Electrical problem.

Technical advice Q&A

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dxke38
Posts: 113
Joined: Sat Mar 10, 2012 8:13 pm
Location: norfolk
Great Britain

#1 Electrical problem.

Post by dxke38 » Thu Apr 01, 2021 6:08 pm

Hi guys, just wondered if one of you electrical wizards could help me with a real problem. I'm trying to help a friend with an issue on a Ser 2 American import that he is restoring. He has fitted new wiring looms, new upgraded cooling fans and relay and otter switch, also new 4TA regulator and ign warning light unit. The car starts and drives fine but the ignition light pulses on and off. When the engine reaches temp and the fans come on the ignition light goes out but the terminal on number 6 fuse that feeds the fan supply gets hot and has started to melt the fuse block. I have checked the wiring and connections and cannot see whats wrong. I thought it was a fault with the fans but now think charging circuit? Any ideas gratefully received. He has driven the car but gave up when the smoke from the dash appeared.
Derek
64 ser 1 fhc, 71 ser 3 2+2.

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mgcjag
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#2 Re: Electrical problem.

Post by mgcjag » Thu Apr 01, 2021 6:32 pm

The upgraded fans possibly draw more current than the originals so will probably need a seperate supply rather than just useing the original......whats the spec of the fans....is the new loom just for the fans...or general wireing loom....Steve
Steve
69 S2 2+2 (just sold) & Building a C type replica

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christopher storey
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#3 Re: Electrical problem.

Post by christopher storey » Thu Apr 01, 2021 6:36 pm

The key to this is almost certainly the "upgraded" cooling fans. Some of these can take up to 25 amps per fan, and if current like this is flowing through a standard loom then you are lucky that you have not had a fire . There is no easy solution, but the first thing I would do is to put the original fans back on - on an S2 they are perfectly adequate if the cooling system is in good condition . The other thing is to use relays where possible, which shortens the lengths of loom wires subject to excessive current . The moral to this story is that a great number of "upgrades " ( how I hate that word ) are in fact downgrades

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Topic author
dxke38
Posts: 113
Joined: Sat Mar 10, 2012 8:13 pm
Location: norfolk
Great Britain

#4 Re: Electrical problem.

Post by dxke38 » Thu Apr 01, 2021 8:11 pm

Thankyou for the prompt replies guys. I did at first think the fans were the problem, they are the usual fan and cowling set from SNG, but the Ignition light issue with it pulsing on and off sidetracked me into considering other reasons. Also if I bypass the otter switch and run the fans without the engine running, the fuse holder doesn't get hot. The wiring loom is standard and all relays are new. If I fit a separate supply with a line fuse, where do you suggest I get the feed from? Been checking this problem out most of the day and now can't see the wood for the trees.
Derek
64 ser 1 fhc, 71 ser 3 2+2.

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mgcjag
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#5 Re: Electrical problem.

Post by mgcjag » Thu Apr 01, 2021 9:54 pm

Hi Derek...i have no idea what the "usual Sng fan upgrade" is....you need to check if it uses existing wireing or it needs an upgrade.....the ignition lamp could be tbe 3AW/alternator/regulator.....you need to break the problem down....disconnect the fans then fix the ign lamp problem and ensure all other electrics work.......then after checking whats required for the fans re install them......Steve
Steve
69 S2 2+2 (just sold) & Building a C type replica

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