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MG TD TF 1500 - Suppression Spark Plug Leads

We are having trouble with a recent modification that involves a garage door opener remote control and receiver mounted in the car. When the engine is off it works great. When the engine is cool it is okay. When the engine gets warm it does not work at all. We are treating this like a radio interference problem and have installed resistor plugs and a capacitor to the newly installed device. Still no good when the engine is running. So, now we are looking for suppression spark plug wires.
Where can I find wires that suppress interference and that can still be installed in a stock distributor, ie splaying metal strands around the little copper washers? It doesn't matter if they are already made or just the wire and I can make them to fit. Any suggestions would be greatly appreciated.
Any other thoughts about the problem?
Safety? Fast?
Scott Ashworth - '54 TF
S. R. Ashworth

Try wrapping the receiver in tin foil or copper screen leaving just the antenna sticking out.
Darn, thought you had it solved just by moving it.
What's strange is only happening when engine is hot ...right?
David Sheward

Scott,
Just thinking "way out of the box",,,, have you tried changing the code on the transmitter??? It doesn't seem as it would help, but there seems to be other strange stuff happening,,, maybe if the code was changed, it would not work when the engine is cold!!!

SPW
STEVE WINCZE

Scott - You can't run resistor plugs and resistance wire together without loosing enough voltage to affect engine operation. Cheers - Dave
David DuBois

Just for clarification..you have a transmitter in the car...is that correct? Make the two wire antenna ( usually just hanging out the opener ) a little longer and try to point it towards the nearest window opening (if there is one) between the receiver and the transmitter. Also put a fresh battery in the transmitter.

Changing the dip switch settings may work if it's picking up something else near by but rarely works. If it's a rolling code varity that point is moot. Some receivers have a jumper pin that can be changed to give a better response. That would be the high security setting ( less transmitters used). Depending on the receiver that may not be a available.

I've dealt with a lot of them over the last 20 years. Same models can give a very different range right out of the box. No rhyme or reason other than I think the quality isn't to precise.
L E D LaVerne

I was hoping to post this after I got it working, but more information might be helpful to figure out why it stops working when the engine gets warm.

So, you know how when a deer, or an idiot with a cell phone, darts in front of you, your initial reaction is to slam the center of the steering wheel to sound the horn? And you know how that doesn’t work, ‘cause the horn’s not there? Well, this is what we are attempting to do.

We put a remote control in the steering wheel hub and a receiver tied to a relay and then to the horn circuit. It is a “momentary” remote control which is like a garage door opener, but with these, when you hold the button down, the light, or motor, or in this case, the horn sounds, and when you let up on the button it goes off. It has the same key-chain sender as a car remote control, and a small 2 1/2” square receiver. I found ours on Amazon for about $30. Here is the URL for the unit that we purchased:

http://www.amazon.com/Momentary-Switch-Remote-Control-System/dp/B005CJI6A0/ref=pd_sxp_f_pt#productDetails

The steering wheel hub lends itself very easily to become a horn button. We made a plunger that fit into the MG medallion that pushes the button of the remote control.

I spent a ridiculous amount of time trying to find the best place to put the receiver. I tried dozens of antenna configurations including different antenna lengths, coaxial cables, multiple antennas, parabolic thingies, etc. I could get intermittent horn toots, but not the action that I wanted. The problem seemed to be getting the radio waves out through the metal back of the steering wheel hub such that they could be picked up under the dash. Nothing worked. I was discouraged but not beaten by my overwhelming ignorance ; ). Finally, I gave myself a dope-slap and realized that I could put the receiver inside the back of the driver seat. I don’t recall if it’s the same on TD’s, but on the TF, there are about a dozen pretty screws that hold the back of the seat on. I attached the receiver with Velcro inside the back of the seat with the antenna (1/2 wavelength = 18.75”) attached laterally across what would be the bottom of my chest. I snaked the other three wires out through the bottom of the seat and attached a rubber connector so that I can easily remove the seat. The other end snakes under the carpeting to another connector up under the dash.

Again, it works great with the engine off. It works okay when the engine is running but cold, and then ceases to work at all when the engine gets hot. I have put a capacitor on the power line to the receiver device. I had tried putting the capacitor on the coil, voltage regulator and the generator. I have wrapped the receiver in aluminum foil per Dave S’s suggestion. At a cruise on Saturday we were noticing that some older cars had several capacitors and braided steel sheathing on the spark plug leads grounded to the block. That’s why I am thinking that I need to shield the spark plug leads. We are still positive ground.

It’s a neat party trick just sitting there. But it’s pretty useless if you can’t rely on it when the deer zigs in front of your car.

Any suggestions, yinz guys?

Safety? Fast?
Scott Ashworth - '54 TF
S. R. Ashworth

Picture of the keychain remote mounted to the steering wheel hub.



S. R. Ashworth

Picture of the MG medallion plunger in the hub.


S. R. Ashworth

Action shot.


S. R. Ashworth

Where did you put the filter capacitor?

I should be as close to the receiver as possible, preferably inside and across the 12V lines.

Also since the regulator generates crud over a wide spectrum, including low frequency pulses, it is best to use both a Large value cap, say at least 1 uF and a smaller, rated for RF cap. Say 0.01uF ceramic disc cap in parallel.

Jim B.
JA Benjamin

Thanks, Jim. I put it on the 12 volt line that goes to the receiver. It is under the dash and the receiver is four feet away in the seat. So, I should put the capacitors (both 1uF and .01uf) inside the seat, connected to the power source, in parallel, at the receiver?
S. R. Ashworth

Ok ...now I has better understanding. No solution but a better understanding.
L E D LaVerne

>connected to the power source, in parallel, at the receiver?

Yes that's correct

Jim B.
JA Benjamin

HHuummmm,,,
With all of that electric stuff hidden inside the seat,,, methinks we will have a heated seat very shortly!!!!!!!!!

SPW
STEVE WINCZE

When Scott first contacted me about this my first guess was RF interference from unshielded ignition.
Not a surprise to me at all.
In my early years covering drag racing our TV cameras had big problems with this. Particularly the one at "start line". When the rpm's went up the picture went away from all the rf. If you look at some early coverage ..well that is not a "chrome camera", LOL. Wrapping the tin foil would shield the sensitive electronics making it usable.

The baffling thing to me here is (from talking to Scott) is that this works fine (at any RPM) until the car is warmed up. (about 30 minutes?).
So the challenge (as I see it) is to determine "what" component is causing interference only after "run-in" to operating temperature.

Coil, voltage regulator, or dynamo are only ones I can think of that would do that.

Don't remember ..but have you tried a "separate" 12 volt power supply? Completely isolating the system from all car wiring? Looks like the unit came with 2 remotes. Take the battery out of the one in steering wheel and see it the condition is the same with the other remote.

If it still happens (like we talked about) think I would try coil swap first...it's the cheapest.
Or drive on over and we can swap some parts from Izzy!
David Sheward


Dave:
Your idea of a seperate power supply has a lot of merit.

It needs to go on the receiver (Rx). I dont see the Tx re-sending radiated crud. I do see the post detection circuitry at the Rx picking up the radiated crud and creating errors.

Jim B.
JA Benjamin

Definitely isolated separate power supply for the receiver.
I only mention using the "other" remote as (I'm not sure of this), I think Scott might be "powering" the transmitter from the cars electrical system as well instead of using a battery?
Could be wrong on that one ...but after seeing that it did come with 2nd remote, may as well try the other one.
Been thinking about this one quite a bit since I talked to him on the phone last week.
Keep wanting to point the finger at coil (known problems after "run-in" and getting warm.)
The problem with that theory is he reports no loss of power or other problems with running.
Isolating the entire thing to say a "12 volt jump starter" would be fairly easy to do.
If that system picks up interference after run-in then we definitely have a RF problem somewhere.

I'll have to dig around in some boxes and may still have some copper mesh.
Years ago I delivered a TV remote truck to Kentucky University. One venue they worked in (on regular basis) they would get RF interference through the audio patch panels in the truck every time.
I solved that problem by surrounding the "rack" the patch bays were in with a grounded copper mesh that blocked the RF interference.
Basically it looked like a fine copper "screen".
David Sheward

I did put in a new coil. - No difference. (I now have three coils and three sets of plugs. Will never have to buy those again!)
The key-chain sending unit is run from its own internal battery. The bed in the hub is designed to allow easy access in order to change the battery, and just as a shot in the dark, I did put in a new battery. - No difference. (The unit that I bought a couple years ago only had the one remote sender.)
I will definitely try a separate power source. As you say, it will be pretty easy to do. If that works, I would look for a smaller 12 volt battery that would power the system, since all it has to do is operate the receiver and trip the relay.
I do want to try the two-capacitor fix that Jim mentions, first.
I really do appreciate the thoughts you guys are coming up with.
Safety? Fast?
Scott Ashworth - '54 TF
S. R. Ashworth

Electrical interference can get quite frustrating, especially when you haven't a clue where it's coming from. Not that it's related to your situation, but an example of an experience I had the other day. Out at the airport using airport transfers tonbridge with my son, I was talking to him while he was in flight on my hand held radio from my truck and the static was awful! He told me my transmission to him was weak and over modulated. I found out by accident that my cell phone was plugged in to the truck for charging and when I unplugged it all the static in the radio ceased and it transmitted perfectly. Strange, but you never know. PJ
Paul sr

> do want to try the two-capacitor fix that Jim mentions, first.


Another thing that may help.

If you can find a ferrite core, be sure the power leads are twisted their full length, then loop them through the core several times, just at the Rx.
This helps with HF crud but is not effective at lower frequencies.

Jim B.
JA Benjamin

Wouldn't it be less aggravating to just change the garage door openers frequency? PJ
Paul sr

All the thinking in this thread is that, as the engine is heating, up something in the RF electronic transmission/switching kit is preventing the electronic communication facility from operating the horns.

To be honest, I just don't get it! RF radiation is not affected within the automotive heat range, but it is by water vapour (which I suggest is also not part of the problem, sorry).

So, my suggestion is that it is something in the wiring between the RF receiver and the horns. Here expansion from heating could be affecting the connections. Check the resistance of these wires when hot.

Well, maybe ... !

Ian Bowers

Good point Ian!
Also good one from Jim about twisting the pairs.
I have tons of "twisted shielded cable" we could try as well.
It is fairly small gauge, so may require moving the relay closer to destination (horns).
I'm sure a have a few "chokes" about as well!
(ferrite core)

Paul,
Problem does not seem to be frequency dependent as it works fine (at any RPM) until the car warms up for about 1/2 an hour.
David Sheward

I'm wondering if the noise is coming from the control box. When it's first running your'e probably getting a steady charge to the battery. Once charged, it's now bouncing on and off. Maybe generating ( via the dynamo) some weird frequency. I think if I were to have a go at it I'd try some foil (probably dynamat) on the inside of the fire wall and toe board as a shield from the engine compartment.

As a test ..you could run the engine up to the point where the transmission fails. Remove the fan belt and fire it up and test again. If it doesn't fail you know that the problem is somewhere in the charging circuit. If does fail then that's a source you can eliminate.

Doesn't take a lot to cause havoc with garage door frequency signals. Most won't work on high end vehicles as the signal won't go through the gold sheet laminated into the glass. You have a relativly short path from the seat to the steering wheel. So thats not an issue.

One other thing I would check is the relay your'e running the horns off of. I'd check when you have a failure ..the receiver leads ( with a meter) and see if it shows continuity when pressing the horn. Possibility the relay may require a stronger source when warmed up.

Just some random thoughts.
L E D LaVerne

>All the thinking in this thread is that, as the engine is heating, up something in the RF electronic transmission/switching kit is preventing the electronic communication facility from operating the horns.

>To be honest, I just don't get it! RF radiation is not affected within the automotive heat range, but it is by water vapour (which I suggest is also not part of the problem, sorry).
>

Ian;
Try this for a reason.
The regulator on an MG is a current regulator. It vibrates and in effect pulse width modulates the duty cycle of the generator to control the current.
A cold battery has a higher terminal voltage than a worm battery.

As the battery heats up, the regulator has to vibrate different than when its cold.
Could this be the Issue?
I dont know but it is a hot/cold difference.

Jim B.
JA Benjamin

This kind of fun....amazed someone hasn't suggested large "red arrow" on wheel center ...pointing to horn button on the cowl yet! LOL

What I love about this group ...we relish a challenge, and the more beer we drink ...the more ideas we come up with!

Cheers,
David
David Sheward

Thanks you guys.

I have a bunch of stuff to try. In order of ease of accomplishment:
A separate power source.
Check the relay.
Two capacitors at the receiver.
Re-route my small harness away from heat.
Ferrite core - (much googling to understand).
Big red shewardian arrow.

By the way - and sorry for the incomplete disclosure - but I do have a solid state voltage regulator. One of the reasons for getting that done was for this receiver - thinking it might need a more consistent power source. But I would have done that anyway.

Lot's to try. But British Car Day is on Saturday in Pittsburgh, so follow-up on this may be on hold until after some polishing, Q-Tip-ping and Armour-All-ing.

Thanks again for your time and thoughts.

Safety? Fast?
Scott Ashworth - '54 TF
S. R. Ashworth

Ferrite core - (much googling to understand).
Don't bother, I can send you one, and a picture if we go that route! I'm sure you have some electronics around that have these on/in them!

Armour-All-ing! NOOOOOOO please don't use that stuff on your car!

HATE IT
HATE IT
HATE IT

IMHO: Makes plastic & vinyl hard and brittle, turns rubber orange & dull if you don't continue to use all the time. I can't for the life of me understand how they still sell that crap!

Use Mequires ...but never Armour-All!
I'm not a fan of "shinny-fly-pimp-tires" ...but I use the Mequires stuff in the fall when the car will be sitting most of the winter. Keeps the tyres looking new and the rubber supple. Face it ...most of us get quite a few years out of tyres on these cars as they don't get driven daily.
David Sheward

Jim B

Good thoughts, but surely the frequency of the mechanical regulator oscillations is way below RF. And that has now been excluded.

My real point as that RF is not heat sensitive in tte way that it is water vapour sensitive.

Hopefully the problem in on its way to solution
Ian Bowers

>Good thoughts, but surely the frequency of the >mechanical regulator oscillations is way below RF.

The opening and closing of the points creates a pulse with a very sharp rise and fall.

Those, raise and fall times, can only be accomplished by having frequency components well into the RF spectrum.

There is a mathematical/engineering "thing" called a Foureir transform. It is used to map the frequency components of an arbitrary amplitude/time wave shape. At the rise and fall times increase the higher frequency components must also increase.


(Google "fourier transform" but the math is high level)

Mercury wetted relays are used to generate impulses with frequency components well into the GHz region. I would guess the regulator would generate crud into the AM broadcast band.

Now as you suggest the problem may not be RFI but I have seen similar issues with digital equipment near RF noise generators.

Jim B.
JA Benjamin

Having reviewed the product description, and the feedback from other purchaser, here are some thoughts:

1. As an experiment, try to power the receiver with a 12 volt battery, not from the car's power. That will help you eliminate whether transient RF is coming through the power feed wires, since they can act like antennas.

2. The feedback on the product included comments about limited range. So try moving the receiver in closer proximity to the transmitter and see if that helps, as an experiment.

3. The MG steering wheel hub may have a metallic coating under the paint. If so, it may be shielding the transmitter signal.

4. As the coil gets hotter and the condenser (capacitor in the distributor) gets hotter, their values do change. One sign of a capacitor that is about to fail is that the car starts fine and then breaks down when hot. So their RF output does change when hot. The coil has oil in it that changes temperature, and the condenser (capacitor) also changes value when hot.

5. Here is where this gets tricky. If you wrap components in metallic screening wire (copper, etc.) or aluminum foil, you are creating a Faraday shield to RF. At the same time, you can be blocking your signal. While the receiver may be picking up harmonics from the power source, shielding that out may be difficult if the charging system is the source. A capacitor on each side used to be fine for radios in old cars, but you are looking for a specific digital frequency, and it may be overwhelmed and the receiver may not be very discriminating. What this is doing to your receiver in terms of changing it's performance is not clear. Plus, you want a reliable system. Having lived in PA, your reaction time for deer, etc. is crucial.

So, I would opt for a hard-wired system. Why not tie your horn button to your steering wheel button and go with a non RF solution?

Best,

Ira

Ira Spector (PA)

This thread was discussed between 13/07/2013 and 21/07/2013

MG TD TF 1500 index

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