Displaying items by tag: Electrical

A club member got in touch with me and raised the subject of fitting an electric fan onto a MK2. Some people think they are rather exotic devices however the majority of modern cars use them and particularly anything fitted with an east – west engine except the original Mini is almost guaranteed to be equipped with one. In addition have a look under the bonnet of your modern Commodore, Falcon and Magna and you will find an electric fan doing all of the cooling work.

It appears that one stumbling block for many people is the problem of fitting a sensor to turn the fan on when the engine is starting to overheat. There are several ways of handling this. One is to fit a sensor which plugs directly into the upper radiator hose. I consider this as rather crude and am more inclined to get a new thermostat outlet pipe and have a modern sensor fitted by machining an appropriate hole in the metal.

You might also investigate fitting a genuine Jaguar thermostatic fan switch as fitted to the E types and Series 1, 2&3 XJ among others. These were originally fitted in the cross flow radiator tank. Another access point is the original thermostat switch hole for the starting carbie which is generally redundant as most MK1/2 owners have modified their cars to use a dash mounted switch for the starting carbie function. You would have to do a bit of fettling to make a plate to carry a thermostatic switch

Another method is to fit a manual switch somewhere around the instrument panel. Anyone used to old Jaguars in hot weather will be monitoring the water temperature and it would be a simple thing to turn the fan on when it is starting to get hot. This is done in many competition saloon and sports cars which have had the mechanical fan blades removed. I am told that the only time the fan gets turned on is after the race and when returning slowly to the pits. Note that this switch needs to control a heavy current relay which will do the actual switching. Many modern electric radiator fans could be pulling upwards of about 50 amps while running and you would need an almighty big switch to handle that sort of load.

An electric radiator fan will consume about twice the output of the old Lucas generator. It may be worthwhile to consider fitting a modern alternator to carry the load particularly if you intend to drive the car frequently in traffic. The old Lucas generator has the further disadvantage of being “off line” while idling in traffic while the modern alternator will be on line and supplying power even when idling. I have alternators on two of my historic registered cars [a Mk1 and Mk2] and they are a boon in getting the battery charged quickly and giving better lights in traffic at night

Sometimes it is the simplest things that get you going (or stopped). One of my MK1s was doing odd things in that the generator and regulator seemed to be all over the place and sometimes not charging. One quiet afternoon I grabbed the digital multimeter and tools and attacked it.

The generator proved quite capable of putting out more than adequate volts and amps. This is a very simple test. Simply attach a piece of wire between the D [dynamo] and F [field] terminals on the generator and start the car. Don't over rev the engine, as 1500 to 2000 RPM should be adequate. Measure the voltage being generated at the generator D terminal. This will be typically in excess of 14 volts and possibly up to 16 or more volts. This is because you have bypassed the regulator. If the ammeter in the car shows a large output that also proves that the cutout is working. It pulls in when the generator volts are typically above 12 to 13.

All this was OK and I now suspected the regulator. I cleaned the regulator points but there was no change and I decided to replace it with a spare that I had. While undoing the terminals on the regulator I found that the screw for the wire running to the generator field was quite loose. Tightening this up was the answer and the generator now performed as Lucas and Jaguar advertised. Moral – look for the simple things first

A club member recently acquired a large British car of the better class [but it was not a Jaguar]. Driving it home some considerable distance, like from Victoria he had an electrical problem in that the Lucas generator stopped working. Parts were hard to get but he soldiered on by buying a spare battery and charger and only driving by day and charging batteries overnight.

The upshot was that there was nothing really wrong with the generator except the brushes were totally worn out and he found that by applying light pressure to the brush springs he could get the generator "on line".

A trip to see Kevin Baker the Lucas guru who lives at Maleny [ph 5494 4221] netted a set of brushes for one of the largest generators you will ever see in a car and the problem is fixed.

However I wonder how many of us are driving around with worn generator brushes. Unscrewing the clamp on the generator cover and simply looking at the top of the brush holder and spring easily inspect them. If the brush is well down in the holder its time to get in touch with Kevin.

The grey MK1 project progress hit a brick wall and stopped as I tried to get the windscreen wipers operational. I should have woken up that there was something pretty wrong when I saw the flexible drive cable from the wiper motor to the wiper arm gearboxes disconnected and I also had noted that an attempt at a roadworthy a couple of years ago resulted in a failure because of inoperative wipers and body rust. [The rust is all gone now.]

Removing the Lucas DR3 wiper motor revealed a lack of brushes and some pretty amateur soldering of new flying leads into the motor itself. By luck I had another wiper motor that had a seized armature bearing and I was able to use the field windings and brushes to get a basically serviceable motor running on the bench. But the wiring colour code seemed to be wrong and I could not for the life of me make out the switching system to get the two-speed operation. There are 6 wires running into the motor with the colours of red, green, blue, brown, white and yellow

I resorted to the internet to attempt to sort out the colour codes however there was nothing about internal wiring of DR3 wiper motors but the mention of the name " Lucas" certainly brought a number of jokes about the "Prince of Darkness".

Finally I pulled the top off the wiper motor in one of my other MK1s and established the correct colour codes. Whoever had installed the new leads had certainly got it wrong as only two colours of the 6 wires were correctly terminated I then connected the motor to the car system and all hell broke loose as the supply fuse got blown. What now? A crawl under the instrument panel revealed that in the past some one had installed a wire to run 12 volts from the fan switch to the wiper switch. That is not how it should be done and when the wipers were turned on the 12 volts was being taken straight to earth.

Obviously the system needed to be restored to original specifications and the wiper system is now working. I will do a diagram of this wiring in the future as the leads on these motors are now typically 40 years old the colour on the original wiring has completely faded out and anyone wanting to overhaul one is going to have difficulty without "the knowledge"

When I acquired the MK 2 the tachometer [as well as the oil pressure gauge] was not working. It became fairly obvious that one of the problems was that the tachometer [tacho] generator had a broken electrical connecting lug. This tacho generator uses the same principle as a pushbike generator to create electrical voltage by rotating a permanent magnet inside a coil. This electrical voltage is then fed to the tachometer instrument, which in reality is a voltmeter. The principle is that the faster the tacho generator goes the more electrical voltage is produced which produces a correspondingly higher reading that we see as revolutions per minute [RPM]

This same tacho generator is also used in the MK9, S type, earlier E types and Daimler 250. Enquiries for a replacement tacho generator part no C14996 resulted in prices in excess of $300. Hmm –it was time to put the thinking cap on and see if repairs could be affected.

An inspection of the terminal cap of the tacho generator, which uses push on spade connectors revealed that the lug had been broken off flush with the surface of the plastic cap. By using my trusty dremel tool I was able to excavate around this broken lug to a depth of about 4 to 5 MM or 3/16 inch. I was then able to cut the male section of a spade terminal down to a suitable size and solder it to the old lug. The whole thing was then finished off by using a dam of masking tape to allow a suitable build up of epoxy resin over the excavated area and the base of the new lug. This all resulted in a now sound lug projecting from the terminal cap.

I had checked the wiring from the generator to the tacho instrument and all measured OK with about 2.5K or 2500 ohms resistance, which indicated a correct circuit impedance existed through the instrument. I replaced the tacho generator [with a new O ring fitted] hooked up the tacho instrument, started the car and achieved nothing. The b.......y instrument was U.S. ! [unserviceable]. I was also able to check that the generator was working as Ben Stafford had lent me an old battered tacho with a partly broken needle etc. but still serviceable as an indicator and I hooked it up and it worked.

Muttering and cursing I removed the tacho instrument [and a couple of squre inches of skin as well]. I cleaned off the workbench which is a miracle happening in it’s own right and laid out some clean cloth to allow me to dismantle the tacho. It does come apart very simply as the faceplate only needs to be twisted to align the spaces on the faceplate with the lugs on the case. The faceplate can then be lifted off. The tacho instrument itself is only secured in the case with two screws and the clock at the bottom can be left attached to the case.

Applying gentle pressure to the needle revealed that it would move but was rather bound up on the “jewels” or pivots. In my time as a radio technician and later on in aircraft engineering I had been exposed to and qualified to do instrument repairs. One facet of instruments that few people ever consider is that they do need lubrication. More particularly so as they get older and the original lubricants dry out. With an artists brush I applied some penetrating oil to each of the needle pivots and allowed it to take effect. After about an hour the needle was quite free and I applied some sewing machine oil to each pivot. The needle was now quite free and I reassembled the instrument. I made a temporary connection between the tacho generator and instrument, started the engine and wonders to behold it all worked.

Tearing off the usual square inch of skin in the process I refitted the tacho and reconnected the wiring. A quick check ensured that all was functioning and the beer fridge in the shed was raided to celebrate.

I have been intrigued by an on going problem in the 1960s model Jaguars such as MK 2, S type, E type, 420 etc. The main area of concern is the oil pressure gauge. This is an electric device that was apparently Smiths first foray into the domain of electrical transmitted oil pressure. Apparently the Jag Enthusiasts Club in England has also been following up on this problem.

To say that the Smiths electric oil pressure gauge is an accurate instrument would be taking the truth very lightly. It is one of the most Heath Robinson devices I have ever encountered in any instrumentation. Normally an instrument transmitter contains a device a bit like the variable resistor used in volume controls in a radio. These are generically referred to as "potentiometers". As the temperature or pressure changes the variable resistor feeds more or less voltage to the gauge in your dash panel to make the indication. Simple enough?

However Mr. Smith put a whole new twist on the scene by using a system in his oil pressure transmitter that works as follows. The flexible diaphragm in the transmitter has an electrical contact on the diaphragm. When oil pressure expands the diaphragm this contact connects to another contact on the end of a bi-metallic strip. This makes a circuit through a heating wire wound around the strip which heats up until the bi-metallic strip bends and breaks contact with points on the diaphragm.

The bi-metallic strip then starts to cool down and straightens out until contact is made again and the process repeats. The more oil pressure there is the longer it takes for the strip to heat up and therefore the more electric current runs through the system. This current is measured and shown on your oil pressure gauge as pounds per square inch!

The bi-metallic strip system is well known and is used in the majority of "flasher" units in directional indicators in motorcars. However they do not last forever and eventually they fail due typically the points burning out. It is an electro/mechanical device and as such will never be a stable source of information for a gauge system.

Why I am making this point is that an old oil pressure transmitter can give quite erroneous readings. One club member was really quite concerned with his oil pressure in an XK series motor in a MK2, which only ever got to about 40 PSI cold and was flat out making 20 PSI when hot. The engine was generally in good order and was not rattling or giving any typical signs of distress associated with clapped out Jag engines. On my suggestion he obtained a direct reading after market gauge and coupled it up in place of the electric system and was delighted to find that all of the above pressures were just about doubled.

I have also run across this problem and have had widely divergent readings from different transmitters. In fact I trust the older Bowden Tube direct reading oil pressure gauge used in early Jags like the MK5, 7, 8 and MK 1 any day against one of these later electrical devices.

The good news is that a company by the name of CAREBONT in England have purchased the rights and tooling for early Smiths gauges and have redesigned the oil pressure gauge for these 1960s Jags. This kit apparently consists of a completely new transmitter and gauge using modern techniques but looks just like the original. It is not cheap at around 70 pounds or about A$200 [Australian] dollars but the current price for a new oil gauge transmitter to fit the old system is A$130 so it would be worthwhile going the extra dollars for something new, reliable and accurate.

If you are a qualified electrician or a member of an allied trade/professional then don’t bother any further with this article. However if you are a non technical person who is occasionally baffled by electrical problems and their associated terms then the following may help you understand the basics of car electrics.

I also pay my respects to the anonymous author who first wrote the famous ditty on “Joseph Lucas - Prince of darkness - or why the poms drink warm beer” where to my knowledge the concept of electrical energy as smoke was first published..

As a 15 year old apprentice radio/radar technician I still remember how hard it was to come to grips with the concept of electrical energy. You can see it in lightning and sparks; feel it in an electrical shock; smell it in ozone; actually taste it by putting a 1.5 volt battery on your tongue [it tastes salty]; hear it in electrical spatter across insulators, bangs in thunderstorms and the zap of an electrical spark. But in the end you are still left wondering what it is, as all of the foregoing are actually secondary characteristics of electrical energy.

I just about have a heart attack when I see people incorrectly connecting or disconnecting batteries in vehicles [or aeroplanes]. Do yourself a favour and read this carefully. I will refer to the batteries “live” side being the terminal above earth and the “earth” side as being the terminal, which connects to earth. This is because the original polarity of a lot of early Jags was positive earth and later models were negative earth. In addition a lot of early models have been converted to negative earth. The use of the terms positive and negative is inappropriate in these circumstances.

In relatively quick succession two family cars decided to have flat batteries namely the MK 1 and the Datsun 120Y. There was no basic reason for this problem as both vehicles had relatively new batteries. Both were recharged and the MK 1 had the battery lead removed from the battery terminal.

About two weeks later I went to start the Datsun but only got a very weak starter and no inclination to fire. I promptly hit it with jumper leads and it started and run normally. However this loss of electrical power was a problem that needed solving. I connected the multimeter on amps range between the battery and the lead and noted a very slight drain of under 1/10 of an amp. In fact it was about 80 Ma. Now that is not a high discharge as 80 Ma equals 80 thousandths of an AMP.

By sheer luck I ran across a chap named Kev Baker at a swap meet last year. Kev runs a business called K B Classic parts at 2 Margaret St. Witta via Maleny and describes himself as an "Automotive Electrical Parts Consultant and Supplier."

I had been chasing a couple of those fine thread nuts for my Lucas spotlights which are standard on the MK 1. Every avenue seemed to be exhausted when at a swap meet Kev was pointed out to me by a Victorian electrical parts stall holder as the "Giru of Lucas parts in Australia". I approached him and described my problem. Within a couple of weeks I had the brand new nuts at $ 3 each. Another club member had been chasing a new distributor cam for a MK1 with no success. I contacted Kev and he immediately came back with a confirmation of availability and price.

While I urge support for the suppliers who advertise in this magazine you might consider using Kev Baker for those really hard to find electrical parts. He specialises in mail order and is available on phone 0754 944 221 and fax 0754 944 114