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Glow plug relay not working


Karen Lea Rainey

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Hi All,

I have a BMC 1.8 engine that I believe the glow plug relay has given up, measuring no voltage at the actual glow plugs and after taking a glow plug out to do a battery heating up test , I surmise that it's a relay problem. Having taken the relay off, I can see no markings on the unit except for what could be a production date 021015 or serial number?

My question is where can I get a replacement relay? Can I use a universal  relay akin to Durite etc or do I need to buy an expensive land rover relay etc,

Pictures attached to help, I would be grateful for your help.

20180917_061032.jpg

20180917_061055.jpg

20180917_061117.jpg

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It is a simple rather old fashioned car starter solenoid. You do not need one with the two small blade terminals because it is easy to get them wrong and almost certainly one on yours should not have a wire on it. Before you buy new make sure the metal body has a good negative connection and that the wire from the ignition switch or glow button goes to the single 6mm blade. The even smaller one is to do with a car's ignition  circuit. A wire from the master switch and the wire to the glow plugs should connect to the two studs although you can  use the   9mm blade that is on one stud. I would expect any Motor Factors or Halfords to stock one. The part number is unimportant as long a sits for 12V.

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Out of curiosity why is a relay necessary?

 

Just to reduce current that has to pass through the starter switch?

 

I ask, because when we had a BMC 1.8, the heater plugs wrre simply wired direct to the starter switch - there was definitely no relay on our one.

Edited by alan_fincher
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I get these from AES, Auto Electrical Supplies.  Although I have no heater plugs, but I use one for my starter motor as I use an ordinary ignition switch from an old petrol engine car.   You can get them with a manual push button on them too, so that if the heater contacts in the starter switch fail you can heat the plugs at the solenoid by hand.   They were in fairly common use as relays on some older boats as an extra one as well as the pre-engage starter motors solenoids to protect old type ignition switches.

Edited by bizzard
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1 hour ago, Tony Brooks said:

It is a simple rather old fashioned car starter solenoid. You do not need one with the two small blade terminals because it is easy to get them wrong and almost certainly one on yours should not have a wire on it. Before you buy new make sure the metal body has a good negative connection and that the wire from the ignition switch or glow button goes to the single 6mm blade. The even smaller one is to do with a car's ignition  circuit. A wire from the master switch and the wire to the glow plugs should connect to the two studs although you can  use the   9mm blade that is on one stud. I would expect any Motor Factors or Halfords to stock one. The part number is unimportant as long a sits for 12V.

Motor factors and Halfords would probably have to order one in these days Tony.

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1 hour ago, alan_fincher said:

Out of curiosity why is a relay necessary?

 

Just to reduce current that has to pass through the starter switch?

 

I ask, because when we had a BMC 1.8, the heater plugs wrre simply wired direct to the starter switch - there was definitely no relay on our one.

It all depends upon the conductor cross sectional area and length of the cables. On a typical narrowboat without any idiot multi-plugs and with a "diesel" specified switch then probably no, but as soon as you start increasing the cable length without increasing its CCSA then yes a solenoid or relay is likely to be required. A forward control, engine close to the stern boat then to save wiring costs the answer is almost certainly yes, one is required.

 

You can also use one to cover up doubtful contacts in the ignition switch but that is a bodge.

 

 

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33 minutes ago, bizzard said:

My ignition starter switch is an old Lucas one from an Austin A40 Farina and uses the nice neat little FP keys, I still have two more in stock with the FS keys, remember them?

Yes, and some more key letter prefixes. We had a great length of welding rod in a loop with loads of keys on it so we could usually find one to get into a customer's car when the lost the key or locked it inside. At least you can change the barrel on your switch if your security becomes compromised.

 

To the OP.

 

If anyone offers you a barrel shaped one then it is wired just the same and will do the same job, just a rather older design than the one you have  except it may have a screw connection for the cable from the switch..

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13 hours ago, bizzard said:

My ignition starter switch is an old Lucas one from an Austin A40 Farina and uses the nice neat little FP keys, I still have two more in stock with the FS keys, remember them?

 

Yep. 

 

And each would fit in the other door lock and ignition once adequately worn....

 

This is how my A35 got nicked from college and I accidentally got into another identical one mistaking it for mine, and drove it a mile wondering why everything seemed slightly different before figuring out my error!

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