Since I replaced water pump( about a month ago) and put it all back together the tensioner pulley,headlights, engine are all rhythmically pulsing. I did not change the tensioner pulley, when water pump replaced. The battery and alternator check out. What do you think. I can see the tensioner pulley move up and down as this happens. It is all in perfect rhythm

 

Double check your belt routing. If you put wether or not you have a DI or DII it helps us help you.
http://www.roverparts.com/TechTips/s...g_defender.cfm

http://www.roverparts.com/TechTips/s...routing_D2.cfm

 

It is a D1. It is on correctly. I have had problems matching up a belt. everyone I have ordered has been too big. I do not know the problem there. So I was forced to put the old one back on. Just until I can get a new one.

 

www.atlanticbritish.com, I have NEVER gotten a wrong part from them. And I have orderd lots of stuff from those guys.
You will pay more but you will get the correct belt.

 

So you think it is just the belt?

 

Also just aFYI, do not use DHL for residential delivery, they no longer do residential and that was/is one of the shipping choices with AtlanticBritish.
So if you do choose DHL residental your order may be delayed.

 

I would start with the belt. Your belt tensioner may be bad as well but replace the belt first. If that doesnt do it then replace the tensioner and you should be good. but the belt is the cheaper of the two.
Depending on your funds it would be best to replace both at the same time. But if all you can afford is the belt then replace just the belt.

 

On a side note what you have is Lucas Electrical in your Disco I.
The Lights have three positions
1. OFF
2. DIM
3. FLICKER
Welcome to the Prince of Darkness (Lucas)

I just had to.,,,,,, Now it sounds like you ALT is on its way out the diodes are
going bad.
Who checked the ALT ? It is best to check it on the truck,,or
you have a ground wire that is loose.

I have a hand held checker that checks all of the charging system when on
the truck.
See if you can find someone that can do that if that is not what was done.