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  Alternator (24V)

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Alternator (24V)
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  24V Cosworth Scorpio

After a series of electrical silliness, such as instrument resets on startup, flickering battery light and a complete electrical blackout, I checked the battery with KwikFit, who discharge tested it. When the needle showed no change after 20 seconds it was clear that the battery was okay, which left the alternator as the prime suspect.

First of all, there is some confusion in the parts books for the Scorpio and it's as well to give you what information I have gleaned first so that you are better placed to get the right replacement, which is more than I managed. There are three types of alternator on the Scorpio range -
DOHC Bosch KC 90 amp
All V6 Magneti Marelli A1271 - 100 amp
Diesel Magneti Marelli A127 70 amp

For the 24V you are looking for a [looking from the front] LH mounted alternator with about 48mm between centres on the mounting holes. The unit I was given first looked correct, but had 60mm between the mounting holes and would not fit the solid bracket. Take a ruler with you when you go to the dealer and measure the distance between centres shown below, and that the rear mounting hole is on the right for the LH mounting.

The second alternator I was offered looked exactly right, but it was set for a RH mounting. I could have taken it, but unbolting the rear casing and moving it round 90 degrees would have meant invalidating the warranty, so I left the alternator behind and refitted the old one for now.

When you first look down the front of the engine behind the radiator and fans, you suspect that there won't be enough room to change the alternator - but in fact there is with care.

First - and this is most important - I disconnected the battery and tucked the positive lead away so that it can't creep back to the terminal. Be careful to use a short spanner and great care when removing the battery connection, the bonnet hinge is very close.
Then I needed to release the auxilliary drive belt. I found that I did not need to touch the AC compressor belt, I just released the left hand belt and pushed it out of the way. It's very easy to remove - if you know how. The left hand drive belt runs from the crank pulley up over the tensioner and down again to the alternator, then up over the power steering pump and straight to the water pump, then down to the crank pulley. The tensioner contains a large coil spring and requires some muscle, but space is restricted between the tensioner and the electric radiator fans. Ford suggests using a ring spanner from underneath, but I could not budge the tensioner at all, so I used a short 17mm socket on a small ratchet augmented with a piece of square steel tube to give extra leverage, turning clockwise, and the tensioner unlocked with a click and released plenty of slack to pull the belt from the alternator pulley. I then gently removed the clockwise pressure and allowed the tensioner to release fully.

If I were changing the belt I would need to remove the AC drive belt as well, but here I left it in place.

Reaching underneath without jacking the car up I could reach the engine undercover quite easily. There are four T30 torx head screws for the engine cover. They were removed and the cover pulled away. I then used the cross-member and a 3 tonne jack to lift the car and placed it on axle stands. It was not necessary to raise the wheels right off the ground to give plenty of room to slide under.

The alternator is secured with a through bolt and nut at the top and a single bolt underneath. In order to release the nut from the top bolt, I found it necessary to remove the o/s exhaust manifold heat shield - three 10mm bolts on the top and two underneath. The heatshield was drawn away and this provided just enough room for a small ratchet and 13mm socket for the nut, with a larger 13mm socket on the front to stop it turning. The bolt then free, it can be withdrawn as far as the radiator fan housing where it seems trapped. I left it there for a moment, then went underneath to remove the lower 13mm bolt. The two power connections are then removed using a very small ratchet at 10mm socket. I removed the large power wire from the top, which is a 10mm nut, and then removed the lower one from underneath. This is also 10mm, but is captive with the connector.

At this point the alternator is free to move, but the upper bolt is trapped. Looking up from underneath you can see that the radiator fan housing is secured with a slide and a single 10mm bolt in a slot. The right hand bolt is just beneath the top radiator hose. I loosened this off and then slid the electric fan housing upward to free the alternator bolt. The alternator can then be levered from the mounting and drawn round the power steering pressure hose to the ground.
On the right is a view of the alternator from underneath. On the top right corner is the radiator and the black pipe beneath the alternator is the power steering pressure pipe (this is the new one installed to stop the vibration at parking speeds. You can also see the Power Steering Pressure Switch which advises the EEC-V of impending load from the Power Steering. The bottom fixing bolt can be clearly seen. There is a glimpse of the Cosworth alloy sump beside it. There is just enough room between the pressure pipe and the radiator to fiddle the released alternator through.

Having looked at the new alternator it was then I discovered that it would never fit. The alternator bracket is rigid steel and the bolt holes must be in exactly the right place or the unit would never fit. Good thing I checked it before offering it up!

The bracket is black metal here behind the PS pipe - unless the holes on the alternator match exactly the alternator is useless.
I returned the new one to the motor factor and then we examined three more which should be right - no joy. One had the correct bolt centres, but was for a RH fitting!!

Nothing for it but to put the old one back until I could source the correct replacement.

I tapped the alternator bolt collar gently so as to loosen the alternator on the bracket in the engine, and then squeezed the alternator through the gap and offered it up to the bracket. Still working from underneath, I loosely installed the lower bolt to the bracket so that the alternator could not fall, but was roughly in the right place. Using the lower bolt as a fulcrum, I moved the alternator about from the top with the through bolt in the top hole so as to feel for the lining up. It is tricky here, because the radiator fan housing has to be pulled up at the same time to allow the slack for the bolt to line up. After a bit of struggling and bad language, the bolt slipped in and I put the nut and its washer on the other end. Both top and bottom bolts are torqued up to 25Nm. I then reinstalled the alternator connections, torque 24Nm.
The radiator fan housing needs to be retightened. Then I reinstalled the drive belt. Using the long bar on a small ratchet makes it very easy, despite the limited clearance, and I recommend this method. I checked that the belt was properly seated on all the pulleys. Done.
I lifted the car off the stands and lowered it. I replaced the exhaust heat shield, (bolts lightly tight) and then reconnected the battery and replaced the battery cover. I ran the car for five miles so that it could re-learn the engine data, and then checked for any error codes: none.

I entered the pin code for the radio - worked first time.

And the end result? Not altogether a waste of time. I have used the car for three journeys since and the electrical gremlins have gone - at least for now. There has been no flickering light, no instrument resets, nothing. Perhaps there was a loose connection? I will wait and see.

Incidentally - do not assume if the alternator is not charging that the battery light will warn you - it won't. The charge warning light will not illuminate at all if the alternator diodes or regulator circuit goes open-circuit. So check the lights in the instrument panel at start-up, if there's no battery light there's no power going into the battery!

Tools Required

T30 Torx bit
17mm short socket - extension bar
Short 1/4" drive ratchet, 10mm, 13mm sockets
Torque wrench
Trolley Jack, 2 axle stands

NB The charge warning light flickered the very next day, so I went to Ford, where I purchased the correct re-engineered alternator, which cost 125. It was installed in an hour, which shows how much difference rehearsal makes to any job!



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