Ian589 Posted August 13, 2023 Report Share Posted August 13, 2023 I've got a old 1999 Bultaco Sherco 2.5 not been used in a few years but the fan doesn't seem to cut in. I've tested the fan separately and know that that works, I've also bypassed the temperature sensor but still the fan doesn't work. Apart from the fan not working everything else seems fine, although a little difficult to start (it's a Sherco so expected) it runs fine. Any help appreciated. Ian. Quote Link to comment Share on other sites More sharing options...
lemur Posted August 13, 2023 Report Share Posted August 13, 2023 Service manual shows the fan is controlled by the CDI unit and they detail how to meter test the thermostat in hot water. On my 315 Cota the fan would kick on in the middle of a section and the idle would drop enough to risk stalling, so I put a bypass toggle switch on the fan circuit and that was handy. Better to have too much air movement then not enough. I always start trouble-shooting electric problems at the source, so meter test of the alternator windings is the best place to start, also detailed in the service manual. Quote Link to comment Share on other sites More sharing options...
Ian589 Posted August 13, 2023 Author Report Share Posted August 13, 2023 Thank you for your reply. Where can I get a copy of the service manual? Is it available online? Quote Link to comment Share on other sites More sharing options...
majesty Posted August 13, 2023 Report Share Posted August 13, 2023 Does this help Ian ? https://www.sherco.com/wp-content/uploads/2001ServiceManual.pdf Quote Link to comment Share on other sites More sharing options...
turbofurball Posted August 14, 2023 Report Share Posted August 14, 2023 15 hours ago, majesty said: Does this help Ian ? https://www.sherco.com/wp-content/uploads/2001ServiceManual.pdf That doesn't have anything more than servicing information on it, it's the workshop manual that's needed (which I don't have a copy of, lol) Quote Link to comment Share on other sites More sharing options...
lemur Posted August 14, 2023 Report Share Posted August 14, 2023 Search harder -> https://www.mrsltd.co.uk/Catalogue/Sherco-Manuals-Parts-Books/Manuals/Trials Quote Link to comment Share on other sites More sharing options...
turbofurball Posted August 14, 2023 Report Share Posted August 14, 2023 Mí amigo, none of those are for a 1999 bike Quote Link to comment Share on other sites More sharing options...
lemur Posted August 14, 2023 Report Share Posted August 14, 2023 (edited) 30 minutes ago, turbofurball said: Mí amigo, none of those are for a 1999 bike How much do you figure has changed? We are talking about trouble-shooting one of the most simple electrical systems in existence. If you were ordering parts it might make a difference but a thermostat control on a fan is as basic as it gets, it's just a switch that turns on when you heat a sensor, if you don't trust the thermostat you can bypass it with a toggle switch. If bypassing the switch doesn't work then he has a problem with power generation and the test procedure for an alternator, rectifier and regulator is unchanged. Edited August 14, 2023 by lemur 1 Quote Link to comment Share on other sites More sharing options...
reggie Posted August 14, 2023 Report Share Posted August 14, 2023 Ian 589 the 1999 Sherco by Bultaco cooling fan wiring is similar to this GasGas wiring Good luck Quote Link to comment Share on other sites More sharing options...
tony27 Posted August 16, 2023 Report Share Posted August 16, 2023 On 8/13/2023 at 10:39 PM, Ian589 said: I've got a old 1999 Bultaco Sherco 2.5 not been used in a few years but the fan doesn't seem to cut in. I've tested the fan separately and know that that works, I've also bypassed the temperature sensor but still the fan doesn't work. Apart from the fan not working everything else seems fine, although a little difficult to start (it's a Sherco so expected) it runs fine. Any help appreciated. Ian. When you say you've bypassed the thermoswitch did you do that with a short piece of wire with 2 spade terminals plugged in place of it? That will tell you if there is power when the motor is running, I still carry 1 of those in my spares as insurance Your problem is possibly the rectifier for the fan which is 1 of the 2 small pieces up in the steering head Splat Shop - Sherco Radiator Fan Rectifier Quote Link to comment Share on other sites More sharing options...
turbofurball Posted August 16, 2023 Report Share Posted August 16, 2023 On 8/14/2023 at 4:40 PM, lemur said: How much do you figure has changed? We are talking about trouble-shooting one of the most simple electrical systems in existence. If you were ordering parts it might make a difference but a thermostat control on a fan is as basic as it gets, it's just a switch that turns on when you heat a sensor, if you don't trust the thermostat you can bypass it with a toggle switch. If bypassing the switch doesn't work then he has a problem with power generation and the test procedure for an alternator, rectifier and regulator is unchanged. You mentioned above that there is fan controller in the CDI unit, which may well be different for an older and far more basic bike Quote Link to comment Share on other sites More sharing options...
lemur Posted August 17, 2023 Report Share Posted August 17, 2023 On 8/16/2023 at 4:30 AM, turbofurball said: You mentioned above that there is fan controller in the CDI unit, which may well be different for an older and far more basic bike Indeed, his is even more simple, it has fewer parts by one and one less component connection to be concerned about. The fan and its power requirements are virtually the same. Quote Link to comment Share on other sites More sharing options...
Ian589 Posted September 4, 2023 Author Report Share Posted September 4, 2023 Am I right in assuming if the bike starts OK this means that the stator/alternator is not the problem? Quote Link to comment Share on other sites More sharing options...
lemur Posted September 4, 2023 Report Share Posted September 4, 2023 (edited) 4 minutes ago, Ian589 said: Am I right in assuming if the bike starts OK this means that the stator/alternator is not the problem? It's a good indication yes, unless you need additional power for lights or batteries. Very encouraging, that's where the fan comes in because there can be and are often separate coils dedicated for that. Edited September 4, 2023 by lemur Quote Link to comment Share on other sites More sharing options...
lemur Posted September 4, 2023 Report Share Posted September 4, 2023 (edited) Do you have roughly 12 volts DC at the fan thermostat input? If not check the rectifier/regulator for AC input and DC output. ... I assume you have a multi-meter or improvised test light Edited September 4, 2023 by lemur Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.