Glenn Posted August 13, 2018 Share Posted August 13, 2018 Not posted for a while as my TR7 (1977 4 speed) had been laid up for a few years. Looks all new here! Anyway, just recommissioned the car and on the first proper outing the viscous fan packed up, making a terrible noise. I'm not fussed about originality, and was thinking I would go with an electric fan and thermoswitch. I'd prefer to cut the top hose and fit a Revotec type switch unit rather than the Kenlow probe which I've found in the past can drip. My question is, if I go for a fixed temperature switch, what cut in/ cut off temperature should I look for? Anything else I need to be mindful of? thanks, Glenn Quote Link to comment Share on other sites More sharing options...
glang Posted August 13, 2018 Share Posted August 13, 2018 There is another option for controllers which Kenlowe produced before they disappeared which is a surface thermocouple. I use one and its inserts into the radiator fins under the top tank to measure the metal temperature which is then fed to a small adjustable controller to turn on the fan when needed. Its very effective, doesnt require entry into the coolant circuit and allows the cut in to be set exactly when needed.... Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted August 13, 2018 Share Posted August 13, 2018 I have an electric fan on the Dolomite 1850, the sensor is in the top hose and it's a revotec kit. It seems to work ok. (But I've had the car for less than a year... so no long term conclusions yet) The controller on mine is adjustable, I think it comes in at about 90 deg at the moment. (quite low as the settings are 70 to 120) Quote Link to comment Share on other sites More sharing options...
Beans Posted August 13, 2018 Share Posted August 13, 2018 Personally I am no fan of aftermarket electric fans. I have been using the original set up for almost 30 years now and never had any problems with them (one viscous coupling failed some 13 years ago). Reading remains rock steady on the gauge on both my current cars. But if you want to go that way bear in mind that the thermostat opens at 88°C. So that is the moment the radiator starts to work. Which means the temperature controller should be set somewhere above that. How much? I don't know! Quote Link to comment Share on other sites More sharing options...
nang Posted August 13, 2018 Share Posted August 13, 2018 New viscous couplings are available from Rimmers . I replaced my noisy one last year and all is well. Tony. Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 15, 2018 Author Share Posted August 15, 2018 Thanks all. I've removed hub and coupling now to have a better look, and both are in poor shape. Purely for cost reasons I'm going to go for an electric fan. The surface sensor sounds great but I wasn't able to see any online unfortunately. I've gone for a revotec style with switch which cuts in at 100 degrees and off at 90. The switches are pretty cheap if I need to vary that. I reckon that should hopefully keep it out of danger but keep above 88 so the thermostat doesn't close. Thanks again. Quote Link to comment Share on other sites More sharing options...
glang Posted August 15, 2018 Share Posted August 15, 2018 Ok Glenn you now got some other decisions to make: Which fan (not sure if theres a choice of in front/behind of the rad on a TR7), run on or stop with ignition off, manual overide switch or not. The airflow of the fan is directly related to the current it draws (not all manufacturers are honest about these figures) and how much you need depends on the efficiency of your cooling system. If yours tends to overheat rapidly then you probably need a more powerful fan (you cant get one thats too powerful) and obviously it sensible to fit the largest diameter possible. In the end if your cooling was ok with the mechanical fan I think an electric drawing around 10-12amps (220-240w) will do the job as well...... Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 15, 2018 Author Share Posted August 15, 2018 Thanks Glang. I can see some trial and error will be needed, and a close eye kept on the temperature gauge. It's not had any cooling problems since I've had the car. There's plenty room either side of the radiator. Are there any specific advantages of the fan being a puller or pusher? Is it an advantage to allow it to run on after the engine is off? Just wondering if that does much good when the water pump isn't pumping? Quote Link to comment Share on other sites More sharing options...
glang Posted August 15, 2018 Share Posted August 15, 2018 Blowers are generally a little bit more efficient than suckers and do leave more room around the engine however depending on the space available they may be a bit more fiddly to install. Like many modern cars mine runs with the ignition off and works very well to control excessive temperatures especially when stopping after working the engine hard. All time the thermostat is open the coolant flows by natural circulation as the fan cools it in the rad so it drops and pulls in more hot liquid. I feel this is good to reduce oil and rubber seal degredation but means I sometimes have to use choke on restarts where I wouldnt have previously plus theres always a risk of an electrical problem that causes the fan to run continuously..... Quote Link to comment Share on other sites More sharing options...
Howard Posted August 15, 2018 Share Posted August 15, 2018 I fitted a Kenlow after my original viscous coupling died and have been very pleased with it ever since. Fan only comes on when I am sitting in heavy traffic or racing up one of the alpine passes on a hot day, and bring the temperature down quickly and efficiently. Quote Link to comment Share on other sites More sharing options...
glang Posted August 16, 2018 Share Posted August 16, 2018 Yes Kenlowe are good although pretty expensive and now no longer sold for after market use. On an efficient cooling system a chinese cheapy might do the job - theyre low power (I wouldnt trust the advertised ratings) and dont expect them to have the run life of recognised makes (how much will it have to operate anyway?) but when fixed directly to the rad should cool as much as the mechanical unit on tick over..... Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 19, 2018 Author Share Posted August 19, 2018 Thanks again folks this has been very helpful. I'm going to try one of those cheapy fans. I'll power the relay coil through the ignition circuit, but if I find it often needs to run after the engine is stopped, I was planning changing to a 5 pin relay and timer relay set so fan can run on for 30 seconds or so. I'm a bit worried about more than that as the battery is quite small. Car is getting a mildly updated alternator however as have one lying about, and the old one's bearings sounded rough. I'll let you know how it works or otherwise. Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 28, 2018 Author Share Posted August 28, 2018 Got the fan installed - parts sourced from eBay for a bit under £50. I was able to try it out at the weekend and it seems to work well enough. Fan only kicks in if the car has been sitting idling for a good while, and it gets temperature down fairly quickly. Plenty of room under the nose panel, but I took the radiator out to fit the fan as I was a bit worried about damaging it with the cable ties. I wired the relay coil through the ignition, and took a fused feed off the battery to power it. If I was doing it again I'd probably just make the relay coil feed permanently live so it could run on after the engine is off. Quote Link to comment Share on other sites More sharing options...
glang Posted August 28, 2018 Share Posted August 28, 2018 Sounds good. You can always sit in the car with the ignition on for a while after stopping to see what the temperature gauge does to decide if you want to set the fan to run on at a later stage..... Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 28, 2018 Author Share Posted August 28, 2018 That's what I was thinking. I did have a think about a 3 relay timer system to allow fan to run on for a fixed period, but gave up and saw sense as far too complicated!! Quote Link to comment Share on other sites More sharing options...
glang Posted August 29, 2018 Share Posted August 29, 2018 Ive used a 75º temperature switch mounted on the radiator to energise the control system when the engine heats up. The control current draw is pretty low so the battery would probably last anyway but I like having a back up in case the fan doesnt stop for some reason.... Quote Link to comment Share on other sites More sharing options...
RobPearce Posted August 29, 2018 Share Posted August 29, 2018 Quoted from Glenn- That's what I was thinking. I did have a think about a 3 relay timer system to allow fan to run on for a fixed period, but gave up and saw sense as far too complicated!! Yes, well, being an electronics / software engineer, my solution involves a PIC micro, big FET, and some code. No relays, though, and I get to be able to run the fan at low speed with soft start, any sort of timer I want for run on, different temperature thresholds when running or stopped, and other such "far too complicated" stuff. Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 29, 2018 Author Share Posted August 29, 2018 Rob you are a bad influence. I can't resist a bit of far too complicated so feel free to give details about how it's done here please!! Quote Link to comment Share on other sites More sharing options...
Beans Posted August 29, 2018 Share Posted August 29, 2018 The fan shouldn't get the "temperature down fairly quickly" The operational temperature of the engine should remain constant ... Quote Link to comment Share on other sites More sharing options...
glang Posted August 29, 2018 Share Posted August 29, 2018 Fraid theres always got to be some deadband and in our old crude systems its larger than more modern stuff....... Quote Link to comment Share on other sites More sharing options...
RobPearce Posted August 29, 2018 Share Posted August 29, 2018 Quoted from Glenn- Rob you are a bad influence. I can't resist a bit of far too complicated so feel free to give details about how it's done here please!! Well, this is the circuit I designed. It uses surface mount components and needs appropriate code, which I wrote. I ordered the PCBs from China and I think I have a couple of spares if you want one 😆 Quote Link to comment Share on other sites More sharing options...
Glenn Posted August 30, 2018 Author Share Posted August 30, 2018 Impressive circuit Rob! I'll maybe take you up on that after I get all the other gremlins fixed. I'm not sure my system could hold a truly consistent temperature as the thermoswitch has a 10 degree range (100 on, 90 off). The temp gauge sits steady at about 1/3 on the move (as always), rising slowly to about half when sitting idling for a good few minutes. That's less deviation than my 80s watercooled VW van with factory electric fan. If I can pick up a 95-90 switch I reckon that will be about bang on, meanwhile I reckon it's not bad. I doubt the fan will be on much as it will rarely be driven in traffic or sit at idle for long. Thanks again all. Quote Link to comment Share on other sites More sharing options...
Beans Posted August 30, 2018 Share Posted August 30, 2018 Quoted from glang- Fraid theres always got to be some deadband and in our old crude systems its larger than more modern stuff....... My fairly modern Land Rover (2008) still uses a viscous coupling. And as on my TR7's the temperature remains rock steady under all conditions. So you may call it crude but it's a pretty effective system 😛 Quote Link to comment Share on other sites More sharing options...
glang Posted August 30, 2018 Share Posted August 30, 2018 Great Im pleased your systems work so well. Out of interest what does your temperature gauge do after you turn off the engine after a high speed run and watch it for, say, 10mins? Quote Link to comment Share on other sites More sharing options...
Beans Posted August 31, 2018 Share Posted August 31, 2018 I always cool down the engine (and brakes) with some gentle driving after trashing it so no problems there 😛 Quote Link to comment Share on other sites More sharing options...
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