CtrMint Posted February 21, 2019 Share Posted February 21, 2019 Guys, I'm still struggling to get my radiator fan on. I've had the car up to 108c according to my OBDII tool, though Derek @ CC disputes this will be accurate. I'm not entirely convinced with that, in my experience if a protocol can be negotiated and read, it's going to be as intended.Assuming Derek is correct and my reading is too low I should let the car get hotter, however, I'm just not comfortable with that, its nearly at the red on the analogue gauge anyway!I'm therefore left to check for electrical issues.I've checked the loom plug which connects to the radiator, its grounded on the black wire, open on the other, which seems correct.I've checked the relay operation with a bench supply and its switching OK.I'm therefore considering the connection between the low and high current side of the relay might be an issue. Is there a trick to test continuity of relay connections within the fuse board..I'm thinking I need to check continuity between; Relay low current side to ground and ECU signal pin (not sure which it is yet) Relay high current side to ground and also fan connector positive.I don't want to insert a round probe from my meter into the flat receivers on the fuse board, is there a special diagnostic insert I can use for this?Sorry never done this sort of work before. Link to comment Share on other sites More sharing options...
MADMALC Posted February 21, 2019 Share Posted February 21, 2019 Have you put 12 volts directly to the fan to test that it works?Are you confident that the thermostat is opening? Both top and bottom hoses should be very hot. Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 Most blade fuses have small contact points on the top that'll enable you to measure there without removing them. You can then measure across to see if they're blown and you can measure to earth to see it's live.Which ECU does your car have? I am not sure I have the correct wiring diagram - or would you be able to email the correct one to me? I appreciate that the format nowadays is a bit different but as wires have numbers etc I trust I can navigate across it. Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 Madmalc, Yep fan is fine, tested it with a bench power supply. Pretty confident the thermostat is fine as all the hoses are getting very hot. Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 RJ, I'm confident the fuses are fine, its the relay circuit I was looking at, but I guess you are saying check the fuse to the plug right?Sorry not sure on the ECU, and I don't have a wiring diagram. I was going to try and look at the wire colours.... Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 What is in your build manual with regards to electrics? Do you have the build manual in PDF or just as a hardcopy? Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 CC only sent me the Ikea manual which is useless as it only covers Sigma cars, and I have a 420. I have sourced an electronic copy of the 2015 manual but I don't believe it is entirely up to date.Derek sent me the following diagram in response to one of my queries, it suggests I have a 620 loom... who knows. Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 Wonder if any of this will cover your car?www.regins.dk/Caterham/diagrams_2015.pdf Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 Beaten to it. Does the relay have some sort of numbering on it?30 would normally be the +ve feed and 87 the output - there's a chance that the +ve is always on and that it's a swiched earth in wich case I'd expect 30 to be earth in the socket.The output of the ECU would be switched earth.Can you post a picture of the ECU or at least the connectors to give me an idea of what we're talking about? Link to comment Share on other sites More sharing options...
Ivaan Posted February 21, 2019 Share Posted February 21, 2019 The relays are cheap as chips. Buy a spare and try it. Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 Ivaan, I've tested the relay it seems to work fine. Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 What colour wirer are connected to the fan? Is there only one fan? And colours to the relay? Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 "Which ECU does your car have?" I've pulled the battery out and unclipped the PCM and separated it, ECU appears to be 30L279AAll the cabling around the plug seems fine. Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 https://caterhamparts.co.uk/ecu/5822-ecu-9a4-he.html Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 The fan is connected with an alternator style T plug, one wire is black the other black/green.Still trying to work out the relay colours. Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 I've removed the fuse/relay box at least one of the connectors was completely loose, black/green into the relay!! I wonder if that is it. I could do with photo of the correct configuration. Link to comment Share on other sites More sharing options...
PeterM Posted February 21, 2019 Share Posted February 21, 2019 Have you bleed all air directly from the top of the radiator? Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 Yes, pretty confident we got all the air out last weekend, Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 Can't help you with a picture as I don't have a 620R to hand and here there's no such thing as a 420(!)That said it sounds like the black / green has to go in as marked with a red arrowI would also expect the one marked N 29 to be a +ve feed and therefore if you short this and the black green the fan should come on.I doubt it's an airlock in the rad as I believe the rad is controlled via the ECU - or is there a thermoswitch in the rad? Link to comment Share on other sites More sharing options...
rj Posted February 21, 2019 Share Posted February 21, 2019 Aaah.That does not look right. Remove the relay and re-insert the terminal. Link to comment Share on other sites More sharing options...
ChrisC Posted February 21, 2019 Share Posted February 21, 2019 My bet is the connection between the ECU and relay. I suspect the software / ECU is fine, or we would have 420s over heating all over the place. It's been know for the pins not to be seated properly in the ECU connector, I wonder if that the case for your fan control wire from the ECU. If you have tested the relay, fan, fuse and the continuity between the fan and the relay, the continuity with the fan and earth, then it would be next on my list. Link to comment Share on other sites More sharing options...
ChrisC Posted February 21, 2019 Share Posted February 21, 2019 oh just seen the photo, yep that looks wrong Link to comment Share on other sites More sharing options...
CtrMint Posted February 21, 2019 Author Share Posted February 21, 2019 Put all the battery and stuff back in, shorted the high current side connections in the fuse block and the fan kicked in.The cable which was out I believe is the low current side from the ecu, Link to comment Share on other sites More sharing options...
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