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Engine fan operating Temps
I recently replaced my fan hub clutch, which got me watching the temp gauge and wondering about accurate engine temp monitoring
My 95 Marathon temp gauge is like most other gauges, not very accurate, it is marked up at 195 and the next increments are 220, so when monitoring the gauge it was always a guess at best as to what the actual coolant / engine temp was , i added a Scan Gauge D some time ago for just this reason, Scan Gauge has verified the dash gauge is in fact off showing a higher engine temp than actual.
Scan gauge is great for monitoring temp but does nothing to track fan operation
Last week i added indicator lights for low and high speed fan operation and a high speed fan ON over-ride switch, i now know from the indicator lights when each fan stage is in operation, this is verified against the scan gauge as operating temperatures drop.
In my case the low speed fan engages at 194, this is after driving for 10 -15 miles, if the ambient is in the high 80,s low 90,s the low speed fan will keep operating temps at approx 198/200, if i start to climb and make boost the operating temp starts to increase
My high speed fan will engage at 204 and will remain on until temp falls back to 194, the cycle then repeats itself.
This mod has confirmed for me the operating range of my thermostatic cooling fan switch which is mounted in the crossover pipe from engine to Radiator inlet pipe, my coach is DDEC 111 but prior to fan being controlled by the DDEC,
it tells me exactly what is going on and when, fan operating range is confirmed by temp dropping on Scan Gauge.
High speed over-ride i find useful when i know i am approaching a steep climb i can engage fan prior to starting to climb and also cool engine down prior to stopping engine if i need to
I just did a 500 mile trip in 100 deg ambient ,it was reassuring to see cooling system working exactly as designed.
The spare wires are already in the loom rear to front, the rest was fairly simple.
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3 Replies
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I like that idea! Are you OBD-3 that uses the 2 rear relays? Or OBD-2 that uses the thermostat to control fan. If you have OBD-3 how did you wire them? I thought the same thing with mine putting a couple led indicator lights for when the fan comes on low & high. The relays work off a ground signal to operate fan I could not think how to do that.
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Fan engage settings can be modified so take my temps as what I have experienced and what is called for as normal settings.
My later model XL and now my XLII have a low speed fan cut in at 204, and a high speed fan cut in at 208. Different engine or DDEC vintages may have different settings.
My gauges show what appears to be the correct temps, but with their limited markings and small size all I can say is they look right. However I have run with my DDEC reader connected and it provides a digital confirmation of the temps I stated above.
I do not have to engage my fan clutch when approaching hills. The system does an excellent job and when my high speed fan cuts in, even on the steepest hill on the hottest day I can see the temp gauge peak around 210 and drop quickly before recycling.
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Hi Art
I do not have the 2 relays, just the thermostatic valve in the cross over pipe,
It works great and in my case is a way of knowing that the Thermostatic switch is operating, i can of course confirm fan operation by putting 24 v into wires 291 and 292 and locking the clutch but that does not confirm that the switch is doing the same in operation, now when i see the light for low speed come on i can confirm switch operation.
good Luck
Gordon
Jeff and Lindsay
91 Marathon XL
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