Amplifier Module Symptoms and Remounting
(Classic Range Rover)
Symptoms and Cures Overview
Remote Mounting Kit Instal Procedure
Home Made Solutions
To solve the problem of heat destroying the ignition amplifier module, Land Rover came up with a remote mounting kit to get the part out of the heat. Alternatively, you can remount your own amplifier if you catch it before a problem occurs. This page runs through the symptoms caused by amplifier module failure, and the procedures required to prevent a recurrence.
Symptoms and Cure
The official Technical Service Bulletin on the subject states that typical symptoms are a poor start or non-start, due to failure of the module to control the coil primary current accurately. This can result in dwell angles up to 40 degrees at idle. The excess heat the module is exposed to can cause the insulation to leak out, and eventually cause it to fail completely. This may be accompanied by coil leakage and/or failure. The remote mounting kit (STC1856 -- see drawing at right excerpted from the official Technical Service Bulletin) is designed to fix the problem by reducing heat, vibration and electrical interference. (Before you tear your distributor apart, note that Joel Mahoney traced an intermittent stalling and bogging problem on a loose connector to the ignition amplifier module; see this section for more details).
Campbell reports that the official repair kit consists of another
an aluminum heat sink, along with a 'dummy' module and some pre-made
The new part is mounted alongside the ignition coil on the left fender
area. You remove the old module and mount the 'dummy' unit on the
in its place. This new part just routes power through the distributor
coil and out again to the fender mounted module (which has no real guts
inside it). The official kit, which usually runs about $225 dealer
really solved the heat build-up and failure of the previous modules
and for all.
Remote Mounting Kit Installation
1. Remove distributor from front engine cover assembly, then remove the failed module from the side of the distributor.
2. Fit the red dummy module supplied in the kit on the side of the
distributor in place of the old one, using original screws, ensuring
the blue connectors are a tight fit. Tighten to 1.2 N-m.
3. Refit distributor, ensuring engine is set to TDC and the oil pump drive and rotor arm are in teh correct orientation. (Beforee refitting, Callan recommends that while you have the distributor partly dismantled for this repair, you should check the mechanical timing advance mechanism at the same time).
<>4. Now position the new module on the wing near the coil and
the electrical connetors, running the 3-wire lead from the new module
to the dummy module under the air cleaner.
5. The ignition coil now has to be removed. On vehicles before LH 624781, disconnect the black/white wire from the coil negative termminal, wrap its end with insulation and tie it out of the way --this wire is no longer needed. On later models, do the same withe th red and blue wires (no longer needed).
6. On vehicles prior to LH647645, disconnect the suppression capacitor lead and the positive lead from the coil positive terminal, and replace the terminal with the new 3-blade terminal provided in the kit. Then reconnect the leads to the coil.
7. Dismount the coil, saving the nuts for re-use. Position the new module's heatsink bracket beneath the coil, and re-mount it. Connect the two fly lead connectors to the coil. Tie all the loose leads down.
8. Start the engine and adjust the ignition timing as per the shop manual. Then you are done!!
John Purnell took preventive action on his ignition amplifier module by removing it from the distributor and remounting it to the fender area near the coil. He put a new reluctor plate in the distributor, and routed new wires from it to the ignition amplifier. He used a bent piece of aluminum to mount the latter to the fender beside the coil. If you try this solution, be sure that you restore the 12 volt feed to the coil which can easily be lost in the process of re-doing the wiring harness. For full details of his ingenious solution, see John Purnell's page.