Hey Doug,
I really appreciate the help - electrical issues are not my strong suit.
I don't like the relay that's currently on the fan I have - it's probe based & I'd prefer a screw in variety past
the thermostat. Our thermostat is 180 degrees - what temp would you set the fan to come on? Off? I'd love a link to
a heavy duty Fan Relay set up - the Be Cool version looks pricey at $122.

I'll check the wire sizes going to/from the fan. The Battery is tucked in behind the seat in the cab so there are
some long runs. How do you test/calculate for losses? I'll take another look at Spal.

Ben in Austin
1950 F1

 

Hi Ben,
Glad to help you. Why don't I suggest you PM me your phone # and I'll give you a ring. We can talk through it.

A few more thoughts for the thread:
The on / off temp would be + 10F to + 10F from your thermostat opening temp. The off temp MUST be higher than your thermostat opening temp or the fan will run non-stop.
The specs can be found of all of those switches through some online searching.

This is the relay I'd suggest along with one of those thread-in switches to trigger.

I like this relay as you can easily attach large feed and load wires. The cube / Bosch style relays that come with the pre-wired harnesses use small gauge wires, which defeats the purpose at least for a high current device like the cooling fan.

Does your AC system have a pressure switch with three or four connections on it? The second set of connections also triggers the fan relay (These switches are called trinary switch)? I also use a trinary switch to trigger the cooling fan if the AC system pressure increases (which it does quickly with no air flow through the condenser if the fan is turned off).

The second part of the switch is if the system pressure gets too high, it interrupts the power to the compressor clutch so it will disengage. This isn't the end of the world if you don't have a trinary, but it does reduce effectiveness of the system. Some pressure switches only have 2 connections. It is worth a look at yours.

Also, if your fan relays wires are coming from the battery in the rear, I'd suggest streamlining and running off of your alternator 12V+ post (but still with an inline fuse).

Doug

 

Ray makes and excellent point, all the shrouding around the radiator is very important. When I first put my big Caddy engine in, it would get a bit hot in stop and go traffic. After I added the shrouds it runs nice and cool.


Originally these old trucks had a piece of sheet metal between the lower grill valance and the bottom of the radiator, they also had the piece in the hood that nestled down on top of the radiator and a couple of little pieces on either side of the radiator.
I had fabbed a custom radiator mount for my mid 70's Dodge truck radiator that is a lot lower than the factory rad. I fabbed a piece of sheet metal that would fit between the hood latch plate and the upper tank of the radiator. My lower piece was missing so I fabbed another one. With that and the upper piece, all of the air coming through the grill is directed through the radiator. It made a big difference


Bobby

 

Thanks Bobby & Ray,
So the theory is that you need to block off the sides & above & below the radiator to "force" the air to go through the radiator?

Here are 2 schematics that Ax posted in the dark past - I was afraid this would come back to haunt me on this cooling issue. I'll check to see what I have installed - I'm guessing not much as this truck had a mid 70's shade tree mechanic "upgrade" done to it by P.O.

"Parts # 13068, 13069 side baffles, #8208 lower valance to radiator baffle, #8348 lower baffle seal (I don't know if these are the proper names for these parts but describes their function. #16613 should fit snugly to radiator tank when hood is closed"

Does everyone really still have all these baffles on their trucks?
Does mid-fifties carry these you think?

Ben in Austin
1950 F1

 

Hey Bobby,
Do you happen to have any any pics of your fabbed radiator airflow pieces? I went out & looked
- I've got pieces behind the headlights - so no air coming through there. I've got nothing below the radiator or
on the sides or up above blocking the holes where the hood latch is placed. Who knew? My whole radiator set up is
after market so I'm guessing the original pieces may not help much.

Ben in Austin
1950 F1

 

Ben. This is all great information you are getting! Ray and Bobby are right on when they are talking about trying to take advantage of the original under the hood front valance baffle and air ducting set ups or as Bobby did fabbing his own. As Doug has correctly diagnosed you have a low speed cooling issue. I had the same issue on my 56. I saw all the original baffles Ford had around the radiator under the hood. Took out the radiator the previous owner had in from a 68 Mustang then installed an O.E. type replacement from Mid-Fifty with a cheap and even small 14 inch electric fan that was on the old radiator, and man what a difference it made in stop and go and low speed cruise ! Also Doug is right on about the fan wiring. I would just add not to ground the fan to the radiator itself. I see that being done at a lot of car shows. If you ground it to the radiator you could end up with electrolysis in the cooling system which could help destroy your radiator. As Doug points out ground it somewhere close. I would find a good spot somewhere on the chassis or the frame. On mine I just ran my fan ground back to the main chassis/frame ground.

 

I agree all the baffling helps force air across the radiator core at speed, but I do not think they will do anything when sitting in traffic. Maybe I am wrong but I do not even have shrouds on my electric fans other than the fan body and they work great.
If the current radiator is big enough it simply sounds like not enough water flow or not enough air flow across the radiator when sitting still.
I dont trust aftermarket fans much, I use Haydens which are used by the OEMs or I use OEM fans from parts cars. I trust the OEMs to use parts that are rated for continuous use.
I have a used hayden fan in my 37 buick with a champion aluminum radiator, fan is controlled by an adjustable derale controller with the capillary style sender. I have the sender stuck in the radiator fins at the top corner of the radiator and tie wrapped so it cannot loosen up. Having the adjustable controller is a must have IMO. I would also prefer a screw in sender, and I bought one in case I had problems, but so far no issues. The controller is set to turn on the fan at 190 degrees and I can watch the engine temp drop immediately when the fan comes on. I am not in 100 degree weather but 90s no problem in the summer.
Does your engine temp drop when your fan kicks on in traffic or does it continue to climb?

 

Although at least one forum member will argue against my methods, the easiest, most accurate way to determine what is going on in any circuit is to measure voltage where you want it. Forget about figuring losses, you either have the voltage you need or you don't. In your case, measure voltage at the connector to the fan when everything is running and giving problems. This is assuming you have a fan plug within a foot of the fan. You want to see somewhere around 13-14 volts at the fan. For reference, it is a good idea to know what battery voltage is at this time. Remember, your engine is running slow, the Ac compressor is on, the AC blower is on, the engine cooling fan is on, and if you're stopped or in extremely heavy traffic, your brake lights are on, all competing for power.
So far as thermostatic controlled fan switches, it is so easy to run a separate over ride circuit to the relay, controlled by a simple switch in the cab. That way you know it is on.
BTW, I have a switch in the cab that controls my relay to the cooling fan on my '49F4. If I am moving at all, I do not need the fan.
Edit: Make certain the alternator belt can not slip and that you have a good strong battery.

 

Ben, I switched to a US Radiator/Cool craft copper radiator last year. Very happy with it. I bought the high efficient three row core that fits like a stock rad. All the stock air deflectors fit just fine, and you need those. My fan is a 16" spal on a home made shroud. I made the shroud about 3" deep for good flow. You don't want to choke the hot air trying to get out. I gets hot here in Colorado, too. My fan starts at 200 degrees and will keep it there in stop and go. On the highway, I've never seen 200 on a 180 thermostat.

 

Thanks Guys,
I'm taking notes. I'll pull the radiator & see if I can get some of the gaps
plugged with some sheet metal. Now you guys have me thinking I may be ok with the fan I have - I'll see if there is any improvement with the Timing/Carb. adjusted. I'm going to change the controller - the current one is $20 Advanced Auto cheapo.

If it would stay like today all year I'd be set - 74 degrees today - weird year so far. I think we've seen 60 days of rain this Spring - very odd for Texas.

Ben in Austin
1950 F1

 

Ben,
Here is a shot of my fabbed radiator mount without the front clip on, a look down at the fabbed lower valance, and the upper valance;

 

Exactly. If your problem is mostly at idle then it is something else, and with all the information already given in this thread your job will be to pinpoint the exact problem that you do have. Good luck with that Ben, lots of pretty brilliant advise here. I am learning just reading this.
On all the cars that I have done over the years I have always tried to funnel the air (while driving) through the radiator as much as possible. Plus have a fan of course, with a shroud. I have always liked the pulling fans on the motor side better than the push fans on the grill side.
One of these days we will get to Austin again and I will look you up! The north west side of Austin, would that be somewhere near 290? BTW I just saw a chart of the fastest growing cities in the country and guess which city was number one! I am sure you can tell by the traffic

 

ALL ELSE BEING EQUAL, there are only two ways to INCREASE your cooling:

1 - More coolant flow
2 - Bigger radiator

#1 will only work to the limit of the radiator and #2 is constrained by the physical dimensions we have to work with. #1 is limited by pump design, although many stock pumps' impellers can be modified - often a simple disc riveted onto the back of the stamped steel impeller will increase flow significantly.

If those two are as optimized as you can get, then you can only work to increase the EFFICIENCY of what you're using. In this regard, the best thing you can do is work AIRFLOW. At speed, the shrouds are critical. At idle, the fan is critical. In between, it's a combination until speed reaches the equivalent of the fan flow.

All of this assumes an engine in good tune, running properly. That means no head gasket leaks, optimized timing, proper air/fuel ratio, and an exhaust without too much restriction.

As a gross rule of thumb, if you're OK around town and idle, but get hot on the road, you have a radiator issue. If you're OK on the road, but struggle around town, it's more likely an airflow issue. Again, these are gross generalizations, but should get you going in the right direction.

Coolant also plays a role here. Water will transfer heat better than glycol, while glycol will increase the boiling point and resist freezing far better than water. The much-hyped 50/50 mix is a great starting point for folks who routinely experience freezing weather. However, for those of us in the south who seldom see temps below freezing for any significant duration, a 25/75 is a better starting point if you don't want to mix your own 'cocktail'. The glycol coolant also has some nice properties like anti-corrosion and water pump lubrication that water alone doesn't have. A bottle of wetting agent (water wetter, hyper cool, purple ice, etc - pick your favorite) also helps.

Lastly, do not rule out the importance of a good thermostat. I had a nicely running setup that suddenly started running just a tiny bit hot as I came off the interstate dumping the high-speed heat into the cooling system w/o the airflow for a short time, watch temps climb at the first light, then as soon as moving at all, came right back down. I had a brand new radiator and OEM-style fan, so was a little baffled. I chased a few tuning issues and did some other minor trouble shooting, but since it wasn't actually overheating, just behaving differently, I mostly ignored it. Then one day, it overheated on the highway. I got it cooled off, refilled and it was fine afterwards, but the temp was fluctuating....thermostat was sticking sometimes, but not always. :/

Often, our toys sit for weeks or even months - that's not great if you don't have a nice clean system and the thermostat can fall victim to corrosion and dirt. The rest of our system can get a film on it which will act as a thermal barrier reducing the efficiency. So a good clean and flush every once in a while is a good idea...certainly seasonally.

Electric fans are a great way to better the airflow and you've gotten some great advice regarding the wiring too (often overlooked). Generally, two smaller fans will move more air than a single larger fan. It's simple math - considering the sizes we're working with, the area of two smaller circles is greater than one larger circle and because we have a rectangular area to work with (radiator), this may be the way forward.

OEM fans often have two speeds, with "hi" only being engaged with A/C on and/or a second temp limit. Don't be afraid to hit the junkyards - I've found that a late '90s Ford Escort 2-speed fan moves a lot of air, is very quiet compared to a similarly sized aftermarket fan, and is two-speed. Is it enough for your application? Not sure, but the point is check out the OEM stuff...often cheaper, even new at the corner parts store, than aftermarket as well.

Good luck and let us know what you find.

 

The way I see it the baffling should be helpful at idle as well. With the truck just sitting there in traffic or at low RPM the fan will be drawing air, with all the baffling in place the only source for the air is through the radiator core.


Bobby

 

Thanks Guys,
I'm currently working the Timing & Carb. today to make sure that's
all set right. We have a high performance water pump in there so I think that's ok. I changed out the thermostat last month & tested it so I know we are good there.

I've studied the OEM fan setups - the Mark VIII, Ford Taurus, & even the Ford Contour all push more air than the Derale 2 speed fan I've got. Honestly I'd swap to one of these in a heartbeat If I could get them to fit.
Mark VIII needs 6.5 inches & I've only got 4 inches to work with. Both the Taurus & the Contour are dual fan setups that are 4 or 5 inches too wide. I could get some more fan room by moving the radiator forward about an inch & I could also go to a shorty waterpump & pick up another inch or so - but that would involve a lot of effort to match up the pulleys/brackets/A/C, etc. Doable but ....

Step #2 - I think my next step after the timing/carb. will be to get a better Fan Relay - the current one has the 1800 cfm fan speed on at 180 degrees & the next 2400 cfm high speed coming on 30 degrees later at 210 degrees. (I would prefer the screw in probe too).

Step #3 - I also will go with a better fan that flows 3,000 CFM & try to
work it into the existing Derale shroud. Living in Texas - I've got to get this cooling issue figured out.

Step #4 - I'm fairly certain I'll have to pull the radiator to get the fan on
there right. With the radiator out I'll plug some gaps to improve air flow.

Thanks to everyone for helping me out.

Ben in Austin
1950 F1


(Topper - when coming into Austin on 290 to right on 183 - 20 minutes out 183 to my place).