AC and VH clutches cycling

rictek · **Posted:** Tue Nov 22, 2011 6:54 pm

I barely get any heat for the first 10 miles or so. I noticed the A/C was cycling - even with the A/C button off. Is that normal?
I pulled the fuse for the clutch and it warmed up a little faster. Does that mean the viscous heater is not heating? I see the VH clutch cycling too. But, why would the A/C run cold all the time?

ATXKJ · **Posted:** Tue Nov 22, 2011 7:32 pm

The AC will cycle on in any of the last 3 positions - defrost, defrost + lower air, lower air
whether the button is on or off

- there used to be a couple of threads about fixing it - but most of the photos are gone

warmup depends on how you're driving - idling will not warm up the engine and generally cools it
you have to be accelerating - but then mine warms up in about a mile of driving.
if you're doesn't - check the threads on thermostats.

naturist · **Posted:** Tue Nov 22, 2011 10:02 pm

Diesels are notorious for being hard to get up to and hold proper operating temperature. You may have noticed a lot of big trucks with cardboard stuffed in the radiator during the winter. That is why there IS a viscous heater on your CRD: to speed up the warm up period.

The previous poster is 100% correct about the AC running in those three vent-mode switch positions. If you want the AC absolutely off, you have to use one of the others.

Taking 10 miles to warm up, however, is rather slow. Mine usually reaches operating temp, with the needle about 1 click left of center, within a mile or so. This is at highway speeds, as I live on a main road. If you are spending those 10 miles piddling along in traffic at 25 miles an hour or sitting at lights, that would be why. In cold weather, ie temps below freezing, the engine will not warm up very quickly under those conditions.

rictek · **Posted:** Wed Nov 23, 2011 11:13 am

Thanks- I thought having the button off would disable it. I usually have it in the floor position and didn't expect the A/C to be on.

I kinda putt around the neighborhood and don't really get on it for about 2 miles or so. In Chicago we have been around 30-40 degrees lately. My gauge never goes above the 11 0'clock position. Since I bought the truck in Florida, is it likely they installed a cooler thermostat?

papaindigo · **Posted:** Wed Nov 23, 2011 1:30 pm

No "cooler" tstat; there is only one OEM tstat temp (ca. 175-180). Normal fully warmed up temp gauge reading is dead vertical or about 1 needle width left of vertical; anything left of the 1st tick mark left of center is a sign of the tstat starting to go out; assuming a properly calibrated temp gaugue (see http://www.greendieselengineering.com/f ... st/19.page) and good temp sending unit.

As to warm up time. My diesel experience (2 Dodge Cummins and 3 CRDs including my pre-dump truck encounter one and stoutdog's) is that you can start a cold engine and run it at or near idle darn near forever without any sign of life from the temp gauge (there was even a thread on this some time back that I'm not going to look for). But actually driving assuming a Tallahassee low of mid 20s to upper teens F not garaged; block heater plugged in; w/without viscous heater; good tstat I get detectable heat almost immediately and signs of life from the temp guage within 1-2 miles and a hot cab in 5 miles or so. Same conditions but with tstat failed partially open I get detectable heat almost immediately but the cab takes longer to get hot and of course engine never reaches operating temp. With a good tstat but without that block heater plugged in even with the viscous plugged in I don't get much if any cab heat for 1-2 miles, no temp gauge life for about 3-4 miles, and operating temp is not reached for about 8 miles. Normal 80-90F summer weather temp gauge activity within 1/2 mile and full operating in about 3 miles. This is all on relatively flat terrain, top speed ca. 45mph, average speed more like 15-20mph on a ca. 10 mile commute.

rictek · **Posted:** Wed Nov 23, 2011 7:59 pm

Yeah, it never gets near a tick left of vertical and if I stop at a light, it drops rapidly.

I finally got to the end of 192` thermo mod post http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=50940&hilit=thermostat&start=0

I am going to attempt the mod myself. Outstanding work, kapalczynski !

Wobbly · **Posted:** Fri Nov 25, 2011 8:14 am

It might be interesting to compare the cost of electricity for running an engine heater with the cost of extra diesel used by a cold engine warming up. At $4+ per gallon for diesel, I'd bet that the heater is a bargain. Cost of engine wear of a cold engine is difficult to quantify, but is probably significant.

AC and VH clutches cycling

Who is online