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T-Series 1974 mgb ignition switch/lock w/harness

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mirceme

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My ignition switch is shot and the previous owner replaced it with a simple toggle switch.

I bought a replacement but need to find out how to remove the current lock. It appears to be fastened with some sort of headless bolt.

Any suggestions as to how to back out the old fasteners?
 
Yep, get a small chisel or punch and a hammer and tap them round in the same direction as you would a regular bolt. once you've got them stared they'll usually turn using your fingers quite easily. They're called shear bolts and are there as an anti theft measure.

GavinR /ubbthreads/images/graemlins/england.gif /ubbthreads/images/graemlins/canpatriot.GIF
 
mirceme,

If you have any luck with the chisel routine, than you're more adept at using one than I am. Let me make two other suggestions.

Having recently removed and rebuilt the ignition switch in my 74.5 MGB-GT, I have a pretty good idea about how to remove it.

If you have a Dremel tool, or can borrow one from a friend, than you have the best tool for the job.

Based upon your description, you have removed the steering column covers to gain access to the switch. The "headless" bolts are referred to as shear bolts like Gavin mentioned, but I believe they were used less for anti-theft as they were to facilitate faster assembly. Since the heads shear off at a predetermined torque, they could be installed without having to use a torque wrench. Installers just kept turning untill the head twisted off.

Back to your question...

The bolts are made of aluminum or some other soft metal, and cut rather easily. Install a cutting disc in the Dremel tool and carefully cut a straight slot all the way across the top of each bolt. If you make the cut with a new disc, and cut as deep as you can without cutting the flange surrounding the bolt, you should should be okay.
Using a flat blade screwdriver with a blade width as close to the bolt diameter as you can find, unscrew the bolts.
I used this technique about three weeks ago, and the bolts screwed out easily.

YOU MIGHT NOT HAVE TO REMOVE THE SWITCH HOUSING

If you have a key that fits the "bad" ignition switch, and it still functions with respect to locking and unlocking the steering column, then you might not have to remove the original switch housing.
What you're calling the switch is made up of three basic components: 1- a keyed cylinder (where the key goes), 2- the housing (mounted with the shear bolts), 3- the actual electrical switch (black plastic piece with the wires soldered to it).

If your replacement switch is identical to the original, then you can save yourself some time this way.

The electrical portion of the switch is obviously at the opposite end from the key. Looking at your original equipment switch housing, you'll see a small, number 1 phillip's head screw close to the edge of the housing, at the switch end. Removing this screw will allow you to slide the electrical portion (the actual switch) out of the housing.
The connection between the switch and the ignition key cylinder is a t-shaped male/female interface that will allow the switch to be removed in this manner. At most, you might have to insert the key and give it a little twist back and forth while pulling the switch away from the housing.

With the original switch removed, you can install the new switch just as easily by reversing the proceedure.
Of course, this is based upon your replacement being constructed the same way as the original.

You'll find that the switch's wire harness is taped to the steering column with a wrap or two of black electrical tape, and that the connection is beneath the edge of the dashboard to the left of the column. The connector separates easily, just look twice at the little plastic "levers" on each side to make sure you're releasing them instead of holding them on tighter.

Hope this helps,

Mike
 
Thanks for the help/suggestions.

I was able to remove the shear bolts with a chisel quite easily. The new assembly fit perfectly and had everything back together and working great in a minimum amount of time.

Thank you again
 
How to remove the actual ignition barrel? I am hoping to see a number to get a new ignition key cut, as original key is lost. 1974 MGB roadster with ro-style wheels.
 
Richardspur said:
Where did you cut the slot on the bottom of the lock? Can a chisel be put between the half's and break the shear bolt?
Click to expand...

The slots are cut in the two shear bolts only. The main body of the lock assembly is soft metal, it will be destroyed if split and likely exacerbate the problem. One way to remove the shear bolts is with a drill and easy-out. Another way is a left-twist drill bit. That last will usually unwind the bolts with least effort, the drill will "catch" in the bolt and do the work.
 
mirceme said:
My ignition switch is shot and the previous owner replaced it with a simple toggle switch.

I bought a replacement but need to find out how to remove the current lock. It appears to be fastened with some sort of headless bolt.

Any suggestions as to how to back out the old fasteners?
Click to expand...
I have just replaced my ignition switch, and to remove the headless bolts I tapped them round with a centre punch, once they move they are dead easy to remove. Once I had them out I cut a slot in them with a hacksaw and refitted with a ordinary screwdriver
 
Somewhere I have a tool that was designed to remove and install the so-called "headless" bolts. It is still used today in commercial bathrooms and buildings to deter anyone from removing that type of fastener to damage bathroom equipment etc, haven't seen it in years.
 
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