M1010 w/12v get A/C working?

[M1031CMT]

We have an M1010 which was converted to 12v by a police agency before we bought it. To start off with, the electrical system was pretty messed up when we got the truck. The previous owner (who had bought it from the PD a little while before) said the truck ran well, but after getting it, we found that the batteries would drain over the course of 12 hours.

Ended up finding that the wiring under the hood was wired by someone who had no idea what they were up to. Somehow they ended up grounding the positive connections just about everywhere. They had even ran a jumper from the 12v connections to the GND connections on the block on the firewall. We had always seen a few sparks in the engine compartment if we had the hood up and started the truck. The PD also had some sort of switching system in the cab as there was a harness with about 30 wires cut off just sitting by the 4x4 shifter (we traced them back to a lot of cut connections in the engine compartment which we ended up pulling out). But it seems that we have finally found all the messed up connections and also installed a kill switch between the batteries and system to make sure the truck starts. So far the batteries no longer drain by the next day. But I am just babbling, onto my question.

Has anyone who has an M1010 converted to 12v been able to get the A/C unit in the back working? As I know the unit was made to work on 24v.

Our truck still has the A/C unit as well as the compressor on the engine. If you turn on the A/C unit (even with the engine running), nothing happens. The compressor on the engine never kicks in. Only thing that works is just the fan for air circulation. But the fan is not very strong, so I am guessing the unit is getting 12v which is enough to get the fan turning, but not as fast as you would if it had 24v.

I know that the A/C unit works with 24v, so I am thinking if I installed a 12v-24v converter that I might be able to get the system to work (which would be nice to cool my fat butt in the winter). Been looking at the wiring diagrams, but since the wiring in our truck has been hacked up a bit (well more like a lot), it is hard to figure out what is what without another truck to compare it to.

Was just wondering if anyone else has tried or looked into the idea?

 

[drgreg]

I think the 30 wires, by the shifter, are correct. They were for a diagnostic plug located just under the dash.

 

[captw]

M1010 A/C on 12V

Hi Gilles...you need to send a PM to C15TA on this site...Barry's M1010 was also converted by a police agency to 12v, his battery also drains if he leaves it connected, but I'm pretty sure his A/C does work and blows cold...W

 

[M1031CMT]

I think the 30 wires, by the shifter, are correct. They were for a diagnostic plug located just under the dash.

Actually the diagnostic plug is still there. Sorry, should have been more clear. This was an additional set of wiring. Likely to control some extra light system they had installed. There was some odd bracket sitting beside the 4x4 shifter which probably held the controls. We ended up moving it and modifying the bracket to hold a CB radio. You can see in the below pic that the plug is still in place. But thanks for the idea.

..you need to send a PM to C15TA on this site...Barry's M1010 was also converted by a police agency to 12v, his battery also drains if he leaves it connected, but I'm pretty sure his A/C does work and blows cold...W

Okay thanks. Hopefully he chimes in if his unit is still working while on 12v.

 

[41cl8m5]

I'm not sure about the 12v deal but I found there is a relay that is always on if the switch on the black out lights is left in the on position. That switch must be in the off position if the truck is not in use. It goes for both black out and service lights positions. It only seems to be an issue with the M1010. If you look at the operators TM, the instructions say to make sure the switch is in the off position if the vehical is not in use (or something like that).

Try to find someone that follows that with the other chevy cucvs. I was told it had to do with the addition of the ambulance box. I stile have not looked that deep into it sense just moving the togal switch to the off position fixed my battery drain issue. Last time I started the truck I moved the the swicth to the service position and it fired right up and that was after being dormant for 2 months. Before using the switch the next morning it would be dead. The batteries on my m1010 are old and in need of replacing but they seem to get the job done at this point.

hope this helps

 

[captw]

M1010 12v conversion and battery drain

hey 41cl8m5...thanks for that info...interesting....I'll forward the info on to my buddy...I know that on my M1008, the swiches stays in the service position and no problem...W

 

[41cl8m5]

My M1009 has no issues either captw

 

[m1010plowboy]

Hey neighbour, It's warm enough over there for AC? Nice

I haven't 'serviced' mine yet because of the lazy compressor and the Freon / R12 refrigerant , re-charging issue. My 'system' needed to be charged and the compressor re-built so I removed the drive belt and haven't looked back....until now.

We had one hot day last year so watching you get yours working would be great inspiration.

We have a similar challenge with the 'heater' because it runs a 24v ignitor system and we're on 12V.

Do you have 24V to the fan? Can you get on the power wire going to the unit and check volts?

There's lots of data on "How to re-charge A/C" if you haven't looked at that yet.
Recharging Your Car's Air Conditioner

I do know that if it's not charged the compressor won't compress and the evaporator won't evaporate. Let us know what you find out!

 

[K9Vic]

m1010plowboy, your link is to R134, the A/C system is R-12 and you cannot get that anymore. The only option really is Freeze12 or other R-12 replacement products that can be used without changing the compressor and seals to allow R134. I have put Freeze12 in cars before and works well, but it is not easy to find.

 

[unaffiliated]

You don't have to change the compressor to run R134. I have been converting Mercedes to R134 for years just by evacuating the system of all R12 and pulling system into a vacuum for at least an hour, add 2 or three ounces "Frigi-Quiet" a/c oil made by BG Chemicals and the charging with R134. I don't change anything, not the seals, compressor or anything. YES, the seals probably/maybe go to leaking later, but you can replace them as needed. This way you can see if the system is even gonna work before you go through all the trouble of changing every single o ring only to find the compressor is bad or some other problem. The BG a/c oil is compatible with all other a/c oils.

 

[lavarok]

I'm not sure about the 12v deal but I found there is a relay that is always on if the switch on the black out lights is left in the on position. That switch must be in the off position if the truck is not in use. It goes for both black out and service lights positions. It only seems to be an issue with the M1010. If you look at the operators TM, the instructions say to make sure the switch is in the off position if the vehical is not in use (or something like that).

Try to find someone that follows that with the other chevy cucvs. I was told it had to do with the addition of the ambulance box. I stile have not looked that deep into it sense just moving the togal switch to the off position fixed my battery drain issue. Last time I started the truck I moved the the swicth to the service position and it fired right up and that was after being dormant for 2 months. Before using the switch the next morning it would be dead. The batteries on my m1010 are old and in need of replacing but they seem to get the job done at this point.

hope this helps

You only need to keep the master switch (right one) off when the truck is not in use. There is a relay next to the starter relay for the BO lights in the ambulance body. When the light switch is in the ON position this relay stays energized and will drain your batteries. Leave the switch off when not in use and you will not have a problem. This is a M1010 only issue. No other CUCVS are affected as they do not have the same wiring setup for the lights.

Secondly. the AC unit will require 24v to operate properly. All the dc motors are rated at 24v. There is a relay in the rear compartment that controls the compressor clutch. If that relay is bad or missing it could explain why your clutch is not engaging. There are also several fuses in the rear box that also pertain to the AC system.

Good luck!

 

[M1031CMT]

Do you have 24V to the fan? Can you get on the power wire going to the unit and check volts?

There is definitely not 24volts going to the fan, for as I said before, the truck was converted to 12volts. There is no 24volts in the truck. The fan in the unit works, but it is slow, meaning that it is getting 12volts which enough to get it to spin, but not at full speed.

Secondly. the AC unit will require 24v to operate properly. All the dc motors are rated at 24v. There is a relay in the rear compartment that controls the compressor clutch. If that relay is bad or missing it could explain why your clutch is not engaging. There are also several fuses in the rear box that also pertain to the AC system.

Good luck!

Great. I was wondering where the relay was located. The wiring in the back was messed around with as well, so it might be disconnected. Though even if it was/is connected, 12volts isn't enough to make it work.

After looking through the schematics a bit it does show that the A/C unit is made to run solely on 24volts. I though that maybe there was a chance it was tied into the 12volt system of the truck.

First step is going to be getting a 12v-24v converted wired into the truck. We have a couple of military made 12v-24v converters somewhere in storage. Will have to go dig them out.

Once I check the wiring and apply the proper voltage we should see the compressor kick in. After that if it does not work, then it is likely that the system needs to be charged/recharged.

 

[C15TA]

Hi Gilles
My truck has been converted to R134A so that issue is settled. I did try the air and it blew cold but I didn't pay attention to how fast the blower speed was. It may be still 24V while the truck has been converted to 12V by the Eden Vermont Police. My batteries do go dead if left more than a couple of days. As per previous threads on SS I have checked the blackout light switch. I thought I would get some of these small issues resolved in the winter but I couldn't get the 1010 inside I am going to have to get rid of some of this crap that is filling all my barns. I will see what I can get done in the spring to take it to the MTA show in Sussex. Wilf (Captw) can probably come over and work some of his electrical magic for me.
Cheers,
Barry

 

[Shrapnel]

My M1010 was converted to 12V before I got it but the A/C worked fine. My blower motor and my condenser motors were all 12V. I had to replace the blower motor and look through the catalog at Carquest to find one that would fit right.

All of my lights worked as well, so I'm not sure how much was really 24V in the ambulance box. Even if yours is all 24V it is probably cheaper to replace a few small motors than to get your 12-24V converter. I don't believe the compressor needed 24V at all, as it is just a civvy style compressor anyway. Mine was also converted to 134A easily.

 

[Emmett]

The compressor is 12 volts. The AC unit in the back is 24 volts along with the fuel fired heater and the few outlets.
there was a time when I got two 1010's electrical system working correctly but it took a 'tec rep's" troubleshooting guide to do it.
My headlights would dim about every 3-5 minutes for about 2-3 seconds. After reading the manual I found that it is normal with that bastardized 12-24 volt system.
Needless to say, it is rare to find a 1010 that has a complete and operating 12-24 volt system that works. At best, it's an insane way to seperate the voltages and a PITA to diagnose and repair.