Electric Rad Fan Control

[West Coast GT]

Thanks for the tips regarding the alternator bracket.

This electrical upgrade project includes installing an electric radiator fan. I've got a thermoswitch that will automat the fan's operation. Instructions tell me to install it in the cylinder head or intake manifold.

Questions:

1. What other locations have you guys located the sensor?
2. Do you foresee any problem drilling & tapping a hole into the upper or lower radiator tank for this sensor?
3. Just a thought; have any of you combined the thermoswitch with the existing temperature gage sensor?

Thanks in advance,
Keith

[tomking]

Thanks for the tips regarding the alternator bracket.

This electrical upgrade project includes installing an electric radiator fan. I've got a thermoswitch that will automat the fan's operation. Instructions tell me to install it in the cylinder head or intake manifold.

Questions:

1. What other locations have you guys located the sensor?
2. Do you foresee any problem drilling & tapping a hole into the upper or lower radiator tank for this sensor?
3. Just a thought; have any of you combined the thermoswitch with the existing temperature gage sensor?

Thanks in advance,
Keith

While I have not done this modification yet, you cant drill and tap the rad tank. You will have to braze in a fitting to go that way. No problem though for a rad shop.

[namba209 (R.I.P.)]

Keith, if you put the sensor in the radiator, use the top tank. Most cars use the upper location, either in the head or manifold. There are some sensors that pick up the temp from the upper radiator hose, also. Tom is correct, a radiator shop can install one for you, either by removing the upper tank or just drilling and brazing/soldering from the outside.

[kwilford]

Moderator Note: Posts split off to their own thread, as this is "Cooling" stuff not "Starting and Charging"

I totally don't think that the radiator fan switch should be in the cylinder head or intake manifold. That temperature should be controlled by the thermostat, not the rad fan operation.

I think that most modern cars have their radiator fan sensor in the bottom tank, or at whatever position that the coolant occupies just before it is sent back to the engine. The top tank in the Opel would have the hottest coolant, as it would just have arrived from the engine. No sense running the fan to cool the fluid down based on the top tank temperature, as it may have sufficiently cooled down by the time it leaves the radiator just by the air flow caused by the car speed. That's the main reason for the sensor, to let the fan to NOT run if not required.

JM2CW

[dallasmanta]

keith,

I have this done on both my MGB and Manta and have used a variable control from Autozone. The probe bulb is designed to be on the engine side of the radiator picking up the air temp coming off the radiator.

I have found that if you do not have a screw inn plug braised in to the bottom edge of the upper tank that accepts a standard bosch on off swith from any number of european cars you will get variable temp sensingn going on by the sensor and the fans will not operate as well as you will want. This is due to no direct contact with the radiator fluid for the most accurate temp sensing.

The compromise I made was to zip tie the probe to the upper copper tank on my mgb that accomplices the same as a screw in sensor. Since I run AC on both cars I have the ability to change the on off points for the fans start and stop function to compensate for summer or winter driving with or with out ac on. The physical contact with the copper tank is more accurate then air temp coming off the radiator when in stop and go traffic. Ron

[namba209 (R.I.P.)]

I think that most modern cars have their radiator fan sensor in the bottom tank, or at whatever position that the coolant occupies just before it is sent back to the engine. The top tank in the Opel would have the hottest coolant, as it would just have arrived from the engine. No sense running the fan to cool the fluid down based on the top tank temperature, as it may have sufficiently cooled down by the time it leaves the radiator just by the air flow caused by the car speed. That's the main reason for the sensor, to let the fan to NOT run if not required.

JM2CW

Actually Keith, most newer computer controlled cars have two sensors located just before the coolant leaves the engine to the radiator. One, for the temp gauge and one for the fan switch. Your point is well taken though, the fan sensor on Willit? turns on the fan at 220 degrees, well after the thermostat has opened and coolant is flowing through the radiator and engine. I've noted that above 40 MPH the fan doesn't cycle on and off as much as in stop and go driving.

[dallasmanta]

Namba aka Ron

Very good point on the placement of coolant on newer cars with good coolant flow.

On my 75 Manta with the bypass hose and the FI setup I went for the top of the tank because the temp gauge sensor is located in the thermostat housing showing temp on the dash gauge. I wanted to keep the dash gauge in the middle at a constant temp and then adjust the variable fan switch to come on and off to keep this temp in the same zone.

I do run a 3 core radiator but with AC generating additional heat down here. i have found that if the under hood temps go up too much it is hard for the fans to keep up with heat extraction from such a small surface area. Remember the Manta radiator has about on third of the surface area below the grill and blocked for direct ram air.
My focus was to keep the engine at normal operating temp for the FI system and minimize the chance of cracking the 75 head from overheat issues since I run AC most of the time. With a 160 thermostat Normal operating temp for the cooling system runs about 180 to 200 range

I did try the sensor at the bottom tank and found that the fans could not keep up with the double demand of engine and AC cooling. I kept loosing coolant from the over flow. My only fear was the the top tank would not have enough coolant in it all the time so I added a closed system with an overflow tank that allows for expansion and contraction of the radiator fluid with out effecting the level of fluid in the upper tank. Ron

[jtb]

[*]Just a thought; have any of you combined the thermoswitch with the existing temperature gage sensor?

I saw this in a summit racing catalog, neat but pricey, it's a temperature gauge with a programmable fan control built in.
CSR Performance 1225 - CSR Digital Temperature Gauges/Controllers - summitracing.com
May not be what you are looking for, but I thought I'd stick it in the thread for others who may search through it.

jtb

[ddoyle]

Almost nothing modern uses a switch to turn a cooling fan on. That task is done by the PCM, ECM or whatever name you want to use. The sensors send the coolant temp info to the PCM the PCM uses a map based on this and many other inputs, A/C input, intake air temp, speed, trans gear, and others I am sure. Designs that did use a switch in the intake or head or water outlet will generally have a mutch higher fan turn on temp(I have recorded as high as 250F at one of these sensors before fan turn on). I would say 98% of the stuff I have seen with a dedicated fan turn on switch(older) in the radiator, honda, mitsi, lots of smaller chry stuff, volvo, bmw and others, that sensor was always in the lower tank. Some volvos and alfas on the side tank(crossflow rad) but opposite the inlet tank. I think you would need to determine what temp you would want your fan to come on, find the right switch and install in the bottom tank after the radiator has done what it can. Always eceptions of course, with A/C on, I like to see the fan on all the time.

Dan

[blancojp]

I hate to say this but the Jap cars have a small adapter that goes on the top coolant hose which handles temperature and fans. There are also small fan controllers with temp probes that can be found at any hotrod shop for about $40.

Most 12" fans have a consumption of about 8 amps. Fan switches from VW or AUDI can handle 15 amps and can be mounted anywhere on the cooling circuit and cost $20 at Autozone.

[ddoyle]

Well I have seen a few like that, think it was like late '80s very early '90s dodge and plymouth mitsu made cars. The probes work good, no cutting or rad removal needed and most of them are adjustable.

Dan

[wrench459]

hummm
The t-stat controls engine temp.
When the vehicle is moving there should be enough air flow across the rad. to cool the fluid. or is there?
Hot fluids rise cooler fluids sink. It might be a good time to look at early honda's with there fan switch in the lower rad. tank.

[ddoyle]

I will add my take on thermostats. More of a flow regulator than a temp control device. It keeps the coolant recirculating in the engine during warm up. This gets the engine up to an efficient operating temp quickly. Then the t-stat starts to open and allow flow to the rad for cooling to take place. Once the t-stat is fully open, this is normally about 15F more than the rating of the t-stat, 195F stat, fully open about 210F, it has little to do with controlling temp. It still acts as a regulator by the restriction it creates in the coolant flow. With no t-stat or regulator it is very easy to have overcooling or undercooling. If coolant moves too fast thru the rad, not enough time for heat to be removed, runs hot. Or a system with a slower flow rate, larger more efficent rad too much cooling could take place and the engine may not reach its best operating temp. Every system is different and a lot of variables come into play, its a balancing act.

Dan

[West Coast GT]

In response to a question in another thread asking for project specifics, here is a list of components from Summit Racing for my traditional fan to electric conversion:

1. SUM-890015 (185 F on, 175 F off, fan relay kit. $45.95
2. SUM-G4901 (10 inch, 6.8 amp, 2.25 deep, 755 cfm) electric fan. $52.95

The relay kit comes with a brass threaded thermoswitch, which I am installing in the lower radiator tank, near the hose outlet.

I have not decided whether or not to utilize the manual switch option. I'll wait and see how well the automatic control works.

The relay kit includes a sealed circuit breaker (which I assume is automatic re-setting or the GT will be riding the "Flatbed of Shame" home some day).

The circuit breaker and relay are mounted on the radiator cross brace just behind the brake booster. It should protect these items from road grime.

755 cfm is probably a bit light if the GT has power modifications. Mine is stock. We do occasionally get into high temps out in the Central Valley and Sierra foothills. I compromised with a smaller fan hoping it would fit without having to relocate the battery. I also bought a smaller battery incase I needed the extra room.

[newman27]

In response to a question in another thread asking for project specifics, here is a list of components from Summit Racing for my traditional fan to electric conversion:

1. SUM-890015 (185 F on, 175 F off, fan relay kit. $45.95
2. SUM-G4901 (10 inch, 6.8 amp, 2.25 deep, 755 cfm) electric fan. $52.95

...

Did you post pictures somewhere? If not, could you post a few?

Thanks,

Matt

[West Coast GT]

Did you post pictures somewhere? If not, could you post a few?

Thanks,

Matt

I have not posted photos yet, but will when I wrap the project up this afternoon. (I had to put the project on hold for a few days)

[West Coast GT]

The electric fan installation is a failure at this point.

I fired the engine up and let it run until the temperature was very hot. The electric fan failed to activate automatically. In a panic I grabbed the auxiliary manual switch lead (I elected to not install a manual switch), stripped it and held it to a live lug on the fan's circuit breaker. Fan ran for about five minutes, quit, and has not worked since.

Tonight I pulled it out and replaced the old water pump driven fan for the upcoming trip to Tacoma.

[jeff denton]

Bummer.
I hadn't been following this, just now looked at it.
First problem, a ten-inch fan may not be flowing air through the entire radiator, only a spot of it. Is there a shroud there to make sure air is flowing evenly through every tube?
I doubt you fried the fan, unless it was a POS. Maybe just tripped the breaker?
I use a Honda Accord rad and fan setup. Twin fans, even, with the whole shroud and all. It really moves air. The sensor is in the bottom tank but I don't use it. I control mine manually, if the car is racing it isn't needed but if we go yellow or red I switch it on until just before we go green again. I switch it on again before shutting the engine off. Both fans operate simultaneously to keep it simple. I want it to either move as much air as possible or none at all.
You used the term "very hot" as a parameter, but that doesn't give us much to work with. You really need a good (quality)temp gauge installed at the thermostat housing to know how hot it is.
Don't give up, this will work eventually!
Edit. Oh, wait, I see the problem. It didn't activate automatically. Move the temp sensor to the top. Test the fan with a hot wire to make sure it's motor isn't fried somehow. The sensor can be tested with an ohmeter and a pan of water on the stove with a thermometer in it. Check everything out and try again! Remember when the car is running with fan off, the bottom tank should be almost as warm as the top, and the side of the block should be the same temp. Here is where the infrared temp gun is so fun to play with. I don't know how I survived without one long ago... You just have to experiment here, as pointed out it is a balancing act. You are balancing temps, when it's right the top tank should be the hottest, the side of the block should be warm, and the bottom tank should be cold, comparitively.
Another thing I found useful: block the bypass. I don't want the hot water going anywhere but to the top of the radiator. I plug it on the water pump housing.

[West Coast GT]

Background:
I converted to electric radiator fan just before the Tacoma Gathering. The fan failed to come on automatically, so I converted back to the old belt driven fan for the 1500 mile trip.

Status:
Now I am re-converting to the electric fan and I just can't get it to function properly.

What I've tested & confirmed:
a. Received a new relay from Summit - did not fix the problem.

b. The fan motor works by jumping a hot wire directly to the positive connection on the fan. So I know the fan works, and it has a good ground.

c. All wire is good from the relay base to 1) fan connection, 2) thermo switch, 3) 12 volt supply (including the circuit breaker, 4) to the manual switch (not yet connected to a switch or 12 volt source).

d. 12 volt supply is good through the circuit breaker to Lug No. 30 on the relay.

e. Ground wire from the radiator to the car frame is good. (I added this because I couldn't come up with another idea)

What I'm not sure of:
1. The thermo switch operation; I had assumed it grounds out when it gets to a specific temperature range. But I haven't verified this yet. If this is the case I may have negated the ground by liberal use of teflon tape on the threads. Does anyone know if this is like a thermocouple and sends a positive charge back to the relay?

2. How the relay solenoid is grounded; Through the thermo switch? Or perhaps it grounds through the fan via the fan's ground wire?

3. The five basic relay connections (they seem to me to be universal)
Lug No. 30 - heavy gage positive relay supply from the circuit breaker
Lug No. 87 - heavy gage switched connection to fan motor
Lug No. 87A - not used
Lug No. 86 - connection from thermo switch
Lug No. 85 - connection from a 12 volt manual dash switch (not used at this time)

I hesitate to remove the thermoswitch because my garage is full of contaminated coolant I'm having trouble disposing of in a legal manner. I'd much prefer to resolve this fan problem without adding to my storage situation.

Any ideas? Do you see anything that jumps out and says, "Here's your problem"?

[trlmr]

I don't know if your thermo switch closes the circuit by grounding or completing a circuit. Does it have one wire to it or two? If it has one it is a grounding switch. If two it should complete a circuit. If it is a grounding switch it should go to terminal 85 with terminal 86 hooked to a power source. If it is a switch with two wires that completes a circuit one of the wires should go a power source and the other to terminal 86 with terminal 85 to ground. the way you have it wired will work if it is a grounding switch (it doesn't really matter if terminal 85 or 86 is ground) but terminal 85 that you have hooked to a dash switch has to supply 12v power. I hope I explained this well enough, Good Luck.