AC Clutch

Rick Jay wrote:

dougrainer wrote:
NO Class A motorhome has a dedicated fuse for the AC clutch. There IS a fuse for the compressor/clutch, but the wiring going thru the Various Tstats and Lo and hi pressure switches will melt before the fuse for the Comp/clutch blows if the clutch is the cause of a short. Doug

Hi Doug,

Ok, thanks for the clarification. The majority of my A/C work has been on cars and I only had to change out the compressor on my moho, I didn't have a "fuse/no voltage" issue. I just assumed that since the manufacturers usually do it on cars, and the compressor is mounted on the engines of the class A's by the manufacturers that.... Oh well, that's what happens when you ASSUME! LOL

So, there is a fuse, but it also protects the other devices in series with the clutch. Is that correct?

Thanks for the clarification! Your wisdom on these boards is much appreciated! :)

~Rick

Yes, there is a fuse. Usually, On Ford/Chevy/Workhorse/Freightliner/Roadmaster, They use a Comp fuse usually at the Chassis builder fuse control since the chassis builder installs the compressor, but the controls that I mentioned are thru the same fuse. So, if you suspect a Clutch short, you will usually find one of the smaller gauge wires to the various pressure switches melted or burnt. It would not hurt to install an inline 20 amp fuse between the Clutch and the clutch harness. MOST follow this rule, but there are exceptions. But, there are wiring that will not melt and the comp fuse WILL blow. You can usually look at a clutch if you suspect a clutch short and it will show extreme heat build up as it was failing and the clutch plates got red hot before it failed and shorted out. Also a distinctive smell if it happened recently. Doug

dougrainer wrote:
NO Class A motorhome has a dedicated fuse for the AC clutch. There IS a fuse for the compressor/clutch, but the wiring going thru the Various Tstats and Lo and hi pressure switches will melt before the fuse for the Comp/clutch blows if the clutch is the cause of a short. Doug

Hi Doug,

Ok, thanks for the clarification. The majority of my A/C work has been on cars and I only had to change out the compressor on my moho, I didn't have a "fuse/no voltage" issue. I just assumed that since the manufacturers usually do it on cars, and the compressor is mounted on the engines of the class A's by the manufacturers that.... Oh well, that's what happens when you ASSUME! LOL

So, there is a fuse, but it also protects the other devices in series with the clutch. Is that correct?

Thanks for the clarification! Your wisdom on these boards is much appreciated! :)

~Rick

Rick Jay wrote:
yobie,

Do you have a gauge set for the A/C? Without one, you're kind of shooting in the dark. If you have one, what are you reading on the gauges? If you don't have one, buy the gauges. Not that expensive and well worth it, in my opinion. I can't imagine trying to do A/C work without a gauge set.

If the system is low on refrigerant, as you know, the low pressure switch won't allow the clutch to engage. However, I've always been able to get sufficient pressure in a low (evacuated) system just by connecting the tank of refrigerant to the low pressure side and opening up the valve on the gauge set to let the R-134 in. Within a minute or two, the compressor will kick in. It doesn't take much refrigerant to turn on the low pressure switch. In cooler weather, I'll put the tank in a tub of hot water if the tank is running low.

As mentioned above, you can also put it in through the high-side, but you have to be very careful NOT to leave it connected if the compressor kicks in. Otherwise the compressor will pump & pressurize your tank. I've never needed to do that as I mentioned above.

I wouldn't jumper the switch until I knew what I had for pressures in the system.

I can't speak about your system, but I think every vehicle I've worked on had a dedicated fuse for the compressor clutch. I could be mistaken, but I can't think of a situation where that wasn't the case. Are you sure there isn't a fuse in your system that's blown?

Good Luck,

~Rick

NO Class A motorhome has a dedicated fuse for the AC clutch. There IS a fuse for the compressor/clutch, but the wiring going thru the Various Tstats and Lo and hi pressure switches will melt before the fuse for the Comp/clutch blows if the clutch is the cause of a short. Doug

The DIY cans often come with oil in them. Charging with them can result in to much oil in the system.

Auto stores like Autozone, etc will lend you a set of gauges for your AC system.
They also make an inexpensive 12 volt voltage detector for you to check each wire to determine if there is power to the wire. These make it fairly easy to check the wiring on a vehicle. Don't forget the possibility that the wire has been broken or chewed by rodents if you can't find a fuse that supplies voltage to the compressor.

Looking at your picture, is that Oil or dye on the cooler and hoses. If oil I really would not try to jump the system till I service the system with the right amount of Oil. It does not take much to junk out a compressor with not enough oil.

I just replace a compressor that blew a O-ring at a fitting and most of the oil if not all of it came out. This person had clean up the mess and replace all the hoses and drier and came over to have it vacuum and service. He never said that what happen when ask.

I add the required oil amount for the new hoses and drier. He came back on this past Tuesday with no cooling. The compressor would not turn over. He pulled it off and we could not turn it at all when clamped in the vice. I took it apart and found the pistons has done a number on it. That when he told me it had blown and oil was every where. He did a very good job of cleaning it up.

This man keep the RV very very clean so you would never suspect that a hose had blown.

All I am saying is if that is oil, pull the compressor and drain the oil and then put the right amount back in it, then put back on and new hoses if required and vacuum it down and recharged.

Rick Jay wrote:
yobie,

Do you have a gauge set for the A/C? Without one, you're kind of shooting in the dark. If you have one, what are you reading on the gauges? If you don't have one, buy the gauges. Not that expensive and well worth it, in my opinion. I can't imagine trying to do A/C work without a gauge set.

If the system is low on refrigerant, as you know, the low pressure switch won't allow the clutch to engage. However, I've always been able to get sufficient pressure in a low (evacuated) system just by connecting the tank of refrigerant to the low pressure side and opening up the valve on the gauge set to let the R-134 in. Within a minute or two, the compressor will kick in. It doesn't take much refrigerant to turn on the low pressure switch. In cooler weather, I'll put the tank in a tub of hot water if the tank is running low.

As mentioned above, you can also put it in through the high-side, but you have to be very careful NOT to leave it connected if the compressor kicks in. Otherwise the compressor will pump & pressurize your tank. I've never needed to do that as I mentioned above.

I wouldn't jumper the switch until I knew what I had for pressures in the system.

I can't speak about your system, but I think every vehicle I've worked on had a dedicated fuse for the compressor clutch. I could be mistaken, but I can't think of a situation where that wasn't the case. Are you sure there isn't a fuse in your system that's blown?

Good Luck,

~Rick

Thanks! I've checked every fuse and every relay. There is no dedicated fuse to to my knowledge to the clutch, which is very weird. I've read every manual from Holiday rambler and ford and they do not specify a fuse for the clutch. Either way I have gone trough all 100+ fuses and all are clean and working. Only thing I can think of is there is a possibility there is an inline fuse somewhere under the dash.

I did try charging on the low port hoping it would take enough to jumpstart the compressor. It didnt take any r134 even after 15 minutes.

Again I really appreciate all the advice. I do have a gauge, but might be worth buying a real one vs just a low port gauge.

yobie,

Do you have a gauge set for the A/C? Without one, you're kind of shooting in the dark. If you have one, what are you reading on the gauges? If you don't have one, buy the gauges. Not that expensive and well worth it, in my opinion. I can't imagine trying to do A/C work without a gauge set.

If the system is low on refrigerant, as you know, the low pressure switch won't allow the clutch to engage. However, I've always been able to get sufficient pressure in a low (evacuated) system just by connecting the tank of refrigerant to the low pressure side and opening up the valve on the gauge set to let the R-134 in. Within a minute or two, the compressor will kick in. It doesn't take much refrigerant to turn on the low pressure switch. In cooler weather, I'll put the tank in a tub of hot water if the tank is running low.

As mentioned above, you can also put it in through the high-side, but you have to be very careful NOT to leave it connected if the compressor kicks in. Otherwise the compressor will pump & pressurize your tank. I've never needed to do that as I mentioned above.

I wouldn't jumper the switch until I knew what I had for pressures in the system.

I can't speak about your system, but I think every vehicle I've worked on had a dedicated fuse for the compressor clutch. I could be mistaken, but I can't think of a situation where that wasn't the case. Are you sure there isn't a fuse in your system that's blown?

Good Luck,

~Rick

you really do not need the compressor running to put freon in the system. Put it in the high side, can upside down and do not power on the compressor. Let set for 10 minutes or so then, run the system for the last few ounces thru the low side vapor only. If it will not take freon then you have a bad leak and a lot of air in the system.

oldave wrote:
Looking at your picture , a little farther to the left is a grey plastic
connector , behind that connector is a little square box ( thermostat )
This has a tiny copper tubing that goes into the evaporator coil ,
it's job is to keep the coils from freezing up by cutting 12v to the comp .
Two wires connect to it and can be knocked loose or the thermostat can
go bad .
Try the paper clip there and see if you get 12v to the clutch .

Thanks will try!