I just received this email from BilliBob here at the Forums. Can anyone else confirm this? (Not to cast doubt, I just wanted to see if anyone else recognizes this.)

From BillyBob@ShopForum:

Check the 603 FSM later glow plug relays (after 1989) do not have a fuse and are essentially equipted with an internal circuit breaker, it is not externally resetable but resets itself. If you have an short circuit at a GP or the wiring to these you would in theory keep tripping it. Alternately the circuit breaker could have failed or some other element inside the relay. This info is detailed in the FSM 15-705 to 711. The thing that you could do is to disconnect the GP harness fron the relay and then cycle the ignition key to reset the circuit, then you can use a multi-meter, a 12V bulb or LED to test if the relay is providing voltage to the GPs, attach one wire from the bulb to engine ground and the other lead to one of the 6 pins in the relay. Cycle the key and you should be able to measure 12V or the bulb should light up, check all six pins this way. If all six pins show good voltage its not the relay. You can then open the 6 pole connector shell on the GP harness, attach one of the six female sockest to the male pin in the relay box. Cycle the ignition key and check for voltage at the pin. Do this adding a single GP wire socket to a male pin in the relay cycling the ignition key each time. If one of the glow plugs or its wiring is at fault the relay will trip and you won't find voltage at the male pin. Once you isolate the individual GP or its wiring that is short circuiting you can replace or repair it.

The serpentine belt tensioner should be tight if properly configured, if the belt is not properly routed usually it seems too short but perhaps it is incorrectly routed and is loose. The spring is attached at its bottom to a pin on the tensioner and at its top to a pin in the black plastic cam block. With the tensioner bolt that holds the cam block in place romoved and the belt loosened you should be able to move and observe the entire tensioner arm/pulley and rock it from side to side for free movement. The spring could be broken inside its plastic sleeve. The cam block should pivot freely on its pin. I assume that you've checked each of the pulleys on the PS, Alternator, AC and water pump to assure that they are all freewheeling. I had my AC compressor seize and it smoked the belt and made a hell of a noise.