Fan Speed

[davidbrady]

Hey Al,

The first thing to check is the fuse in the remote engine start cabinet in the engine compartment (I think the fuse is labeled "ignition"). If the fuse is blown, the fan will default to high speed.

Under the 'fan off' condition, the S-60 fan should run from 200 to 500 rpm for engine speeds from idle to 2100 rpm. When the dash AC is on, or when the fan override is on, or when the coolant temp is above 200 deg F, the fan should attempt to run at a max rpm of 1800. This is accomplished by a pulse-width modulating (PWM) valve mounted on the engine door framework in the vicinity of the AC air compressor. This valve controls the fan speed. The PWM has a 3 wire connector going to it. If you disconnect this plug, the fan should go to 1800 rpm regardless of the other switch settings (fan override, etc).

There should be 3 signals going to the PWM: Ground, Power (12V via the ignition key), and a PWM Fan Ctrl Signal (from the DDEC ECU). The fan speed is controlled by the DDEC based on engine coolant temp, fan override, chassis AC, and probably more. In the absence of input signals, the PWM should default to 1800rpm. This is a fail safe feature so that you get cooling if there's a wiring fault; i.e., unplugging the connector should result in a change in fan speed unless, of course, you have the dash chassis AC or fan override enabled.

The Hayden hydraulic cooler is expensive and has a lead time for manufacturing. The Hayden cooler part number is 027026. I'd try:

1) Berendsen: 704-588-7723; $540.00 for 027026; 3 to 4 weeks
2) Livingston & Haven: 704-525-7910; $340 for 027026; 3 to 4 weeks (Pays to shop around)

I think the cooler is entirely constructed of brass so if the leak can be identified you may be able to repair it by having it soldered.

WaGu->Document Library->Models->LXi->HaydenCoolerCore_LXi.pdf