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After market Ac units

Posted By: HarleysandVans

After market Ac units - June 16th 2019 10:28 am

So my 77 GMC G15 Gypsy didn’t come with factory AC so I was looking into aftermarket AC units that run off the electric. To be honest I’m in over my head I’m trying to make heads and tails of this shit and figure it what I need. Are there any full kits anyone can suggest? Also I’m probably gonna have to upgrade my charging system too right? How’s that gonna work, just an upgraded alternator?[img]https://imgur.com/gallery/0r5ydde[/img]
Posted By: Reed

Re: After market Ac units - June 16th 2019 10:07 pm

You would have to do some SERIOUS upgrades to your charging system to run an all electric AC system. Almost all automotive AC systems use the engine to drive the compressor.

I recommend grabbing all the engine compartment parts form a later van with AC and then adding an aftermarket evaporator and ducting in the cabin.
Posted By: wrcsixeight

Re: After market Ac units - June 17th 2019 5:38 am

Do you know how much wattage or amperage the electric AC units you are looking at consume?

Just wondering, I know the lowest amperage window shaker style 115vAC AC unit is ~450 watts which is 35 amps at 12.8vDC. One must add ~15% more load to that for inverter inefficiency.

My '89 Dodge's Hvac newish blower motor on high speed is about 15 to 17 amps

I have an alternator rated at 50 amps idle and 120 amps maximum.
My engine, just to run fuel pump and ignition( not including field current to alternator) consumes 12.2 amps at 2K rpm. and 8.2 amps at idle. Headlights are another 15 amps. you can see that sitting idling at a red light at night blower motor on high I do not have much amperage left over to keep the battery from discharging

While my engine has Dual V pulleys and belts, i only run one belt as My AC is Inoperable and one or the other V belt is too tight or too loose, even if I get a matched pair. It will start slipping at about 75 amps when damp, unless I really tighten it to the point I am stressing out the water pump bearings.

It is said any amperage reqirement over 90 amps requires Dual V belts or a serpentine belt.

Many high amperage alternators, do not advertise the fact that their low rpm output is worse than their lower rated counterparts. This is not true ofthem all, just be wary of their claims, and know that their rating is only at higher rpms when still cold. Once they heat up they can produce way less safely.

I have found speeds under 25mph that my maxed out alternator's stator( casing) can quickly approach 220F which is the tipping point, yet 65MPH and maxed out at 120 amps, it stays below 140f. The point is that Idling or slow speed driving with a maxed out alternator heats it to the danger zone quickly.

You would likely have to run dual capable alternators to effectively and reliably power and electric AC unit.
Posted By: HarleysandVans

Re: After market Ac units - June 18th 2019 11:40 am

Yeah maybe I’ll run get a generator and run ac off that, I’m only pushing a straight 6 250ci engine I’m still trying to find out about the van as it’s so old finding service literature has been a hassle, but I don’t think adding more pulleys would be smart, the engine runs great for a ‘77 so I wouldn’t wanna [censored] that up
Posted By: Xplorer_Loco

Re: After market Ac units - June 18th 2019 12:43 pm

Our van, a 5.9l V8 360 engine, has a 65 Amp alternator. When stopping at a red light for example with the headlights on, I put the AC on low, otherwise I am starting to discharge the battery. Not much, and not for long, and recharge quick again once driving again, but still...
The engine and its accessories to run, they use about 35 Amps if I am not mistaken. So our 65 Amp alternator, at idle, just manages to produce that. But as I said before: with headlights on and/or AC, etc., the 65 amp alternator is no match when at idle. It does a great job when driving though, even at slow speeds. We will upgrade soon to a 100 amp alternator. At idle it will produce just enough for the engine, headlights, AC to operate without having to draw power directly from the battery only. (AC probably on low as well.)
Thought of a dual alternator, both 100 amps, but then again: dual belt? Weight and weight distribution of the alternators affecting the engine? Etc. So might just go with a single 100 amp alternator swap and live with that.

PD: On modern cars it is less pronounced as the computer regulates it pretty good, also reduces AC load automatically when idling, and similar things. It seems not to be an issue, but truth is they "suffer" from the same: not enough amps when idling. Its instrument needles just don´t show that trend as they (with their computer) know that it is just temporary and will get back to non-idle again soon. If not (after very long idle) they will show.
Our elder vans are just more... mechanical.
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