch. This one is 190 degrees on and 175 degrees off vice the last one which was 180 degrees on and I-don't-know-what degrees off. Per the temperature gauge, the switch closed (fans came on) at about the temperature advertised. I could detect neither a decrease nor an increase in temperature while the fans were on. Three minutes after starting, the fans shut off. Just as they did with the last switch.

Assuming I didn't get two bad switches that failed in the same non-standard way (intermittent), what might I focus on next?

 

Can you post a video of the fans running? And does each fan have a relay? My dual Spals pull nearly 15 Amps each. Perhaps your fans aren't up to the task, or aren't seeing full voltage due to the way they are connected.

 

After you fix you fan problem, please fix your fuel line next.

 

@Bikespace mentioned a couped of items:

• A video of the fans running: I could, but without knowing what one might be looking for, I'm not sure it would be that useful. I'd hate to waste y'all's time by shooting the wrong actions.
• Does each fan have a relay: There are two relays wired into the system. Each fan appears to be rated at 12 V and 80 watts.
• "The system" may be the source of the problem.
  • It appears, but I can't confirm, that both relays use the same wire to go from their 30-position to the 30-amp circuit breaker.
  • The wire from the circuit breaker does not go directly to the battery side of the alternator. It goes to a "clump" of wires, and then a wire comes out of this "clump" to the alternator.
  • The "clump" of wires appears to be associated with the head/parking/side marker lights.
  • Wiring from a third relay associated with the A/C system sneaks in there as well.
  • However, only one wire reaches the battery side of the alternator.
  • There's a lot of merging of wires. This may be appropriate or not.

At this point, I'm running with the idea that the circuit breaker is seeing a problem and cutting off power. Then at some point, it stops seeing a problem and connects power again but for a shorter time. Although I'm not operating the lights or the A/C, more could be going on than I'm aware of. Ideas?

@Crimson Thunder advises to take care of that mess of a fuel line system. Amen to that. @Kie has a set up that's pretty clean (you can see it in pictures above) but I don't know where the fuel filter would be. The main reason I have this mess is that my fuel system didn't have a fuel filter. A future me will have to find a better way.

Apologize is this is the second post with essentially the same information. My last post didn't show on my end after a few hours, so I figured it didn't go through.

 

In my opinion, do NOT ditch the electric fans yet. That system should work very well. I would suggest replacing the relays that turn on and off the fans first. That is an easy fix that will help.
if you have a power probe, I would:
1. Check the power going into the relay switch to determine whether it is getting the signal to turn on when the temp is high but it shuts off. That will tell you whether the problem is that they are getting switched off prior to the relay.
1.a (Bonus step) If you are using a power probe, and there is no power going to the relay, apply power and see if the fans come on. If so, you have a bad switch.
2. If power is going in, then check to see if there is power going to the fans. That will tell you if the relays are bad.
2.a Repeat bonus step. That will tell you if it is the relays for sure.
3. If the fans are getting power, but not spinning, the motors might be partially fried. At that point you could be confident that you will need to change the fans.

 

Circuit breaker?

Perhaps that is the issue. If those fans are up to snuff, they need heavy gauge wire to each relay, rate for 20 Amps each, minimum. Look for a diagram by @Richard454.

The "circuit breaker" in the headlight switch is a common issue. Perhaps that is what's going on here?

 

I noticed no one has asked the requisite dumb questions yet. Allow me!

This behavior is new.. correct? The fans used to stay on longer and properly cool the engine. Correct?

Have we confirmed the engine temp is actually creeping up? With one of those fancy phaser/laser pointer things aimed at the thermostat housing and set for probe.

Thank you op for noticing my fuel line. I learned quickly that any sort of rubber fuel delivery component in the engine bay of my C3 would result in the forum reigning down terror, misery and public shaming on a galactic level. I wasn’t ready for that so I had J2 Racing in Monroe whip up something for me. Its very chic and appears leak proof. There is a fancy inline billet alloy filter down low that comes apart for cleaning.

 

I run a duel temp switch w/2 relays and fuses,First fan on 185 then other at 195 if one goes down you still have one working fan.IMO dont wire them together

 

Member Responses
@scottjamison

• I tested both relays by applying power (I used a battery charger) across positions 85 and 86. I then tested for resistance across positions 30 and 87. I got the "clicks" for the first test, and there was no resistance for the second. Does that go far enough?
• I don't know what a power probe is unless, maybe, it can go by another name.
• If by switch, you mean the temperature switch, I have replaced it since starting this thread. The fans shut off in the same manner as with the previous switch.
• I have not tested the fans. Yet. The regularity with which they come on and off does not lend me to believe they are going bad.

@Bikespace

• The circuit breaker is where I left off this evening. I have concerns with the one that (I assume) came with the fan-wiring package. This caused me to look at the car's 30-amp circuit breaker in the fuse box. Still trying to figure out how I'm gonna get two hands, two probes, and line-of-sight in order to test the box for the circuit breaker. More on the after-market circuit breaker below. Suggestions?

@Kie

• New behavior? I don't know. I've had this car for over a year and a half, and I only now have been able to drive it enough to determine that the fans aren't doing their job. This just happened to be the next biggest issue.
• I do have an IR temperature sensor, but I haven't figured out the surface refraction/reflection (if either of those is correct) adjustments. However, when the dashboard gauge indicated that it was getting near 260 degrees, the cooling system audibly agreed. Additionally, the temperature gauge was in alignment with the first and second temperature switches (one being a 180 degree on and one being a 190 degree on). Well, as much as the dash gauge could agree.

@gjohnson

• I like the idea on the surface. I'm nowhere near educated enough to tackle that one. Let me attempt the basics first.

What I've Done

• As far as wiring goes, it's not pretty with respect to the fan relays (two of them), the A/C relay, some native headlight wiring, and the alternator.
• I spent some time trying to figure out what the wiring should be like (i.e., what should be connected to what). I came up with something that I "think" is correct.
• Then I spent some time trying to map out what is actually going on.
• Spoiler Alert: they don't match.
• Main Differences:
  • My diagram allows for a jumper wire between the two 85 positions of the fan relays, as well as the 86 positions. In reality, the 85 positions of one relay are tied into the 86 positions of the other relay. One pair goes to the temperature switch. The other heads back towards the cabin. I'm hoping that's ignition.
  • My diagram has battery power (alternator) going to the circuit breaker and then on to the 30/87 positions of the relays before heading on to the fans. In reality, battery power goes into a wire bundle heading back towards the cabin. A wire coming from the cabin direction goes to the circuit breaker. These two items are what make me think I need to check the vehicle's circuit breaker.
  • My diagram assumed that I had a trinary switch associated with the A/C. One, whatever I thought was a trinary switch isn't. Two, the A/C relay is wired directly to the A/C compressor/clutch. There is a switch but it's two-prong. Maybe a binary switch?
• There's some "stuff" going on under the dashboard. All the electronic extras that have been added by folks over the years have merged there. Not a label to be had.

What I'd Like to Do

• Test the vehicle's circuit breaker.
• Route power from the battery (alternator) to the fans as described above with its own dedicated circuit breaker. It would mean adding a circuit breaker without knowing what is using the current one aside from the fans (if the fans are actually "seeing" the circuit breaker). The goal would be to remove the "extra" one in the future.

Thoughts?

 

OK. I'll pipe up here. I put electric fans in my 77 back about 20 years ago. I'm pretty sure I made every mistake possible. I wasn't on this forum then. Don't think I had much grasp of the internet then. Which was new 20 years ago.
Anyway, let's cut to the chase. I learnt a lot.
let me share.
First, the NUMBER 1 reason my early efforts on getting reliable electric fans stemed from the fact I had little knowledge of just how many amps these things pull. And I purchased a wiring kit from Summit that I thought would work.
Silly me.
One thing to keep in mind. Circuit breakers work by a bimetel spring that heats up and "pops". The engine compartment heat in a C3 kinda loads the breaker if you know what I mean.
So.
Start over. Pull your power off the starter solenoid where your main positive battery cable connects. Install a slow burn FUSE just a couple inches from this power pick-up. Use HUGE wire. You can't overkill the wire size. Now run this power wire to 2 30 amp relays, one for each fan, or one 60 amp relay. Run huge size wire from the relay to the fans. Run a huge size wire from the fans to a good ground. The wire from your thermo switch should be fine. The key on power wire to the relay should also be fine. Takes almost nothing to trip the relay.
overkill the size of the relay. AND GOD HELP YOU! LOSE THE BREAKER!

 

Yup. Ditch that circuit breaker, and start from scratch, as described above.

I have separate circuits for each fan, each with a 50 Amp relay, and a 30 Amp fuse.

 

Ah and what does virtually evey auto manufacturer use for engine cooling for the last couple decades?... electric fans

Someone who owned this car thought there was room for improvement with the upgrade. Perhaps they wanted that extra 7-14hp on average the clutch fans were sucking up? or they broke the factory shroud and didnt want to fight with getting a new one in the car. (good luck getting that A arm spacer/crossbar support on the car with the factory fan setup.)

Ive been running the $120 version of the fans interpon pictured above and my cooling system never worked so well even though I replaced all the original components one by one but the fan blades themselves on my 74 first I still didnt like the fact that with my 180 degree state the car would climb to 200 degrees or more sitting in traffic
I do run a dual fan derale controller and seperate breakers (yes breakers. The kind with the red arm that swings open when popped) for each fan with no issues in 3 years.

Remember electric fan only kick on when needed and they kick on and off instantly either drawing from the alternator or not. since they dont typically turn on at all when the car is moving at a decent speed they dont put any drag on the motor so NO hp loss when you want the hp most.
Mechanical direct drive fans always apply power robbing drag and clutch fans apply more drag as they close to engauge the fan when the temp gets closer to engaging them they also stay engauged for a while as the temp of the clutch slowly cools enough to let go. This is why these systems are not really ideal for performance. The 7-14hp dyno proven average is equal to what you would gain if you replaced a stock cast iron intake with a edelbrock intake and so many here feel thats a worthwhile gain/ investment so why do so many feel its taboo here? (Partially because its a lot easier to get wrong and has earned a bad rap by those that didnt install good functioning system or install it correctly)
And if you have a mechanical fan without a clutch.. God help you the losses can be closer to 40hp!

THat temp switch only has one wire because its simply a ground switch ... if you take that wire and wire it to the chassis or a good ground on the car the fans will turn on and stay on when the car is running. this is the easiest way to tell if your temp switch is the only reason the fans are off when they are. They should be applying ground to a coil on a relay or relays that are powering the fans. overkill is good here I use 2 30amp relays one for each fan and 10awg wire for each fan 12 awg minimum. Leaving the fan on all the time is NOT ideal either but you can make a bypass switch so you have an emergency on switch or do this just for testing purposes. the temp sensors are cheap so id just source another that goes with the temp rating of the thermostat you have. Id also make sure your thermostat is not part of the issue here since if it isnt opening and closing reliably or you have air in the system I believe you can get this type of behavior.

 

Does the new switch also have two connectors? This could either be a dual fan control switch or a switch with an input and output for the ground. There should be no positive 12v going to this switch. If you have it wired wrong this could be the issue
Also check you engine ground you can make a ground jumper wire to touch to the sensor housing and see if the switch kicks back on if you have a weak ground this could be the issue but its unlikely.
... You can test this with a multimeter as well and have you tried removing your themostat just to test if the flow is not consistent or there air trapped up there? You will get this behavior. I also see the wires going to both your temp gauge on top of your relay and the fan switch wires seem to be swapped in some of the pics? If that gray wire going to the temp gauge sensor was really going to your fan relay that would be one issue. since it works off resistance it might have caused the fan to turn on and off at certain temps but not correctly.

You also mention 2 relays but only picture one.

BTW powering these fans from the alternator stud is typically a bad idea. that "clump or wires" you referred to should terminate at the starter lug or battery and not the alternator. This is how its typically recommended since the closer to the battery the power comes from the better and cleaner the dc wave ive been told. the alternator outputs modified chopped AC current and the battery acts as a smoothing capacitor of sorts.

 

@4-vettes

• I admit that I have no idea how much these fans draw amperage wise. My impression was it was a lot lower than mentioned here.
• I need help in understanding the heating and subsequent opening of the circuit breaker. When this circuit breaker is tripping/popping/opening, it is doing so even when the ambient temperature is in the low 70s, out of the sun, and with the hood open. I wouldn't think this setting would cause the temperature inside the engine bay to get hot enough to trigger a response. I feel more may be going here. I have no data to back this up.
• This being said, I'm not opposed to moving on to fuses.
• What would be a suggested wire path from solenoid to left fender well?

@augiedoggy

• The new switch also has two poles. One of the wires goes to the negative side of the alternator. Attached picture shows the new temperature switch and the alternator. I have exposed the wires going to the alternator and beyond. It's a hot mess.
• I burped the cooling system a week ago. It was my first time, and I got some bubbles. With an "n of 1", I don't know if the number of bubbles I saw meant anything. For the thermostat, I get a noticeable rise in temperature of the upper radiator hose around what would/could be 180 degrees on the dashboard gauge. I take this to mean it's working.
• From any pictures I have, I wouldn't get too get caught up in the color of wires. When I mapped out the wiring for the electric fans yesterday, I had to make all sorts of notations of wire-color changes.
• I've attached a picture showing the two fan relays, the A/C relay and the infamous circuit breaker. I've also attached a picture of "the clump", which doesn't seem so clumpy in the picture.
  • The A/C relay is between the fan relays and the circuit breaker.
  • The fan relays are jumped together at position 87 and then on to the circuit breaker.
  • I don't know where the circuit breaker is getting power except from "the clump". It doesn't come from the alternator.

Bonus: the fan relays are held on by some black glue-type substance.

 

For the sake of clearing up confusion the temp sensor is a single "pole" switch with 2 wiring terminal pins.(A double pole switch connects to two separate pairs of wires and switches them both while keeping them isolated) I assume at this point its grounded to the alternator and when active it shares that ground with the relay coils to activate. if your fans truely do run consistently with this bypassed there is still something wrong with either the sensor, sensor wiring or the temps the sensor is seeing.

What is the amp value of each of the 2 circuit breakers powering the fans? (Or is everything on that one little breaker and that single 12awg wire?) Like others mentioned the breaker could be heating up, tripping and resetting itself as it cools if you had a meter or simple light bulb voltage tester you could check this.

 

At the extreme left edge of this picture, in the blue circle, I see a circuit breaker. That's likely causing your issue.

That circuit breaker is like a self resetting/self replacing "slow blow" fuse. It's a thermal device. After the current is too high for a given time, it will trip and shut off the thermal switch inside. Once the switch trips off, the thermal device starts cooling inside and eventually it will get cool enough to reset and turn the switch back on. This will repeat. How quickly it trips depends on how much current is being drawn through the breaker. It's likely that the circuit breaker isn't big enough to run both fans, or that it's just gotten weak and trips at too low of a current flow.

Those are good to run on headlights and on electric fans. But I'd usually run an independent breaker (or fuse) to each relay to power each fan from a separate breaker. If you combine them like that, one breaker takes out both fans, even if there's a wiring fault only in one fan's wiring.

It looks like you could run a mechanical fan and clutch from a truck with a serpentine belt setup. If you go that route, it will be more reliable in general and usually cools better. The fan has to be designed for counterclockwise rotation because the water pump on yours spins that direction. The stock C3 water pumps that use V belts spin clockwise, so a stock C3 fan and clutch won't work properly.

 

@augiedoggy

• Confusion on my part could only have occurred had I known two such things existed. Thanks. I assume this means I have a single pole, dual terminal switch.
• The one 30-amp circuit breaker powers (is directly connected to) both fans. I couldn't tell you the size of the wire (not enough experience yet).
• Using the meter, I assume this would be while the fans are running and then after they cut off? I ask as I was trying to determine a way of testing it without turning over the engine. I did not accomplish this goal.

@C6_Racer_X

• There is one power wire to one circuit breaker. Can I provide power to two circuit breakers or fuses from that one wire? Or do I need to run a/another line from the starter solenoid?
• I looked at my first starter solenoid today. It appears that there are two wires that are possible after-market variety which are attached to the battery terminal. They both get absorbed into the vehicle wiring harness. I was thinking of taking each of those wires off, one by one, to see if that affected the fans. Since I didn't find a reliable way of testing the wires at the circuit breaker, I held off on this approach.

@scottjamison

• It turns out that I might have either a power probe or a cheaper version of one. The instructions for use may have incorporated a less-than-ideal English translation. I may not have used it properly as I noted above. Then again, I may have needed the engine turning over for some good information.

 

OK, your a novice, we got that.
we have suggested that you start over with your wiring. One 30 amp breaker is DEFIANTLY not enough for twin fans.
So,
Do yourself a favour. Go to Mad electrical's web site. they are experts in wiring upgrades for our vintage cars. Go to there tech pages. They explain how everything should work. In a manor that a novice can understand.

 

• So, the one 30-amp circuit breaker is opening and causing the fans to stop.
• I mentioned that the wiring wasn't what I had expected. I've ordered a new dual fan wiring harness. I'll see if I can follow the directions there.
• I mentioned above that I found two additional wires on the starter solenoid. I was able to isolate the one providing power to the circuit breaker for the fans. Unfortunately, it also powers some stuff inside the cabin. I'd like to figure out what the other wire powers.

 

Do you have a wiring diagram? You can find one here:

http://wordpress.keystonestatecorvet...m/?page_id=118

In 1978, the starter extension harness provides power to the rest of the car. There are two red wires, protected by two fusible links, and two versions of this part.

With AC
https://www.zip-corvette.com/77l-78-...n-harness.html
Without AC
https://www.zip-corvette.com/77l-78-...n-harness.html

Sounds like someone spliced one of the wires to pull power for the underrated circuit breaker.