I have burnt out one of the resistors in my 18 volt 3 pin battery charger. Is the circuit diagram available so that I can identify and get a replacement resistor ?

http://www.xantrex.com/documents/Discontinued-Products/HF12-1200SU.pdf

Possible suspects are:
1. A severely drained battery.
2. Check battery terminals for damage or corrosion, check the battery cables at "BOTH" ends for loose, corroded, or broken connectors, "INSIDE" and outside the cable harness, perform connector wiggle test and check cables with an ohmmeter if necessary.
3. Faulty main circuit breaker and or connections.
4. Faulty ignition coil and or connections.
5. Faulty spark plug, oil or gas fouled, wrong heat range or service type, wrong gap, loose in the cylinder head, broken electrode or insulator.
6. Faulty spark plug cables, leaking or broken, internal damage.
7. Faulty ignition module, switch, CKP, MAP, CMP, sensor and or any connector in the ignition circuit could have corroded, loose, or broken pins/sockets
8. Burnt exhaust valve or air leak in the exhaust system.

Without a circuit diagram or another actual unit to look at it is very difficult to identify burnt out resistors. Even harder is finding out why it burnt out because most of the time a resistor only burns out if overloaded due to other circuit component faults.

Can you (carefully!) measure the volts across them with a load (battery) and then the current through them by disconnecting one end, and if the charger is still working OK then they are V/I ohms, choose nearest value. 10k sounds very high, are you sure they aren't 1 ohm or less?

Bad connections on the battery posts is most likely. If the circuit breaker was bad you'd get nothing at the battery . The charger voltage is 29 volts when not connected to the batteries. 26 or more when connected and on.

It is usually a current limiting resistor anyway... so I would think that about 100 Ohms should be all good, you generally need about 250 - 300mA to charge ya batteries. It is simple Ohms law calculation.

If you're only reading .18 volts DC at the charger itself, then it's time to replace the charger.
It's probably some inexpensive Electrolytic Capacitors inside the charger that have bit the dust.

Here's info about Electrolytic Capacitors,
1.http://en.wikipedia.org/wiki/Capacitor_plague

2.http://www.capacitorlab.com/visible-failures/index.htm
Both sites relate to computer motherboards and computer power supply's, but know, that there has been a problem with 'Caps' for all kinds of electronic components, no matter what they are, therefore these same visual signs of failure apply. (Sorry about the run on sentence!)

3.http://www.absoluteastronomy.com/topics/Capacitor_plague (Read the entire article, and my statement above will become more clear)

I have the same exact problem in a 12 volt Lincoln battery charger. Burned resistor in R5.

I need the same, but found a Makita multi-voltage charger and have been able to use it. The package says It is for Makita batteries only. HItachi also makes a universal battery charger. I found both at my local Lowe's. The Makita was originally $69, but was marked down to $25. The Hitachi was around $70. You can find either one for good prices on Ebay or Amazon.

Good luck!