How to change the light Plug Controller/Relay top top the 7.3L IDI Diesel

The light plug system on the 7.3L IDI diesel is regulated by a light plug relay and glow plug controller. When the ignition key is switched to the "run" position, the relay is activated, sending out power to the bright plugs. The light plug controller is basically the timer because that the system, turning off power to the relay (and thus glow plugs) as soon as necessary. Some symptoms the the light plug controller and or relay space faulty include: light plugs no receiving power, no functioning properly, functioning intermittently, or the glow plug relay clicks rapidly and also glow plugs will not continue to be on.

Applicable Models: 1988 - 1994 7.3L IDI Diesel 7.3L IDI bright Plug Relay: Motorcraft DY861 7.3L IDI glow Plug: Motorcraft ZD9, Ford F2TZ-12A342-A 7.3L IDI glow Plug Controller: Ford E7TZ-12B533-A, Wells 19462 (includes glow plug relay)

The light plug relay is the much less expensive item, so it"s no a negative idea to change it alone and also see if it fixes the problem. If the glow plug system proceeds to malfunction, replace the entire controller. Also check for loose wires, shorts, and make sure the system has a great ground before replacing the controller, i m sorry is a reasonably expensive item. After instead of the controller, the is recommended that the bright plugs be changed as well.

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• Disconnect the an unfavorable battery cables indigenous both batteries.

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• On naturally aspirated engines, the light plug controller is mounted to the rear of the entry manifold straight behind the CDR valve. On turbocharged IDI engines, the controller is placed to the passenger next valve cover. Remove the waiting cleaner and also place a clean rag end the intake.

• Disconnect the connector because that the wait-to-start irradiate (blue wire) and remove the bolt that grounds the controller to the engine block.


• eliminate the nuts indigenous the terminals on the bright plug relay for the two big yellow wires and little red wire that attach to the electrical harness.

• remove the seed from the stud at the tip of the busbar and then the two brown wires that cause the light plug harness.

• at this stage, all wires that result in the electrical/glow plug harness need to be disconnected native the glow plug relay/controller, yet there need to be number of wires that still affix the light plug relay come the controller chin - this don"t have to be removed.

• Extract the bright plug controller by removed the two bolts that connect it come the entry manifold.


• If friend are simply replacing the relay, remove the remaining wires after you have actually written down or significant the terminals in which castle belong, then change the old relay v your brand-new one, double checking that all wires space hooked up appropriately (see diagram below if in doubt).

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• If you space replacing the entire controller, install it in the turning back manner the the old to be removed.


• The picture at left is a diagram for the glow plug controller and also relay. Check, twin check, and also triple examine that your wires are installed correctly, as you may damage the controller if anything is not installed correctly.

• do not depend on this diagram alone - in the event that the truck has been operated on previously, part wires may have actually been changed with various colored ones. Make your very own diagram, and use this one as a referral to that.