red light

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dougi
Posts: 74
Joined: 24 Jun 2006 18:34
Location: north east england

red light

Post by dougi »

the red light on my 1978 3-1/2 sport stays on when the engine is running. is that ok ? if it is ok why is it on when its running ?
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ringer
Posts: 81
Joined: 19 Jul 2008 11:38
Location: Northampton

Post by ringer »

Assuming you have checked the connection of the wire on the oil pressure switch, have you tried disconnecting the wire from the switch and measured the resistance of the end of the wire to earth? If the wire is damaged and shorted to earth then that would result in your symptoms. Otherwise buy yourself a new oil pressure switch - compared to a trashed engine it is much cheaper and easier to fit.

Nick
dougi
Posts: 74
Joined: 24 Jun 2006 18:34
Location: north east england

Post by dougi »

i have,nt checked the wiring yet. i did,nt think morini 3-1/2s had oil pressure switches ?. i am now thinking it is to do with the battery charging system,when the red light is on it is not charging the battery?
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ringer
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Joined: 19 Jul 2008 11:38
Location: Northampton

Post by ringer »

All combustion engines should have an oil pressure switch. There is an electrical circuit which starts with 12V sourced from the battery, connected through the red idiot light, along a wire that goes down the front left-hand tube of the frame and to the oil pressure switch which is located on the underside of the LH crankcase cover near the front. When there is no oil pressure - i.e. no oil being pumped around - this switch creates a connection to earth which completes the circuit and so the red light comes on.

In this picture, follow the wire that goes down to the bottom of the front tube of the frame and then back up slightly underneath the LH crankcase cover. That is where the switch is, where the wire is connected.

Image

When you first switch on the ignition the engine is not working and so there is no pressure in the oilways. Hence the red light is on because the light is connected to earth. When you start the engine and it is running, the oil pump pumps the oil through the oilways and past the pressure switch which detects this pressure and stops the connection to earth which breaks the circuit and the red light goes out.

If your engine is running and the red light is on THIS INDICATES A BIG PROBLEM. Either there is insufficient oil in the engine or you have an electrical problem with the wiring to the pressure switch. Have you checked the oil level or condition of the oil in the engine recently? Whatever your answer DO NOT RUN YOUR ENGINE until you have established why the red light stays on.
hendre
Posts: 600
Joined: 11 Aug 2007 06:51
Location: The Netherlands

Post by hendre »

have to agree with dougi.... early Morini's did not have a oil pressure switch. The red light indeed had something to do with the charging circuit. :!:
George 350
Posts: 450
Joined: 16 Jun 2007 09:43
Location: Northampton

Post by George 350 »

Red light:
Prior to the electric start models, there was no oil pressure switch on Morini's - I recall it was introduced with the 500 in 1978 (4 warning lights), and then on the 350's later.
On non electric start models this light simply served notice that you had turned the ignition on (as if the clunk of the fuel tap didn't tell you that). If it went off, either the battery was flat or it had blown.
If it annoys you, simply take the bulb out (or wait for it to expire).
When I rebuilt mine 10 years ago I made up a new wiring loom from sctatch and I modified the circuit so that the light became a charge warning light - on = no charge, off = all ok.

George.
George
350 sport 1978, 350 Strada 1978
650 Norton 1967, 650 Kawasaki 1977 and 650 Enfield 2019
Vitesse
Posts: 218
Joined: 05 Jan 2019 13:42
Location: Barnacle
Location: Crowcombe

Re:

Post by Vitesse »

George 350 wrote:Red light:
Prior to the electric start models, there was no oil pressure switch on Morini's - I recall it was introduced with the 500 in 1978 (4 warning lights), and then on the 350's later.
On non electric start models this light simply served notice that you had turned the ignition on (as if the clunk of the fuel tap didn't tell you that). If it went off, either the battery was flat or it had blown.
If it annoys you, simply take the bulb out (or wait for it to expire).
When I rebuilt mine 10 years ago I made up a new wiring loom from sctatch and I modified the circuit so that the light became a charge warning light - on = no charge, off = all ok.

George.
If I'd done my search first I wouldn't have had to ask you George!!!!! :D
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