johny Posted November 4, 2021 Report Share Posted November 4, 2021 For the diode to prevent a generated reverse current powering the LED it would have to be installed in the positive tail of the fan and so be rated to carry the full running current. Perhaps you could install the system without it to start with and later fit one if theres a issue... No problem with using another switch with the controller and in fact Revotec themselves offer other on-off type switches with diagrams for each on their site. Link to comment Share on other sites More sharing options...
NonMember Posted November 4, 2021 Report Share Posted November 4, 2021 That mostly looks sensible but a couple of points: - the diode: why? I don't think it serves any purpose where it is. If the relay were to chatter while the fan was jammed, then it might protect the LED indicator from inductive back EMF, if it needs such protection, but it's probably not the best way to do so even if you felt that necessary. It's not going to do anything else for you. - the fuse on the LED circuit doesn't need to be 5A, or even 2-3A. If you can find a 100mA fuse, that would be a better match. I can't see any reason you can't use a different switch but I'm not sure the one you showed an eBay page for is the one you want. I'd think this one or this one would be better (although other suppliers may be easier for you). Link to comment Share on other sites More sharing options...
Black Cat Posted November 5, 2021 Author Report Share Posted November 5, 2021 Ok then, drop the diode for now at least and fit a smaller rated fuse to the LED light. I'll get started on it tomorrow then, wish me luck. Many thanks for all your help and guidance. Link to comment Share on other sites More sharing options...
Black Cat Posted November 7, 2021 Author Report Share Posted November 7, 2021 Fitted the Revotec Fan Controller but for now without the override switch and all seems to be working OK. Set the fan to come on once the temperature reaches 70 deg which it did and once the engine was switch off the fan ran on for a few more minutes, so all seems good. My one reservation is the top of the radiator was getting hot as you would expect but the bottom hose was quite cold in comparison, could there be an airlock preventing the water circulating or is there another reason as I would have thought the bottom hose would have been a bit warmer. This is the first time the engine has been run since the rebuild. The internal heater was also getting hot. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted November 7, 2021 Report Share Posted November 7, 2021 The water at the top will naturally be hotter, so the lower hose will be cool water that has run down through the radiator; expect it to be slightly cooler but it shouldn't be stone cold. I wouldn't expect an airlock in that area; provided the radiator is flushed and unblocked of any debris then the water should still find its' way down and back into the hose for circulation, and if your heater is working then the water is getting at least that far. If in any doubt remove the lower hose, drain and flush, and refit. Did you try it after a drive, or just idling? Sometimes it takes a good spirited drive to clear any bubbles from the system. Link to comment Share on other sites More sharing options...
johny Posted November 7, 2021 Report Share Posted November 7, 2021 You really need to see what the temperature gauge is doing. the fan shouldnt come on until the needle starts to move from its normal running position. You might have it set to run too much in which case the return water (bottom hose) will be too cool and the engine runs cold. Agree with Colin that an air lock is unlikely and anyway if persistant would quickly show as overheating when driving. I would go for a drive with the fan turned off and hopefully the gauge will settle around the halfway mark. Then when home run the engine until the gauge gets back to the same position and rising at which point the fan should be set to start.... It can take a few attempts to get right but remember the fan should stop when moving at anything more than about walking pace because the natural airflow will be greater than the fan can give anyway so its just a waste. Link to comment Share on other sites More sharing options...
NonMember Posted November 7, 2021 Report Share Posted November 7, 2021 As johny says, your 70 degrees sounds far too low if it's a top hose sensor. That's probably why the bottom hose stayed cold. Link to comment Share on other sites More sharing options...
PeteH Posted November 7, 2021 Report Share Posted November 7, 2021 The thermostat, shouldn't open below 78degC anyway So IMV setting the fan cut in should surely be above that?. With a 4psi Rad Cap it won`t boil below about 107degC. Pete Link to comment Share on other sites More sharing options...
Black Cat Posted November 7, 2021 Author Report Share Posted November 7, 2021 Can't yet take it for a run, not quite roadworthy and still sorn. I'd set the temp. low so the fan would cut in before it got too hot, maybe I need to adjust the setting a little so the fan cuts in a little later? The temperature control unit is fitted in the bottom of the top hose. There shouldn't be any need to flush out the rad as it’s a new wide aluminium radiator and as I said previously the engine has been completely stripped down cleaned and rebuilt so not expecting any blockages in the engine. The temperature gauge is not connected at the moment so can't check that either. Will get it connected during the week and try again. Where should the temperature needle point to roughly when the water reaches the correct temperature as on my gauge there are only a number of marks, no temperature indications and no red zone indicated? Link to comment Share on other sites More sharing options...
johny Posted November 7, 2021 Report Share Posted November 7, 2021 The gauges arent meant to be accurate for actual temperature but more for indicating change. This is why you need to find its usual running position (normally around half way) and then adjust so that the fan is running before the needle reaches one division higher and then hopefully comes back to its initial position. Unless you have used waterless coolant you cant do any damage to the engine as the radiator cap will lift and discharge a cloud of steam to let you know theres a problem☺️ Link to comment Share on other sites More sharing options...
Iain T Posted November 7, 2021 Report Share Posted November 7, 2021 22 minutes ago, Black Cat said: I'd set the temp. low so the fan would cut in before it got too hot, maybe I need to adjust the setting a little so the fan cuts in a little later? I have my electric fan temp set at just over 90 degrees. Works fine, engines need to be hot to run efficiently. I also have a manual worry switch. Iain Link to comment Share on other sites More sharing options...
chrishawley Posted November 7, 2021 Report Share Posted November 7, 2021 Assuming no faults in the system (most notably faulty voltage regulator) Smith gauges are reasonably well calibrated. The ordinary 'correct' reading is bang in the middle. Maybe a tadge lower under cold ambient temperatures but never significantly over the midway. By the time it gets to 3/4 misfiring is a distinct possibility. Your 'hot top, cold bottom' is perhaps understandable, and ok: Hot water from the head comes in through the top hose and cold (cooled) water goes via the bottom hose into the block. Given you've got a pristine full width ali rad the capacity to disperse heat is probably greatly increased over a standard setup. In fine tuning the set it's perhaps relevant to keep in mind the thermostat as having some influence and there are three common options 75, 82, and 88 degree (nominal) opening. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted November 7, 2021 Report Share Posted November 7, 2021 35 minutes ago, chrishawley said: Given you've got a pristine full width ali rad the capacity to disperse heat is probably greatly increased over a standard setup. Didn't realise it was an alloy rad. Given that, along with the electric fan, it might be overcooling. It should be easy enough to rig up a gauge, just in the engine bay, to see what temperature it actually is reaching. On mine the gauge read just slightly under half way; it rose to exactly half way, or very slightly over, if static in traffic, and that was engine fan only. Link to comment Share on other sites More sharing options...
Black Cat Posted November 10, 2021 Author Report Share Posted November 10, 2021 Adjusted the temperature setting on the fan controller today, moved it up about three notches, think it should be about 85 deg. now before the fan cuts in, started up the car and after about 10 minutes felt the bottom hose and it was getting warm and after a few more minutes the fan cut in so all seems to be working OK. Next step is to install the override switch and the warning light then tidy up the wiring. Many thanks for all the help and guidance Link to comment Share on other sites More sharing options...
NonMember Posted November 10, 2021 Report Share Posted November 10, 2021 That's good. Once you've got the gauge wired up and can see where it gets to, I suggest you'll probably want to adjust the fan controller another notch or two up, if your 85C estimate is correct. It's far too easy to get panicked about hot coolant - as Iain T says, engines actually work best when the coolant is hot, so what you want is to get it hot as quickly as possible and for the fan only to come on if it's edging above "hot" to "very hot". 1 Link to comment Share on other sites More sharing options...
PeteH Posted November 10, 2021 Report Share Posted November 10, 2021 Ive got one of those infrared thermometers. It`s a useful tool for such things, you can measure quite specific points as a guide to how the Engine is functioning. Even got used to measure flue temperature on a wood burner!, To see if the upper flue was above dew point. Pete Link to comment Share on other sites More sharing options...
DVD3500 Posted November 11, 2021 Report Share Posted November 11, 2021 I use it when deep frying food to make sure the oil is always at the right temp... 1 Link to comment Share on other sites More sharing options...
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