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MG Midget and Sprite Technical - Hayden fan with controller # 3652 will not work

I just installed a Hayden fan# 3670 with a non adjustable controller# 3652 and the fan will not start automatically. It should come on at 185 degrees F. and off at 180 degrees F. I have checked and rechecked the wiring which I know to be correct, according to the Hayden instruction booklet. The fan will work when wired directly to the battery. The relay has been checked and is ok. The yellow wire that goes from the radiator probe back to an ignition switched location is connected to a switched connection on the fuse block. The fan power wire (black) is connected to the orange wire which goes to through a fuse to the relay. The fuse has been checked and is good. The red power wire for the relay is directly connected to the battery. Both the fan and relay ground wires are connected to appropriate ground locations. I have considerd the fact the temp. gauge may not bee reading correctly when it reads 210 degrees F. and have applied heat of 210 degrees F. directly to the sensor, which, I believe, should have turned the fan on. Any help/advice would be appreciated. Thanks, Keith
KTM Moore

Keith
Directing heat to a temp sender in the form of a flame is a no no and can damage the sender.
The easiest way to test it is to turn the dial to a temp as low as possible.
Then it should turn on when the car is at opperating temp.
Usualy the temp scale on this type of senders is not to accurate add to that the accuracy of the temp gauge and you could have your answer.
Onno K

Onno,
Thanks very much for your response. I actually used a soldering iron to heat the sensor as I thought it would simulste the heat the sensor would get from the radiator tubes. Your suggestion to turn the dial to a temp. as low as possible was good, unfortunately my controller has two fixed temps. The fan should turn on at 185 degrees F. and off at 170 degrees F. In my original question I mistakenly indicated the fan should turn off at 180 degrees F. not 170 degrees.
I am looking forward to any further suggestions.

Keith
KTM Moore

I am going nuts with this fan problem. I can get the fan to start automatically by placing the radiator probe/switch outside of the car and applying heat directly to thr probe side of the switch. However, when I replaced the radiator probe/switch into the radiator the fan will not run, even though my laser temperature gun states the temp., at the switch, is 200degrees, and it should start at 185 degrees. According to "Hayden" this fan can be used as an additional fan and does not have to be a "replacement" fan. I am still using my origlnal 6 bladed fan and have installed the electric fan as a pusher in front of the radiator, to work in addition to my original fan. I thought the original fan might be moving air in such a way as to adversly affect the probe/switch, even though, as previously stated, the probe switch has read 200 degrees. Based on this theory I covered the probe/switch with rubber hoses on each side, essentially covering it entirely except for what is in contact with the radiator. Of course,(self depricating) this did not help. One last little bit of information: The instructions for the probe/switch state the switch must be in contact with the fins of the radiator and the probe must contact the tubes. It actually slides between two tubes and fits snugly with one tube on top of the sensor and one below it. This is how i initially installed it. Today as I was checking the probe/switch for continuity I found the probe/switch could not achieve continuity, by placing it in 200 degree water, unless the switch was actually touching the hot water. This tells me the probe does not actually transmit heat it is merely a way to attach the switch to the radiator. As the fins do not reach the 185 degree mark I removed enough of the fin material to allow the switch to touch the tubing directly. It actually only barely touches one radiator tube. Would it make sense to place a large enough washer between the tubing and switch so the washer can contact two tubes, then the switch will contact the washer which will then, in essence, have the switch contacting two tubes and hopefully achieve a better reading of the temperature?? I also fabricated a bracket and mounted it it to a thermostat housing stud which reads 200 degrees with my laser gun. Based on the fact I was able to get the fan to start remotely, as stated previously, I have attached another sensor to the bracket with the hope the heat transfer from the stud to the bracket to the sensor will start the fan. It looks funky but I was curious.
Thanks for taking the time to read this. Please do not hesitate to reply, especially if you have had a similar problem. It's 8:30pm and my wife is calling me to dinner, for the third time, so I have to go...it's a good thing I was finished anyway.

Keith
KTM Moore

I looked up the instructions for Hayden 3652, informative but appalling lacking in details! This is a snap switch, which means that the element inside the switch must be at activation temp to work. The brass rod functions as a mount and <maybe> a heat transfer conduit. These tend to be pretty constant in actuation points for any particular unit, but not so much between units. Some temp switches, like those supplied for late MGB are unbelievable awful in both set points and repeatability.

The instruction says to mount the switch behind the rad, where the switch body will heat up. Mounted in front it would not heat up enough to ever work, unless the car was very hot and stationary. Even behind the rad, wash from the engine driven fan could keep the switch below trip point. You could cover and insulate the switch against the rad, or glue it on with heat conductive epoxy. A heat transfer compound might help, but I don't know if there is anything that wouldn't melt and fall out - they are normally for tight bolted joints. The brass rod could act as a conduit to move heat from the switch toward the cold end of the rod sticking out the front into the airstream, so that should also be covered.

All this will help to get the switch temp up to the temp of the rad where the switch is mounted, BUT...
there is a temp gradient from the hot tank to the cold, say about 50-60 degrees. Where you put the switch makes a LOT of difference. We usually speak of water temps at the head, which can be taken as approximately the hot tank temp, when the stat is open. Let's say that is 200F, when the cold tank temp will be 140-150F. The stated actuating points are 185F ON, 165F OFF. You can see that on the hot side the switch will always be ON, running the fan continuously, and on the cold side it will never come on, even if the head water temp is at 230F. Worse yet, if you have a partially blocked rad which really does cause overheating, and you happen to mount the switch in the blocked area, it will never come ON.

Bottom line is that switch actuating temp has NO direct relationship to water temps - it all depends on how and where it is mounted.

The IR guns are convenient and not precise at the best of times; one point is that the laser pointer only registers at the sensing point at one range - just like sighting in a rifle, at close range the aim & sense points may be a couple of inches different - get a real thermometer to read hot tank temps. Decent but affordable Multi-meters today come with thermocouple probes which are very good, though I always check the boiling point calibrations.

Rule of thumb is that fan ON should be 15-20 deg F above Tstat open, and OFF should be no lower than Tstat open, or better at 5-10 deg above. Otherwise, you run the fan far too much, and have the stat trying to keep the water hot while the fan tries to cool it. You should be running a 180 stat minimum, and 190/195 is better for the engine year round. So long as your cooling system is good, you can safely run at 230 or more, with suitable pressure cap and 50% glycol. A 15psi cap will run over 250F without boiling.

Example of modern car: My Mazda has a 195 stat and fan ON is at 210, fan OFF about 200. I can drive for weeks even in summer without the fan coming ON, except after shutdown, when it runs for a few minutes. In winter it comes ON so rarely that it frightens me.

FRM
FR Millmore

I didn't want to put anything until you'd got a much more informed reply than I was ever able to give

this fan unit you have sounded like hard work to me, plus you've already bought it, and I don't know if you get the Revotec fan units and thermo switches over there (I expect you get Kenlowe)

personally I think you should be able to fully commit to a good thermo switch electric fan without either over-ride switch or engine driven fan

subject of course to all of your cooling and heating system and coolant/antifreeze being in good condition but you’d need that with any fan system

you accept an electric fan system only in other vehicles without any thought about it, sure if the electric fan stops you could overheat but how often does that happen?

if you don’t regularly change it it’s more likely to happen if your fan belt slips or breaks

electric fans are more efficient in as much they only work when needed rather than all the time and unlike the engine driven fan they’re not counter productive by working when not needed at greater speeds with more cooling air and operating when not required keeping the engine cooler in the cold and slowing down the engine from warming up

be happy with your weather as over here most of the time my engine overcools :)
Nigel Atkins

Nigel and FRM,

Thanks very much for taking the time to help me. I am a new member and am greatly impressed with the knowledge of the members and their passion to help others. I just installed a new twist on oil filter assembly, my son bought for my birthday, and will take the car out on Friday the 27th. as the temp. should be in the mid 80's. I will see if the fan turns on under driving conditions verses the car idling in the garage.

Keith
KTM Moore

Hi KTM,

I have Hayden fan too and with the same problem. Solved by adding manual on/off switch installed hidden under the dash. And I switch it on/off manually when needed (city traffic, hills etc.). Ideal solution - at least works for for me.

Stepan
Stepan Marek

Keith,
FRM is very knowledgeable and experienced plys he know the American cars that vary quite a bit in some areas and have a lot of additional safety bits on them

a road test is a great idea just check your cooling system are in good condition

I have my fan wire via a fuse direct to the battery so that it runs on and continues to cool after I've parked the car, this I find to be good, it does of course require a battery and charging system up to the job and in good condition but again you always want these in good condition - if your still on a dynamo then this might not be such a good idea

no matter which fan system you have you want it to have to do as little work as posssible by having your coolant and cooling systems in good condition

I've got some general notes on this if you want them

try and enjoy your drive as well as testing, you'll soon now if the electric fan is going to work by getting ther car fully warmed up and then pulling over and switching off the engine but leave the ignition on that way the engine driven fan and water pump will not be operating so the temperature will soon rise giving a chance for the ignition switch electric fan a chance to show when it's going to work if it's not already running

ETA: typing whilst Stepan posted - that would do away with the the troublesome thermoswitch

bit like having a dog and barking yourself to me but an economic solution
Nigel Atkins

Nigel,

yes, you are right with dog and barking :-)
Just to add - I have it this way - thermoswitch can "overrule" manual switch, eg. if I forget to switch it on manually, thermoswitch will do that, even though at the moment when temperature hits "H" mark on the gauge ('73 car).
I added manual switch because I was afraid it is a bit too late. And I also use the same direct to battery connection for cooling with ignition off. At the end - I really need to switch it on manually rarely, only in city traffic or long hill climbs and hot weather condition (and I don't have standard 6 blade fan in place).
S.
Stepan Marek

I've got the Revotec kit on a X-flow rad and engine fan removed

the thermoswitch is cut into the top hose with temp adjustment, this is very good as you can set when the fan cuts in over a wide range

I have mine set so that it only goes just past the N when the car is stopped and engine off, when on the move and fan off mine temp sits well before the N

the Revotec fan is fitted in front of the radiator (other side to engine) it's a narrow profile fan which obviously doesn't matter when fitted in front of the radiator so if I was doing it again I would fit a deeper fan like the kenlowe and combine it with the Revotec thermoswitch

I've had electric fans before and never bothered with overrides switches as I said electric fans have been on cars for decades and we don't worry about override switches

with that Hayden unit I can see this is a solution personally I'd give up on it just keeping the fan unit if it's any good and using a different thermoswitch

don't forget your oil system is your secondary engine cooling system so good thorough oil changes and using a good quality oil will help your primary coolant system of 'water'

the thing I've found is not to let the heat get too high in the first place rather than then trying to get rid of it

I had a model of car that was know for sitting just below the red on the temp gauge because of it's lack of full (English) design, just below the red leaves very little margin should circumstances get awkward so I just swapped the fixed temperature thermoswitch for a lower temperature one that switch the fans on sooner and the problem was solved
Nigel Atkins

This thread was discussed between 16/01/2012 and 27/01/2012

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