MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - What is this & Dash Clock

Ok what is this I am looking at. I am in the process of installing a new wiring harness from Advanced wire on my 79 MGB. While removing the old wiring I came across a small component that I am not sure what it is. It is mounted to the side of the original fuse block and looks like a voltage regulator. It is aluminum, about 2 inches square and the top has fins like a heat sink.

BTW I pulled the Dash out yesterday and it is not as hard as I have herd. The one nut above the Speedo and Tach was kind of hard to get to but beside for that it was not a problem at all. It only took me about 1 hour to get it completely out.

Speaking of the dash I am replacing all the gages with newer ones. The one thing I can not find is a clock to fit the round hole the old clock was in. I was going to purchase SUN gauges but am willing to look at anything as long as I can get a clock also. I need a matched set so I can not use a original clock.

Any ideas?
bsf Fowler

I'm guessing you have a 1977-80 MGB....that is most likely part of your electronic ignition...was is under the coil?

rick
rick ingram

Yep 1979 MGB.

The coil is upside down on the right fender. The component I am talking about was above the coil next to the fuse block all the way at the top of the fender under the lip.

The car had points originally and this component has always been there. I switch it over to a Malloy pointless disruptor a long time ago.
bsf Fowler

bsf. No, your car did not have points originally. Originally, the car was equipped with the Lucas 45DE4 (Opus) electronic ignition system. The one on my 79 (purchased in 79) went out within the first four months of ownership and was replaced under warranty.

Owners who were unfortnate enought that their systems lasted a little longer found that there was no, or very little, factory warranty support left--MG was out of business. Hence, at some point, your car was fitted with a points type distributor. It may have also, at some point in the last 26 years, been fitted with an aftermarket "electronic ignition". My daughter's car had a Luminition system fitted to the Lucas 45DE4 externals. This system seems to have run well for about ten years, at which point it became unreliable and was replaced with a new Lucas 45D4 points type distributor.

So much for history and why you may find things on your car which differ from "factory standard". With the Lucas 45DE4 distributor, a resistance wire was used to provide full time 6V (actually 6-8V) to the coil when the ignition switch was in the "run" position. The coil received temporary 12V input, from the starter solenoid, when the starter was engaged. (Hence the two wires going to the input side of the coil.)

The Lucas 45DE4 electronic module needed reduced voltage input at all times. Hence, it was wired through a ballast resistor which is about 3/4" wide, by 1/2" tall, by 2 1'2" long. It is black and silver in color and seems to have cooling fins on the examples I have examined. This might be the item you are describing. It is generally located in front of the coil and behind the fuse box, slightly below uppermost portion of the coil.

If it is not the electronic ignition ballast resistor, it is part of the remains of some form of aftermarket electronic ignition system and is the power module board. These are normally about 3"x4", made out of aluminum with heat sink fins machined in and may have one or more semiconductors visible on it.

In any event, neither of these items would be used with your car as currently configured.

Because neither of my descriptions fit the item as you describe it, there is one other possible thing it might be. In front (towards the front of the car) of the fuse box is the ignition relay. This is, normally, a round, black object about the size of a 35mm film can. It is attached to the inner fender, by a single screw, through an L shaped bracket which is attached to the upper end of the relay. On the underside are four wires which allow the "white wire circuit" to be energised when the igntion switch is turned to the run position.

If you do not have a copy of the wiring diagram for your car, you need one. Wiring diagrams may be available at your local library and list member Dan Masters has color coded wiring diagrams available on his website. (Look in the archives if Dan does not post the site to this thread. I believe the title of his tread was "Color Coded Wiring Diagrams".) Make a copy of the wiring diagram. Take it to a copy shop and have it expanded 300%, making it far more readable. I have mine laminated so that I can draw on it with a water soluable marker.

If we have not correctly identifed your part, please let us know and we will try some more. I have given you the three most probable answers.

Les
Les Bengtson

I vote for the ballast resistor theory.

rick
rick ingram

OK that makes sence Yes I did find the ignition relay.

The component has 5 wires connected to it. Per the diagram form DAn it looks like the starter relay.
bsf Fowler

Found it on the proper MG web site. You where correct it is a part form a MGB Lumenition Electronic Ignition Kits. The one on their page is identical to what i have.

Thanks for your help
bsf Fowler

SO that brings up another question. Where is the starter relay and what does it look like?
bsf Fowler

I've never seen a finned relay before, but that doesn;t mean there is not one made. Typically the Lucas relays are round canister looking devises with prongs on the bottom. They are about the size of a 35mm film canister. Bosch after-market relays are a little over one inch square and high with prongs on the bottom.

On my 1978 MGB, the ignition relay is on the right side inner fenderwell a few inches back from the radiator surround, and the starter relay is located about where you are describing.

If I can get out to the barn tonight, I'll take a photo and send it to you as an e-mail attachment.

rick
rick ingram

bsf. The starter and ignition relay are the same basic part. The ignition relay is located forwards (towards the front to the car) of the fuse box. The starter relay is located to the rear of the coil. Either may have been replaced with a non-Lucas unit over the years and may have a different shape that the Lucas 35 mm "film can" style.

Les
Les Bengtson

bsf and Les...

I sent you a bmp file of the parts in question...

rick
rick ingram

Rick. Many thanks, but the Aztec server is text only. However, your written description was clear enought that bsf should have no problems looking at your photo and figuring out the positions of the relays. Unless, he, too, has a text only server.

Les
Les Bengtson

Thanks all. The BMP did not have the part in question in it. I think it was a part for the ing. I found the 2 relays with help from the BMP.

I also found a number of clocks to go in the dash from Autozone.
bsf Fowler

Glad I could help.

rick
rick ingram

I was looking at the diagram I received form Dan when I purchased the wiring harness and the "Power Block" comes with a starter relay and a Power(IGN)Relay.

I have printed the diagram out on my Plotter so I have a 34 X 44 diagram hanging on the wall I am going to trace out as I do the wiring.

The more I look at this diagram and the harness the more I like it.

This weekend I finish gutting out the rest of the old wiring and mount the Power Block. Since the carbon canisters where removed a long time ago I a thinking of mounting the Power Block there.


Thanks
Bob
bsf Fowler

Dan makes a great wiring harness. I have one for the MGB/V8 that he custom-made for my needs for that car.

I've seen power blocks mounted in the concave area in the firewall behind where the carbon canisters sit on your MGB. One owner even covered the box with plexiglass.

Wherever you put it, make sure that it is accessible.

FWIW

rick
rick ingram

bsf
I put Dans harness in my1979 B V8 conversion last spring and it is just great. I installed my power block under the
glove box as I wanted to get it away from the heat in the engine compartment.This is probably not a concern for you though.I have found its not in the way and changing a fuse is a bit challenging but the indicator fuses Dan supplies glow if they blow so its easy to figure which one blew .My lights are brighter and you can acctually read the instruments now with better power flow.
just my 2 cents
Gil
Gil Price

Regarding the clock. Since just about every car radio/CD/cassette player has a clock incorporated in it. Why not put a voltmeter or vaccumn gauge in it's place using the same brand as the other instrumenta ? Barrie E
Barrie Egerton

I am in the process of installing Dan Masters wiring harness into my BV8. I had first mounted the power block on the shelf above the passenger footwell, but then reinstalled it on the side of the passenger footwell where it can be covered by the map pocket( with little modification). I was very concerned about protecting it from potential damage which could be caused by it being kicked or hit when having passengers with work boots etc. After having devised a cover for it, it just reduced the clearance more. I found that the wire routing worked better here as well. Just my two cents.
Dave B .
David B

As far as the clock goes This is actually my Ol'Ladys car and she wants a analog clock in the same place it was before. I tried to talk her into letting me put something else there but she would not have it. I am buying a new dash so I may experiment on modifying the old dash to see if I can fit another round hold big enough for a volt gage. I am not sure about this though. It has to look good also. I am at work now and can not see the dash to tell if one could be added.

I was looking at the diagram and instruction I received form Dan. In the instructions it states that when the fan is off and the car is going down the road the wind may turn the fan making it act as a generator and light the fan indicator light. Couldn't I just put a 12v 20a diode in line with the fan to stop any back voltage?

Thanks
Bob
bsf Fowler

"Couldn't I just put a 12v 20a diode in line with the fan to stop any back voltage?"

Bob,

You could, but I don't recommend it. There is a big difference in the brightness of the lamp when the fan is on, and when the fan is acting as a generator - you won't mistake one for the other, so I find the dim light to provide a positive indication that everything is working as it should. Adding a diode just adds one more potential trouble point and drops the voltage to the fan just a bit.

If you prefer to add a diode, though, Just excercise care in locating the diode to keep it as much as possible away from any heat source under the hood - inside the car would be better.
Dan Masters

Makes sense. If the lit is dimly lit I will know the fan is turning because of wind. If it is brightly lit I will know power is getting to it.

How about placement of the power Block. Does the location where the carbon canisters where sound good.They have been removed. I do not think it will get wet there and it is a nice flat area with access to several holes to route the wires into the car. I was going to but it under the glove box but I am worried about someone kicking it when they sit in the passenger seat.
bsf Fowler

Bob,

There should be no problem mounting the panel there as long as no water drips on it. I'v mounted the panel in my TR6 in the same location.

I prefer an inside mounting, but under the hood is no problem - I've run these same type relays and flashers under the hood for years without any trouble at all. I mounted mine under the hood just for advertising purposes - I want people to see it when I open the hood, hoping they'll ask about it and I can make a sale.
Dan Masters

Well there is no room for another gauge so I talked my Ol'Lady into giving up the idea of having a clock. Like someone said she has one on her radio anyway. While I had the dash face out I cleaned up everything. Ran new heater ducts and washer hoses. I striped the dash, sanded it and painted it black. Looks good that way. This coming weekend I will repair the wipers. They are moving real slow for some reason.

Any ideas why?

I decided to mount the Power Block where the carbon canisters where. But the area was to short. SO I took some 16ga steal and made a mounting plate for it. Worked real well.

Bob
bsf Fowler

Les, replace the grease in the wiper motor gearbox. The old stuff has most likely turned into stone by now. Baerrie E
Barrie Egerton

Dear Barrie. 'Twas not I that mentioned a problem with the wiper motor gearbox. However, since you mention it, I do remember having said problem the last time I drove my car in the rain. (About two years ago--we have been in a drought situation for several years here in the desert.) With your reminder in hand, I will put it on my list of things to check out and correct this winter. Like you, the normal "winter" time is our better time of the year.

By the way, my younger daughter, along with two of her girlfriends, just spent four days in Fiji (Maria and one friend), then about a week in New Zealand (where they picked up their other girlfriend who was attending University there for one term), then a couple of weeks in Australia. Could not eat the food in Fiji. Was not impressed with the lack of spices in the food in OZ and NZ. (But, Katie, having lived five months in NZ, knew the best beers.) Overall, they had a great time in NZ and Oz and mentioned seeing a number of MGs while there, mostly chrome bumper models.

Thanks again for the tip. I will remove the wiper gear box, clean it throughly and re-lubricate it. Then, we will see how it works.

Les
Les Bengtson

Slow wipers are very much chicken and egg. Any mechanical drag causes higher than normal current to flow, which causes more volt-drops in the long runs and many connections, hence lower voltage at the motor. Any bad connections in the 12v and ground supply to the motor will cause lower voltage at the motor, which will cause it to run slowly!

Mechanical drag could be very hardened grease in the gearbox, stiffness of the rack and tube if the tube has been crimped or bent, or stiffness in the wheel boxes. There is a lot of mechanical drag even in good systems, so it is difficult to decide where the problem is, disconnecting parts of even a good system will cause it to run faster anyway.

Volt-drops could be anywhere in the green circuit which is pretty notorious anyway. There are volt-drops even in a good system, and even if the problem is mechanical supply more volts direct at the motor e.g. with 'jump' leads direct from the alternator or a good battery will make the motor run faster even on a system with no bad connections.

You could easily have two or more problems which are contributing, i.e. no magic bullet, but attention to several things could all help.

And finally, slow when compared to what? At their best they will almost certainly be slower than a modern car.
Paul Hunt 2

Thanks all

Since I am re-wiring the car with one of Dan's wiring harnesses this should take care of the electrical side.

BTW Dan has been a great help with this. I had a few questions about it and he answered me right back.

Anyway I will go through the wipers, check the mechanical side and clean and re-grease the gearbox, tube and so on. I see form the archives that whit lithium grease has been used. Is this still the recommended grease?


Thanks again
Bob
bsf Fowler

bsf

Regarding you being surprised with how easy it was to remove the dash, don't get too excited. I managed to get mine out in less than 20 mins (I was rushing to get it the powder coaters before they were starting a run), but it took me 12 hours solid to get it back in.

My advice would be to obtain a small child with hands small enough to fit through the instrument openings to help you get it back in. All I had was the fact I managed to graze enough off my knuckles that my hands were then able to fit through themselves. Thankfully I was doing it outside on a UK winter's day so it was too cold to hurt.

Darren
D Lewis

I went through the wipers this last weekend.

Dash was already removed due to my wiring project on the car. The wiper assy them self's where easy to take off and put back on.

1) I tool the wipers them self's off
2)I took the nuts off all 3 shafts
3)I took the 2 bolts that hold the motor off.
4) took the motor out. The cable that is inside the tubing came with it.
The wiring had already been removed.
5) tried to remove the wiper tube assy but the defrost vents got in the way. SO I had to remove them. After I removed the vents the tub assy and the shafts came out easily.
6) Took the everything to my bench and started checking it out. With the cable pulled out of the tubing it was still hard to turn the shafts.
7) took all the bearing cups at the end of the shafts apart, cleaned them until the shafts moved freely.
8) cleaned the tubes out with some long pipe cleaners I got from wall mart craft center. The tub is in 4 sections. and was easy to clean with the pipe cleaners
9)took the motor apart and cleaned it.
10) lubed everything real well with white lithium grease.
11) put everything back together.
12) installed everything back in the car.

bsf Fowler

sorry for the miss spelling. #1 should have read

1) I took the wipers them self's off.
bsf Fowler

And??? Did they work any better? Sounds like the wheelboxes (that the wiper arms slide on to) were a significant factor.
Paul Hunt 2

I am in the middle of re-wiring the car so I can not tell right now. I am hoping they are better. They should be since they where so gummed up before and moved much better afterwards. I may jump some power into the motor this coming weekend just to satisfy my curiosity
bsf Fowler

Yep the wipers work a heck of a lot better.

I have wired the front half of the car now and Dan's diagram and instructions are very easy to follow. Now I am contemplating how I want to run the wires to the back of the car. Originally they where ran underneath. I am trying to find a good path to run them inside instead. I did see another MGB once with then run underneath but through some romex tubing to protect them. It did not look bad the way the guy did it.

Bob
bsf Fowler

Bob

Read Dan's Installation Guide for the 68-73 MGB Wiring Harness (available on his site). "MG ran the wires to the back of the car underneath the floorboards. It is recommended that you devise another routing method. The area under the floorboard is subject to a great deal of abuse - not a good thing to subject wiring to. To route the wires inside the car, you will need to make some holes in the body sheet metal."

I intend to run my harness to the rear inside next to the sill on the passenger side with a hole and grommet into the trunk area.

FWIW

Larry
69 C in restoration.
Larry Hallanger

Yea I was thinking the same thing. I guess I could hide it under the carpet in the corner or just run it down the side with some good cable clamps. Maybe even hide it under the carpet.

Bob
Bob Fowler

I must be losing my mind beside for the bad spelling I am repeating myself now.

Its been a log day.

Bob
Bob Fowler

I ran my rear cables inside the cab along the RH side of the trans. tunnel. The plastic plug/bung at the rear of the floor panel was replaced with a suitable grommit for the wires to exit.I used the original loom, so it is a stock installation from the exit point to the trunk/boot area.It makes an easier route for the loom to connect to the under dash wires via the console this way. My prime object was to get rid of the "rat's nest" wiring arrangement in the engine bay. BTW the carpet & seat do the loom in place without any cleats or clamps. Barrie E
Barrie Egerton

I ran my wires to the rear of the car last week. I also chose to run it along the transmission tunnel on the passenger side. It allows for the connections into the main harness, courtesy lights, switches etc. to be made neatly behind the radio console. I exited through the rear of the passenger compartment at the floor just to the right of the battery box which allows the harness to continue along the route of the original harness over the axle and into the trunk via the existing grommet at the trunk. I was able to reuse some of the original attachment points etc. over the axle, but care must be taken not to interfere with suspension movement etc. With some good loom the harness should be well protected. Need just two clips in the passenger compartment to hold the harness loom in place, the carpet will do rest.

Dave
David B

This thread was discussed between 09/01/2006 and 30/01/2006

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.