Writing about how to repair or improve MGs, and having developed my own MGs to a good spec/condition doesn’t exclude me from having failings of my own from time to time. For example, my MGB V8 roadster - whilst residing under its soft winter cover in the garage - displayed a problem with heater fan non-operation on one of the few dry day opportunities to take it out in winter. This didn’t help clear a misted inside of the screen.
The issue was intermittent operation of the first speed and almost no response by the second speed. Whilst my car may be a 1968 model, I converted it many decades ago to V8 which required a steering change. Whilst I kept the original dash with modified solid column for a decade after the initial conversion in the mid 1990’s, I decided that I would prefer to have the added safety of the later collapsible steering column and direct acting dual circuit braking, even though this was a considerable amount of work.
I also added face level vents which added a dash change to the ‘to do’ list which would also cater for the wider column. Using the 1977 on. five dial dash wasn’t my initial plan, but being unexpectedly presented with a removed dash complete with all gauges and switches at a car boot sale for £40 steered me; and also meant my change to a new wiring loom could be matched to cater for all the different wiring plugs for the switches.
I don’t dislike the later dash, and simply using new magnolia faced and correctly calibrated clocks from MGOC Spares, plus an RV8 steering wheel presents a very acceptable and matching alternative. Over the twenty five or so years since converting, I have had no issues with the change and have only had the usual need to renew a hazard light switch and a flasher unit a couple of times when they start their (not uncommon) go slow, or no flash.
Seeing as this dash was created in the era when BL went bust meant that many aspects of cars and their parts in the years before and after going bust (and being bailed out by the UK Government) have been shown to be a little flaky. The commonly used later switches found on a myriad of BL cars including the 1977 on MGB dash look a little flimsy, but the reality is that they have in most cases provided very reasonable service; and twenty five years service in my car for second hand parts has confirmed that. However, nothing lasts forever and the errant operation of my heater fan was soon confirmed by the switch, as being able to push on the switch and generate varying fan operation, along with shorting between the wiring plug terminals provided both fan speeds. Note that the heater assembly is a post 1977 one, so it has the internal resistor and two speed fan operation.
I did take my switch to pieces and this is simple as you just need a small flat blade screwdriver to gently ease the switch out of the dash. Or if you're worried about scratching the fascia then pull off one of the face level vents from above, and in seconds your fingers are behind to push the switch out. The downside is that when putting the face level vent back in, it is a little awkward getting one hand behind the dash to position the concertina air pipe to engage with the plastic vent (but it is only a slight fiddle).
Splitting the switch is achieved by using that small, flat blade screwdriver down between the pivoting part of the switch and the outer casing and gently levering it so the moulded pin comes out of its socket and allows the pivoting part to partially come out. Repeat on the other side and have a controlling finger on that pivoting part as there is an internal spring wanting to do the Swiss watch dropped on the floor, escaping parts show. Controlled easing out will see the spring pressure ease and note the positions of ALL the parts, so when you come to reassemble you get the right order. Also pay close attention to the orientation of the pivoting part in respect of the switch body. Note the body has three connector terminal pins on the back, biased to one end of the switch.
The reason for my erratic fan operation can be seen in the state of the pivoting connector plate and why it was not transferring power well. Usually, over the many years of service carrying the full electrical load, the connections get a little dirty and this creates resistance, and resistance creates heat, and heat softens the plastic very slightly. Over many heating cycles the plastic shrinks and the contacts actually separate; similar problems can affect the dip/main contacts in indicator switches.
The removed fan switch internal parts showing how over years dirt and corrosion builds up to degrade power flow.
This was easy to clean up to a bright copper finish and a similar cleaning was applied to the internal ends of the switch body's pins before the switch went back together, but I had put the parts back into the switch body upside down!! Anyway, split it again, turn the inner parts the correct way and refit. It was only a partial success, with a full working slow speed and still erratic fast speed; no doubt due to the shrinkage mentioned earlier. So I split it apart again and check the contacts, reassemble and it was worse, and a couple of other attempts couldn’t better an iffy fast speed. Onto what I expected I should have done in the first place, and order a new switch from MGOC Spares which arrived the following day and within seconds, it was in and the fan was fully working again.
Cleaning up the copper parts to present the least resistance to power flow, unfortunately didn’t fully work with this switch.
New switch (far right) a two minute fit into the dash for normal service to be restored.
I did consider changing to the noticeably more effective MGOC Spares 2 speed heater fan conversion, but the work changing a switch compared to fitting the heater conversion was a job for another day, although it would be nice to have a heater that lived up to its name!
2 Speed Heater Motor & Large Impellor Kit & Heater Matrix
Looking for more MGB parts? View our full range HERE.
Please Note: The information provided in this blog is intended as a general guide only. While we aim to ensure accuracy, classic vehicles can vary, and procedures may differ depending on model and condition. Always consult your vehicle’s official workshop manual before carrying out any work. If in doubt, seek the services of a qualified professional.
© 2025 MGOC Spares Ltd. All rights reserved.
This blog and its contents are the intellectual property of MGOC Spares Ltd and may not be copied, reproduced, or republished without prior written permission.
For author enquiries, corrections, or reproduction requests, please contact: blog@mgocspares.co.uk
Meet Roger Parker – our MG “Tech Guru” with a lifetime of passion for all things MG!
From his early experiences with MGs, to a career as a traffic officer developing ANPR systems, advising MG Rover and then as a technical advisor & writer at the MG Owners’ Club – Roger has worked on hundreds of MGs. Now, in “retirement,” he shares his unrivalled knowledge with us at MGOC Spares.
His blogs (exclusive & free!) are packed with expertise you won’t find anywhere else.
View more here
Who are MGOC Spares?
At MGOC Spares, we provide dedicated parts and accessories for classic MG vehicles, including the MGB, Midget, MGC and many more.
With thousands of products in stock, we are your one-stop shop for all your classic car needs. Our wealth of expertise means that you can trust us to find the right part for your classic MG vehicle – whatever it may be.
Need support finding the right parts for your MG?