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MG MGB Technical - Blaaat

I thought I had fixed this by getting a new starter that's being sold as lighter and more efficient.

Previously and now again today it happened:

Only when its hot out and I go to start the car I would get "Blaaat" (like a dead battery) when trying to engage the starter. Battery is pretty new, cable is new from the battery to the solenoid. Ignition switch is pretty new.

I finally chaulked it up to a funky soleniod so I was suprised when it happened today. Connections are all tight.

There's not a lot in the starter circuit. From a previous post I went on the assumption its the starter. Now I'm not sure what is causing it.

Check the engine ground connection. Cheers - Dave
DW DuBois

I know this one sounds basic, but check the battery terminals and cable terminals, It really sounds like lack of power to the system. I have a similar issue with my tractor. Everything seems tight, but it just clicks, redo the terminal connections and it fires up.
Bruce Cunha

If everything checks out electrically,it could be a bad "Bendix" drive not engaging or just a partial engagement. that would mean a bum starter motor. Hope you still have the receipt and box.


79 MGB
gary hansen

See attached for how to check for bad connections and cables
Mike Ellsmore

If lights dim right down when it happens it's probably battery or battery or solenoid connections. If the light stay bright, just flickering slightly if at all, it's probably the engine or gearbox earth strap.

You can check the battery with a meter across the terminals when you crank. Cranking normally on a good battery should show about 10v - take the readings on twin 6v batteries separately and add them together as the link cable could be faulty.

Then take a reading between the solenoid stud and a good body earth - if this is low it's probably battery connections including the battery earth cable or the battery to solenoid cable.

Then between the solenoid stud and an engine earth - if this is low it's probably the engine or gearbox earth strap.

If all those are good then you need to measure the voltage on the operate terminal of the solenoid - usually white/red, and the operate terminal on the solenoid. Bad connections in either of these two circuits especially the latter will cause the solenoid to chatter.

Thanks! I'll check everything today.

Paul - thanks for the precise detailed instructions. I'm getting a battery monitor that plugs into the cigarette lighter coming soon. I was curious to see what it reads. If I can duplicate it still after all the checks. I have a good timing light that reads everything.

When I put the engine together in the bay I used stainless everywhere including the earth strap. Some say stainless isn't a good electrical connector but many sites claim the opposite. Just an FYI as I go through the process.

Odd it only happens when it's really hot out and in direct sun.

btw, good link Mike!

Quick followup: Still checking. I don't think this has anything to do with it because the tranny gets ground from the engine - but - I don't have a ground on chassis to trans.

Is that any big deal?

There's a new one on the engine mount to chassis.

Went through everything without overt issues.

1. Checked battery terminals. Have those circular pads under each terminal and they seem to work. Zero corrosion or any sign of crystallization. Cleaned the terminals and connectors anyway both with baking soda/water, steel wool and blew off with air. Put some dialectic grease on the posts before putting on the terminal clamps.

2. Measured across and then at the clamps. Exactly the same.

3. Measured for continuity on ground/earth (-) and chassis. Instant confirmation.

4. Measured at the solenoid post to ground. Not even .01VDC loss. Exactly the same as the battery. 12.10VDC resting.

5. Checked the engine ground strap. Tight and secure. Measured ground from the block to chassis no issue.

All I could really see which I've been meaning to solder and fix is the lead to the top of the solenoid to engage with the key. I'm not sure this is it because if that wire is in the wrong position nothing happens at all. The seller couldn't recall on the new starter where that wire went and first, it was wrong - nothing. Then right - fired normally.

It has that barrel style crimp connector between the orig. wire and the extension.

Will drive it until it repeats or magically dissappears. Hopefully, its like that tractor. :)


Max, did you check the voltages at load, when you are trying to start the car? You need four hands or alligator clips on your volt meter leads. Mike
Mike Ellsmore


Could you expand on--
"Blaaat" (like a dead battery)
Is it a click or slow turnover or nothing or a series of clicking noises-------------?
William Revit

William - all of that. First like a dead battery. Then the others.

Mike - I was hoping for that meter that's coming in a week to watch it when I crank. I might be able to wire up the timing light and watch it through the windscreen.

But when I wrote the voltage, I paused. Its on a trickle charger right now (2A). A resting battery should be ~12.5 -- 12.7

Mine showed 12.10 Its been unusually hot here 105 (40.5C) and I wonder if its running any havoc with the battery. Its a Westco from Moss and not cheap. The selling point was it would last years and years and had a newer battery technology (AGM). Already had one go which Moss replaced.

I have the battery liners so it has to be a group 26/26R Local place said they carry Deka which I never heard of before. Used Diehard in the past, Bosch, Pep Boys....Can't fit an Optima which I guess is the best. Too much though right now.

Maybe the whole thing is something I didn't account for which is a battery going south. I'll check the cranking voltage in the morning after the charge.

Appreciate all the help. The investigating just might have turned up the real fault we weren't expecting...

Attached is a readout from my recording volt meter showing the voltage drop at the battery terminals when trying to start my MGA (9) times without any choke on a cold day, it started on the ninth time. My battery may not be in the best condition but it does show the voltage drop when under load as compared to no load.

Mike Ellsmore

Thanks Mike. No doubt!

I know everything in electronics changes when it under load so I sure you're right in the battery. I'll try in the morning with my 5568 and see if it holds the voltage number when cranking.

You can only get a sensible voltage reading when the circuit under test is carrying it's expected load, i.e. cranking in this case. If it's not carrying any current then you won't get any volt-drop, and it's the volt-drop you are looking for.

Continuity i.e. ohms is also not a good test of circuit connections. If there IS a weak connection anywhere there is every reason to expect it will be varying when it is carrying the expected current, which is another reason why except in very few circumstances would you use anything but voltage, both across the battery or a component, but also along a circuit between battery and component.

I've never heard of a stainless-steel earth strap (except for corrosive environments like under-sea), it should be tinned braided copper for its good conductivity.

The gearbox and engine should have no problem getting an earth from one to the other given the number of places there is a tight metal-to-metal connection, that's why only one or the other was ever earthed from the factory, never both. If you can't measure zero ohms between gearbox and body, then either one or both of your meter connections is bad, or the engine isn't earthed. However I suspect the former, as if the engine or gearbox earth strap has failed they will usually find a path to earth via a number of other routes such as the accelerator, choke and heater cables, and where fitted the temp gauge capillary tube. These will usually be enough to turn over the engine, albeit very slowly but without causing the solenoid to chatter, but getting hot and smoking in the process.

You need to measure the voltage between the solenoid operate terminal and the starter body when cranking, and work from there.

I am a newby to this site and my suggestion my not be relevant, but I know if the ignition timing is to far advanced it hits back when trying to start, that is the motor against the starter. Is this a possibility Max
R J Pemberton

Couple of questions -

Is this a geared reduction starter motor that you have fitted?

What happens if you flick the ignition switch quickly from "on" to "start" then back to "on" then "start" normally? So like a double start operation.
Chris at Octarine Services

Chris - this is like a gear reduction starter. I'm sure you know the one. Not that large but some kind of newer tech. Classic look. I never tried that and I will. Thinking back I did that however, I can't say how quickly. Here's their descrip "This is a 100% BRAND NEW Heavy Duty Planetary gear reduction starter for a MGB 1968 to 1980."

I'm now focused on the battery. I guess its time is up in battery years. I take extra care and just last month had the charger on it for a week which this battery charger means in that time it will recondition the battery completely. At least that's what the company and the sales person said.

After the night of charging it registered 12.6VDC. Crank was 10VDC. Last night I interupted charge and crank was 9.95 VDC.

Drove it around and tested after sitting for several hours. Still registers 12.56VDC but it fired immediatly so I couldn't get a good read on cranking. I'll have to pull the coil wire. Otherwise fired normally. But its not in the 90-106 like its been. It was only in the 80's (26.7C)

All this was done via the cigarette lighter which is where I charge it. I pulled bonnette connector and tested there with a DMM. I'll pick up a remote starter switch which will allow me to test at solenoid.

Well, unless the description is deliberately lying it is a gear reduction. Could be the pinion is incorrect for your flywheel, but if the old and new give the same symptom and they are two completely different types that is unlikely, and if the old one worked properly for years it's not possible. When you wrote "I thought I had fixed this by getting a new starter that's being sold as lighter and more efficient." I assumed you had replaced an original type, but maybe that is a wrong assumption.

It does depend on just what 'Blaaat' means. I've heard some starters making a shrieking noise which sounds like the pinion is skidding across the flywheel teeth, but with two or three repeat attempts it will engage and then start normally, which is maybe what Chris is referring to with the quick 'flick'. What is the condition of the pinion teeth on the old starter? Did you check the flywheel teeth before fitting the new starter?

The voltage when it cranked OK indicates the battery is fine, but you need to measure the battery voltage when the problem is evident.

A conditioning charger WILL recover a battery that has been languishing in a fully or partially discharged condition, but there are other faults that can develop. However I think it's fair to say that a battery going intermittent is fairly unusual. The temperature thing does indicate to me that it is a poor connection somewhere - if it is the solenoid that is chattering rather than the pinion skidding on the flywheel, which nevertheless could be in or at the battery or anywhere else in the circuit.

No Paul, nothing to do with bad pinion engagement.

I have found in the past that a quick flick of the switch will "spot weld" a bad connection and then the second switch on works normally because of the "weld".

Personally, I would forget the meters - clear access to all the connections and jack up the front so you can get at the starter. Then pull the LT wires off the coil and run the starter for a while - hopefully when misbehaving.

Starting at the battery earth, work your way along the cables to the starter and engine earth, feeling for any hot spots at connections. The bad connection will be noticeably hot.

Since you seem to have been through most things, my long distance suspect is the bolt that holds the battery earth strap to the body.
Chris at Octarine Services

Voltmeter will tell you where bad connections are by working along the connections, as well as the battery state, and how warm is too warm? I suppose it depends on one's background - mine is electrical/electronic.

Although I said to check the battery when the problem occurs, that is in case of an intermittent battery, which I doubt. Even when the problem is not occurring, a voltmeter will show bad connections, as they are unlikely to completely 'repair' themselves. From 12v battery post to solenoid stud, and from earth post to starter body, the total volt-drops in both circuits should not exceed 0.5v (Lucas Fault Diagnosis Manual). I have seen as much as 3v, but it still cranked albeit slowly. There are also ways of testing the voltages at the solenoid without getting underneath, described here

Not having electronic fingers I can't tell you how warm - but you will know as soon as you find it!

You're still going to have to get under to fix it if it is the main cable or starter connections.

Because the starter draws such a large current there will still be heating at a bad connection even if the voltage drop is as low as 0.5V.
Chris at Octarine Services

Thanks! I'll sort through everything meticulously. No concerns getting under the car. I need to replace all the OD O-rings anyway.

I'll run it several times with the coil disconnected and feel for heat. Actually I have an infared heat gun which may allow me to check faster.

Years ago I recall the issue of the battery earth and grinded the area down until it was clean then attached the cable. I'll check again and redo as needed.

Had a good think about this, and here's my new theory
We had trouble similar to this years ago on Ford Falcons which had their starter jammed up under the exh. manifold--The problem ended up being heat soak causing the starter solenoid to drag and the power source to the exciter wire on the solenoid wasn't enough to drag it in--A relay to the solenoid fixed the problem
I'm thinking that maybe after a hot run and then parking you might be getting heat soak enough to bind the solenoid which combined with MG wiring could warrant fitting a relay
The way to tell if this is the fault is to listen when you go to start it --If it just goes click or click click click it's a possibility---but if it actually gets into gear and only turns over slow it's not the solenoid but either battery or it's connections
Could be sticky starter motor brushes but if it's new and doing the same as before, I doubt that it will be those
Your volt meter reading when it happens will be a usefull guide- make sure you know what the reading is in normal conditions, cranking so there is something to compare with
Also, when this happens how do you start it ,do you have to wait and it comes good or do you try again and it's ok

William Revit

Heat does affect the V8 starter as one of the down-pipes runs right past it, and chattering was the first symptom. Initially doing voltage tests showed that the solenoid operate weren't as good as they could be, and improving those 'fixed' it - for a while anyway. Eventually I had to replace it. However the 4-cylinder exhaust is on the other side, and as this is happening on an old and a new starter, it's unlikely.

Great minds! and I appreciate it. I'm not jumping to blame the new starter like the old. No flywheel skidding. I wondered this on the old one. Old did click, click or nothing.

When the new one did it the sound also was met with blaat ie a weak battery. After charging I haven't yet ecountered it however, I'm going connection to connection.

The car comes with a starter relay stock. I replaced it once against the suggestion of a mechanic. He was right. It had no effect.

Here's the battery negative wire. Inspecting it I saw wear. Measuring it resistance was only .7 ohms. Really nothing. Anyway, I replaced it. Replacement is zero ohm resistance.


close up


Willy - forgot to answer you question. On the old starter I would have to get a push start on hot days. It was intermitten which made it hard to diagnose.

The day it happened 2x on the new one it was as stated above. Yes, I would try again, or let it rest and try again. Luckily it caught.

I believe the wiring harness at 45 years old is begging for a redo I'm just to lazy to redo the entire harness. While I regularly clean the bullet connectors I know the wire itself has got to have resistance due to corrosion over the years.

0.7 ohms is a huge amount in a starter cable. It will limit the current that can be drawn to less than 20 amps, compared to the 150 or so the starter needs.

Resistance readings are no good when poor connections might be involved, as by their very nature they are variable. They could get much worse when carrying a current, or much less. It's why you can really only look for problems like that when the circuit is fully connected and being operated in the normal manner.

As the Lucas Fault Diagnosis Service Manual states:

"The majority of procedures involve circuit testing and the principle used will be that of checking for 'voltage drop' where a voltmeter is connected in parallel with the particular circuit to be tested.

"As voltage drop exists only when current is flowing and varies according to the amount of current it is essential that the circuit is tested 'under load', i.e. whilst passing its normal current. In certain cases this current will be measured using a test ammeter."

Testing of the starting circuit by measuring the volt-drops in the 12v and earth circuits, including testing the battery itself, is covered in detail in the manual in the section on Starters on page 10. There are plenty of copies of that manual scattered around the internet, which can be downloaded, just Google it. Look for the entries that show it as a PDF file, such as this one

Unless the wire is seriously corroded and has thinned, it's connections between wire and connector, and between connectors, that will be causing bad connections. I did have a headlight wire corrode through some years ago, but the three wires had no outer sheath, the insulation had been damaged, and it was in the wheel arch hence exposed to all the weather. In the past I've examined wires that had spent many years running across the car immediately behind the radiator grille i.e. also exposed to the weather, and although the effects of that weather had run under the insulation from bullets, it was no more than tarnishing. Given a good original connection to its bullet, the wire itself wouldn't cause a problem.


So you replaced it - has that solved the problem?
Chris at Octarine Services

Paul - Even though this was just the ground/earth strap? Not the starter positive lead? I'll go through everything meticulously.

Chris - I'm reconditioning the battery. Luckily I work at home and have been able to use my wife's car while I sort it all out. I have to start using the B again tomorrow. Its been such an annoyance I want to check everything possible this time and correct if needed.

Ugh. This didn't make the time limit for edit:

In electronics I measure old wire and its not carrying proper current. Even covered. Since electricity runs around a wire and not through it small amounts of tarnish corrosion create resistance/impedance.


I'm not Paul, but you asked, "Paul - Even though this was just the ground/earth strap? Not the starter positive lead?"

Yes, of course. The ground is half of the equation required to operate the starter. If you disconnected the ground, nothing electrical in the whole car would work.

C R Huff

Hi Charley - of course. Makes perfect sense. I mis-spoke. Thanks.

More input.

Bought a remote starter. By cranking the starter at the starter and measuring load it quickly bounces between 9.44-11VDC all within the same single cranking. I did this several times. Some times it dips to 10VDC. Sometimes 11VDC. It ranges greatly.

Resting drops to 12.10VDC, however after a minute it comes back up to around 12.56/12.6VDC

Renewed the push on connector at the starter solenoid ignition switch relay. Made sure it was a tight fit.

Will take the car out tomorrow for a lot of stop and go. We'll see results. Still working through the PDF Paul linked to. Eventually I want to get rid of that crimp on barrel connector as pictured above by soldering the lead.


“Since electricity runs around a wire and not through it small amounts of tarnish corrosion create resistance/impedance.”

This is only true for high frequency AC and is known as skin effect, in DC and low frequency AC the current flows through the middle of the cable. As Paul says, unless the cable is thinned by corrosion or damage the issue will be at a joint between the cable and the connector or between connectors.

An intermittent problem is the worst to find, if it was smoking you’d find it straight away. You need to be methodical, this can involve either using the various suggestions and working your way through the circuit or you can go through and clean/replace every joint. The first is preferable as that way you’ll hopefully locate the problem and solve it.

As Chris has said, if the issue is a joint in a high current circuit it will get noticeably warmer quite quickly. If you can get hold of a thermal image camera it might help, they’re becoming more common, I’ve just got a new multimeter with one built in, I use it for finding hot components on PCB’s

R.A Davis

An infra red thermometer might do the same job as a thermal imageing device. Maybe systematically spraying the joints with a lubricant might show a heated joint with a little vapour!
Allan Reeling

Lol - why make stuff complicated when a mark one thumb will do the job??
Chris at Octarine Services


I agree KIS is always the best option but if you’re looking for something that’s warmer than it should be these devices are great. For the first week, I was pointing it at all sorts of things.

R.A Davis

All good. Reason I mentioned the IR gun is for speed more than accuracy of digit. Plus I have one. :)

Agreed completely on intermittent which is why I want to go through everything I can and renew anything slightly suspicious. Then I can eliminate those if it hits again.

Good point on skin effect not being accurate with DC.

Slightly off topic: I encourage anyone reading this in the future to focus on all grounds. By cleaning and newing grounds I've solved everything from bulb brightness to, as seen here, battery strength.

You mentioned back a few posts that you had reconditioned the battery
Was it faulty-what was wrong with it--
has it been load tested
and what have you done to recondition it
and my last anoying question
Have you measured to check the out put of the alternator
William Revit

Hi Willy - I did recondition it again and drove it a lot yesterday.

According to the cig voltage meter (checked against a proper meter which showed it read .2VDC low). I don't trust it for cranking. I'll use a meter in the bay and crank it with a remote starter and see how low it goes.

So according to cig voltage meter the alternator would run 13.3-13.8VDC.

I went through my receipts and that battery isn't as recent as I thought. Its over 8 years old. A poster warned batteries have gone up in price and they're right. I'd like to get another AGM battery which is quite pricey.

For now its holding and cranking. Its going to have to be replaced eventually.

Want to be sure the alternator is charging proper. As mentioned above its in the 13VDC range.

I read this: "with the engine above 2000 RPM and no accessories the output voltage should be between about 14.3v and 14.7v"

Should I have the alternator tested?

14 1/2 is getting up there a bit
Most modern cars would probably be up there to feed all the electronics but your MG would be a bit lower I reckon
Basically--if it holds above 13v under most conditions above idle it's charging and ok

still a bit interested to know what your take is on reconditioning the battery
Do you mean recharging or is there something else being done-------
William Revit


Thanks. I did mean recondition. The charger I have has multiple battery types and amperages. Its called: BatteryMINDer 12 Volt 2/4/8 Amp Wet/Gel/AGM Battery Charger

Its supposed to recondition a battery if left on for a week at 2A. You can read about its method on their site. I think my model has been superceded. Best I can tell is once it charges the battery it goes into a cycling mode bouncing the voltages up and down constantly which (guessing) forces the battery to work in a different state. Claims to desulfer batteries but mine is a AGM which I don't know if that applies.

Anyway, the most standing voltage the battery had once charged and used right away was 12.10VDC. After almost a week it now has resting voltage of 12.6VDC.

Some of the claims are lofty. Its seems to work for me.


If it works, that's all that matters
William Revit


Went through everything explained here and linked. Could not find a fault. Then went to an auto electrical shop and had them test the alternator and battery. Alternator put out 3.9A and they said that was fine. They checked and its a 55A alternator and suspected it was a Valeo. Then I asked them to check the battery. The machine said it was ok. I watched the load test and while it did at one point go down below 10VDC it mostly stayed above that.

When I told them the age of the battery they thought I was goofing. But the receipt shows it was purchased late 2006. After hard blinking they said its going any time now and should have gone long ago.

So maybe that battery 'pulse' reconditioning does work. ;)

Thanks to everyone for all the good advice. I'm sure the battery neg lead had its hand in the ussues. While checking I did clean and renew connections.

This thread was discussed between 04/08/2017 and 14/08/2017

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