had17462 Posted December 10, 2022 Report Share Posted December 10, 2022 Hi all, My brother has fitted an electric fan on his Tr6 with a override switch and no sensor in the radiator, he fitted it so it sucks but when using it the amp meter shows it’s discharging and the battery goes flat ,any help would be most appreciated. regards Nick Quote Link to post Share on other sites
RobH Posted December 10, 2022 Report Share Posted December 10, 2022 (edited) It is correct that a discharge should show on the ammeter If the fan is operated with the engine off, but if that happens with the engine running it probably means the alternator isn't working properly. Can you provide a wiring diagram showing how he has connected it - or failing that a fuller description ? How long is the fan running for to flatten the battery ? It really shouldn't be necessary to run it for any length of time except in slow traffic on a hot day. Edited December 10, 2022 by RobH Quote Link to post Share on other sites
astontr6 Posted December 11, 2022 Report Share Posted December 11, 2022 11 hours ago, RobH said: It is correct that a discharge should show on the ammeter If the fan is operated with the engine off, but if that happens with the engine running it probably means the alternator isn't working properly. Can you provide a wiring diagram showing how he has connected it - or failing that a fuller description ? How long is the fan running for to flatten the battery ? It really shouldn't be necessary to run it for any length of time except in slow traffic on a hot day. Its probably a case of having to use an 18 ACR alternator. I cannot see a 15 ACR is up to the job? Bruce. Quote Link to post Share on other sites
RobH Posted December 11, 2022 Report Share Posted December 11, 2022 Agreed a 15ACR will struggle a bit Bruce but the fan just shouldn't be on for long enough to flatten the battery. Quote Link to post Share on other sites
had17462 Posted December 11, 2022 Author Report Share Posted December 11, 2022 Ok guys that makes sense I will find out some more information on the alternator. regards Nick. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted December 11, 2022 Report Share Posted December 11, 2022 12 hours ago, had17462 said: Hi all, My brother has fitted an electric fan on his Tr6 with a override switch and no sensor in the radiator, he fitted it so it sucks but when using it the amp meter shows it’s discharging and the battery goes flat ,any help would be most appreciated. regards Nick How is he using the electric cooling fan? Is he switching it on only when the temperature goes up to 3/4 hot, until the temp drops to normal running temp, then turning it off or is it on continually? Quote Link to post Share on other sites
Charlie D Posted December 11, 2022 Report Share Posted December 11, 2022 12 hours ago, had17462 said: ...no sensor in the radiator... No matter what the cause of the battery flatening is, it makes sense to fit a sensor. Cheap and fairly easy to fit and makes life so much easier. Charlie Quote Link to post Share on other sites
had17462 Posted December 11, 2022 Author Report Share Posted December 11, 2022 Hi again, ok I’ve now seen it for myself ,he’s got a switch and uses it when in traffic then turns it off, it has wiring for a sensor from his old radiator but this radiator has not got the hole for one or the steel pipe below the water pump. 12.4 volts at the battery goes up to 14.3 when started when the fan is on goes down to around 13.9 but the amp meter shows plus when it’s on so I don’t know what’s going on there ,also his battery looks small 425 starting power 46 Ah. regards Nick Quote Link to post Share on other sites
RobH Posted December 11, 2022 Report Share Posted December 11, 2022 (edited) The fan is wired to the wrong side of the ammeter which is why it shows plus (charge) when the fan is on. It is easy just to connect to the battery which is why people do it, but it will give the wrong reading. 14.3 volts when the engine is running means the alternator is generating but it ought to get to around 14.7 at 3000rpm, to properly charge the battery. If it doesn't manage that, the battery will not fully charge. The fact the voltage drops to 13.9 when the fan is on means the alternator cannot provide enough current for it. Do you know what model of alternator it is ? A 15 ACR can only provide 28amps maximum but it could be that his is just not working properly anyway. I'm a little suspicious of the battery voltage at 12.4v . Off load it ought to be about 12.8 volts if it is fully charged, so again that could point to a faulty alternator never fully charging it. Edited December 11, 2022 by RobH Quote Link to post Share on other sites
Mike C Posted December 11, 2022 Report Share Posted December 11, 2022 1 hour ago, had17462 said: Hi again, ok I’ve now seen it for myself ,he’s got a switch and uses it when in traffic then turns it off, it has wiring for a sensor from his old radiator but this radiator has not got the hole for one or the steel pipe below the water pump. 12.4 volts at the battery goes up to 14.3 when started when the fan is on goes down to around 13.9 but the amp meter shows plus when it’s on so I don’t know what’s going on there ,also his battery looks small 425 starting power 46 Ah. regards Nick Your mate's using the fan when the engine's largely idling in traffic when the alternator output is very low, do this long enough with a marginal battery and it will flatten it. A long time ago, I installed a thermo fan in a Datsun 260Z with the control sensor wires entering alongside the radiator hose. The hose was then clamped over the wires. This didn't require any new holes in metallic components and worked well for 5 or 6 years, until I sold the car. Quote Link to post Share on other sites
Charlie D Posted December 12, 2022 Report Share Posted December 12, 2022 10 hours ago, Mike C said: ...the control sensor wires entering alongside the radiator hose. The hose was then clamped over the wires... This would work: https://www.ebay.co.uk/itm/151054632193 Although I have to admit I have always found this way of doing it a bit crude, but in the 1970's I think this type of thermostat was used a lot. Charlie Quote Link to post Share on other sites
Charlie D Posted December 12, 2022 Report Share Posted December 12, 2022 Here is a more up to date (and even easier) way of doing it.: https://cpc.farnell.com/kemo-electronic/m169a/module-thermostat-12vdc/dp/HK01176 You would need to operate the fan via a relay (another £5-10). The sensor is the little disc at the top of the box, which would be fixed to where ever is best to measure the temperature (Jubilee clip cushioned with rubber so as not to crush the sensor). Data sheet says you can have up to 1 mtr. of cable to connect it to the box. If you search for “Kemo M169A” you may well find it cheaper. Charlie Quote Link to post Share on other sites
had17462 Posted December 12, 2022 Author Report Share Posted December 12, 2022 Thanks all for all your help ,bigger battery and sensor seems the way to go ,I did notice there was a relay in the loom for the fan . Nick Quote Link to post Share on other sites
RobH Posted December 12, 2022 Report Share Posted December 12, 2022 Fitting a bigger battery is no good if the alternator isn't charging it properly. I should check that first. Quote Link to post Share on other sites
had17462 Posted December 12, 2022 Author Report Share Posted December 12, 2022 Ok guys the alternator is a Remy DRA0790. Nick. Quote Link to post Share on other sites
Bill944T Posted December 12, 2022 Report Share Posted December 12, 2022 Well it is rated at 45 A and probably at the limit of what the original loom and ammeter will cope with....... Regards Bill Quote Link to post Share on other sites
RobH Posted December 12, 2022 Report Share Posted December 12, 2022 Yes and 45Amps should have no trouble powering the fan and keeping the battery fully charged. I am still suspicious of that 13.9 volts you quoted when the fan is on. Did you try measuring it at 3000 rpm? It should rise towards 14.7 volts and if it doesn't there is either a bad connection somewhere, or the alternator is faulty, or the fan belt is slipping. Quote Link to post Share on other sites
had17462 Posted December 13, 2022 Author Report Share Posted December 13, 2022 Thx guys will check this out . Nick Quote Link to post Share on other sites
Grahambea Posted January 1, 2023 Report Share Posted January 1, 2023 I fitted one like this to my Land Rover when I fitted an electric fan, a bit more tidy than poking a sensor under the hose! https://www.ebay.co.uk/itm/174003529483?hash=item28836b270b:g:qn0AAOSw1jpb8~VD they do different sizes and a relay is recommended, other similar devices are available but this one worked very well for me! Graham Quote Link to post Share on other sites
Tim D. Posted January 1, 2023 Report Share Posted January 1, 2023 On 12/12/2022 at 10:17 AM, Charlie D said: This would work: https://www.ebay.co.uk/itm/151054632193 Although I have to admit I have always found this way of doing it a bit crude, but in the 1970's I think this type of thermostat was used a lot. Charlie Ive used these on a number of cars and they work well. Quote Link to post Share on other sites
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