Buying & Building a Medium Ambulance into an RV – The FAM-BULANCE


I'm still here - just the usual summer family stuff plus some home projects to keep my spare hours occupied.

I've been reading news articles about truck tires that have come off and rolled down the road, wiping out anything they came close to, and it got me worried. Back in the old days, when I restored 2 1/2 ton 6x6 trucks, tightening the Budd lugs was easy -- if you wound them down with a 1/2" impact, you could get them off with a 1" impact. The military approach was definitely straightforward - the motor pool sergeant told me that if I ever tightened them by hand, pull on the wrench until I heard it go "Crick" twice, then they were tight.

Having installed Alcoa aluminum wheels, I now had a different lug nut system, and even though I continued to use my 1/2" impact to tighten them, I didn't have any confidence in the final torque. Alcoa calls out 450-500 ft-lb for my M22 studs, which I knew I could do with my 66:1 torque multiplier. The drawback is that the math says that the torque multiplier needed an input of only 6.8 ft-lb to give me an output of 450# - assuming 100% efficiency! I knew it wouldn't be 100%, but what would it be? I can measure low torques, but the accuracy of the final result was totally unknown.

At that point, I decided to keep the torque multiplier as an on-board emergency tool, but to start using a torque wrench for the final tightening.

lug nut torque.JPG

After some digging, I tracked down a slightly used Proto 600# torque wrench. I could have purchased a Chinese wonder, but I like Proto, and the furnished calibration certificate states accuracy to 3%. Good enough for me.

I figure the odds of something ever happening are low, but I now have the peace of mind in knowing that I did my best to comply with Alcoa's requirements.

DSCN5881.JPGlug nut torque.JPGDSCN5881.JPG


The photo inserting function is a little cranky tonight, so you get twice as many opportunities to enjoy them....


New member
How is the hose line Air Conditioning install going? Details please. I am wanting to do something cooling the box since I live in the south . Trying to avoid cutting into the roof for a rooftop AC.


It was easy to ship - they wrapped the case in cardboard and stuffed it in a mail box. Thankfully, Proto has a very good case!


How is the hose line Air Conditioning install going? Details please. I am wanting to do something cooling the box since I live in the south . Trying to avoid cutting into the roof for a rooftop AC.
Hoo boy -- I could spend a long time on this one.

My buggy has 4" clearance goung through my garage door, which meant no simple (and cheap) RV AC. Instead, I decided to install the standard ambulance stand-by AC. Built by Hoseline, it includes a dual evaporator with a hot water heating coil and also often includes a 120 volt hesting coil as well.

Great idea, until I got out my Hoseline catalog and a tape measure. My Medic Master uses a very narrow evaporator, and there was very little room for a dual coil.

On to PLAN-B. The module came to me with a small compartment for an IV bag heater. I measured, and I have room to eliminate the IV bag compartment and stuff in an evaporator there.

Let me dig through my notes, and I'll expand on this.


Expedition Leader
Bob, we should just combine our builds and publish all our emails and everything would be covered for both! 😁

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New member
Please do! Ya got a customer right here!
I am struggling with the rooftop AC idea. I would love to run a Minisplit. But it is not meant to be installed on something mobile. I want the roof to be available for rack , storage and solar panels.


Several problems (challenges?) with adapting a mini-split AC to an RV include
--Where to install the condenser unit
--How to protect the condenser from vibration.

Where is the first challenge, but vibration protection goes hand in hand:

. Hoseline offers two locations: under the body (bottom mount), or over the cab (top mount). Take a look at a Hoseline undermount AC condenser, and I think something comparable might be brewed up for a mini-split. The GOTTCHA is that the equipment will be installed in a fairly rugged location. Simply using a few pounds of Tie-Wraps to hold things together may cause problems from Tie Wrap breakage or actually softening from the temperatures. This location would expose the AC condenser to a continuing barrage of dirt and stones, and the condenser fins may have a significantly shorter life.

cond inst.jpg

Take a look at how hydraulic lines and hoses are protected where they cross in hydraulic applications, and you'll see a metal clamp around each hose, with the clamps themselves bolted together.

It may also be possible to build your own top mount installation. The location will still have vibration problems, but the location will be cleaner, and you will probably have fewer dirt/stone problems.

top cond.png
If you're lucky enough to wind up with an ambulance with some space between the cab and the module, it may be possible to mount a Mini-Split there. Vibration isolators are available from many on-line sources - just remember that the isolator rating is based on the weight of the isolated mass, and on the vibration environment. This would probably be my preferred location.

Another thought is the truck cab AC units that are becoming more common on long haul trucks. They use a condenser mounted on the rear of the truck cab, with a separate compressor module.

Pro-Air Company manufactures a 120 volt standby unit for ambulances that has a fairly compact compressor/condenser unit. I think I attached their installation manual to this posting.

What's the answer? I wonder if you couldn't really massacre an Off The Shelf Mini-Split AC condenser and just relocate the pieces. Using a used Hoseline condenser in combination with the Mini-Split's other components may be an answer.

More food for thought might be to start with a used rooftop AC, and slice it into components. RV AC units do more with less (one fan motor with two blowers), but with a pile of used RV units, it might work OK. One GOTTCHA to watch for is that RV units typically use a capillary tube instead of an expansion valve, so the end result may be more prone to plugging.

More thoughts to follow


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New member
Thanks for the info! My rear module Air Con condenser is mounted under the box now. Might could tap into that one. ..

But I like the idea of leaving the stock Air Con alone and using a stand alone. Our summers in the south are brutal so a Air Con system will have to be a good one. Also considering running it off solar or a generator eventually, so need one of the power saver units or one that does not draw too many amps.

Probably overthinking it. But I want to do it right.


The engine-driven AC is designed to cool the module when it's loaded with people and a door open. It will definitely do the job if it's correctly charged. Virtually all of the 120 volt stand-by AC systems run about 11,000 BTU. This lets them operate on a 30 amp circuit.And that also matches well with 2800 - 4000 watt generators.

When you think about it, a 14x8x8 space probably only needs about 5000 BTU, so an 11,000 BTU unit should be plenty for your module, particularly if it's painted white.


It's amazing what can be done - years ago, a friend of mine needed an air conditioner for a railroad passenger car that he was converting to a railroad museum car. He needed AC for this car (sealed windows), but wanted a unit that was more efficient than the state-of-the art for passenger car AC - plus one that was a lot tighter with lower Freon usage.

After some tape measure time, he scrounged an old semi-trailer refrigeration unit, and literally sawed it to pieces so it could be stuffed under the car. It actually did pretty well, plus it was diesel instead of propane to boot.

So - if you want to saw up an RV AC, or a mini-split, believe me when I say that its probably been done before.

And that, folks, could result in both an AC system, and a great over-a-beer story!