MGF SPEEDO NOT WORKING

[kevinarbury1]

Hi All,

I have an MGF 1998 which I bought back in Feb this year, great little car and lots of fun to drive!

I have had various small issues from overheating to lights not working properly, all of which the problems were solved.

The next issue to plague my driving pleasure is the speedo no longer works which in turn deactivates the power steering so you have to stop and pull the 70 amp fuse under the bonnet every now and again, then its all good for a while! I have had everything changed from the speedo drive gear, all 3 sections of the speedo cable, all the way through to replacing the instrument cluster in the dash...still doesn't work. 2 different garages have diagnosed it as totally different problems, neither seem true especially as I have just fitted the replacement cluster and conducted an experiment myself.

I disconnected the speedo cable from the rear of the replacement cluster and took a short drive with the end of the cable to hand...the square drive inside the cable does not rotate as it should do! as everything has been replaced it must be a problem inside the gearbox itself but what would this be??? how much to fix it??? where???

any help much appreciated!

cheers,
Kev

[kevinarbury1]

I have also read online of an earthing problem but my speedo cable is mechanical not electronic...would this be a potential problem?

[talkingcars]

Hi and welcome to the forum

I have the same issuie on one of my cars but I'm yet to check it out.

You should be able to get the cable to move if you jack the rear of the car up, put her in gear (5th would be best) and rotate a wheel, with both wheels raised you should overcome the diff. If I'm correct the cable should turn.

I would start with the bottom section and work up.

James

[kevinarbury1]

Hi James,

but the whole cable, all 3 sections have been replaced, are they fragile?

regards,
Kev

[talkingcars]

The mk1 speedo is purely mechanical.

[talkingcars]

You could start by checking the output on the speedo drive on the gearbox.

Did you use new or used speedo cable?

[kevinarbury1]

the engine runs so sweet and the gearbox sounds great so i don't understand it?

[kevinarbury1]

brand new, the garage charged me 250 to do it

[kevinarbury1]

how do i check the output?

[kevinarbury1]

thankyou for all your help already by the way

[Plezier]

Well you need to undo one bolt and lift the cable up out of the gear box and see if the inner is intact.

[talkingcars]

You should be able to see the drive on top of the box turning.

I guess one can turn the gearbox end of the cable and see if the speedo end turns.

[kevinarbury1]

can I access this from the top or do I need to arrange some ramps etc?

many thanks guys, Im not a mechanic but am keen to learn about my car

[stevolew]

If you blow this pic up, between the suspension spheres there is a "oval" white coloured bit with a yellow dot on that is what you are looking for.

[Rob Bell]

Mk1 speedometers use a mechanical drive - the later cars with 3 cables. The cable that inserts into the gearbox is the one that fails - and is reasonably straightforward to replace. My how to can be found here: http://mgf.ultimatemg.com/group2/DIY/Sp ... /index.htm

PS Stevolew - I really like the way you have preapred and detailed the engine/transaxle/subframe above

[Plezier]

Yes you can access it fromt eh top. It's a bit of a reach and there is lots to get around but yes you swap it from the top. Had to change the rear section on the 97 MPi the other month.

[kevinarbury1]

Cheers all for all the help received! I am going to borrow a set of axle stands and jack from a mate at work and I'm gonna get under it and have a poke around!

If its not the speedo cable or drive gear thing, is it possible there could be a problem inside the gearbox itself??? how does the gearbox mesh with the speed drive component? Iv seen there is a small white plastic gear and I assume this locates to a specific gear in the gearbox? is it possible the gear in the gearbox has faulted???

sorry for the questions, i just want to get this sorted and its such a great little car!!!!!

[Rob Bell]

I can almost guarantee it will be the gearbox section of the cable. As they say: "common things occur commonly!"

The gearbox has a speedo drive that attaches to the differential assembly. On the versions of the PG1 fitted to the MGF and TF, it is a plastic item, but there are no known durability issues known with it (there is always a first time though! ) Let us hope it isn't that; to access the differential, it looks to me that you have to remove the whole gear set (something I am not particularly looking forward to for when I fit an LSD in the close ratio PG1 G4' for my track car )

[kevinarbury1]

Hi Rob, that sounds great...hopefully!!!! Il be getting underneath asap and having a dig around to see the cable near the gearbox!

il let you now that outcome....

cheers!

[Plezier]

The gearbox end of the cable, which in most cable drive F's seems to be in three parts, well one end ends on to top of the gear box below the chracoal filter thingy on the rear bulkhead the other end in under the cr about 10" in from the front of the rear sub frame. It's a simple push connection.