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AC shuts off in traffic (alternator?)

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mouserider

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Charger 1971, 383, tunnel ram, holley efi 2x4, aluminium 3 core rad with double fan (i believe 20amps each) , aftermarket ac compressor, 95A alternator, aftermarket ac rad with push fan

Highway - excellent, voltage is at 12.9. only 1 fan is on, temp 200F
Traffic - 1 fan on, temp goes to 205, voltage 12.3 - 12.4 , ac slowly dying
Traffic - 2nd fan joins, temp 206, voltage 12.1 , ac blowing hot

is this because of alternator not keeping up, or because of higher temp and no airflow?

Thanks
 
Even 12.9 Volts running down the highway is low.
Should be more like 13.5 - 13.8 V
 
Curiousyellow71 said:
Sounds like alternator isn't keeping up.
Click to expand...
i thought so, but then i think, if alternator isnt keeping up, then it should just turn off AC, but in my case i felt like it was slowly dying, not like blowing hot in 1 second.
 
Can you share the name and model # of the AC compressor? I'm curious as to the clutch switch. It sounds like the compressor is disengaging. The AC system is still running, which technically pulling the amps, but blowing warm/hot - not cold. This leads me to think the compressor clutch has disengaged and may be could have a temp control in the compressor to protect the pump. Or... the alt isn't pushing enough current at low rpm to hold the clutch coil.

Granted, your engine coolant temp is not going up, but under the hood temp is likely spiking in traffic. You have EFI, so set your screen/monitor to display MAP and air enrichment % so you can get a feel for changes the EFI is doing to accommodate temp. I would bet that when you get into traffic MAP will go up and your air enrichment % will drop dramatically (assuming you've tuned that into the ECU). Something to think about concerning air intake and temp sensitive items under the hood.

Also, note the alternator is not going to produce the level of volts and Amps at idle/low rpm. You should have a test sheet for your alternator that will provide you the production to RPM curve, with the installed pulley. You'll likely see a much lower output at low rpm. I'm going back and forth if it's an alt issue - because the fan is still blowing. HOWEVER... the AC comp clutch demands a lot of stable current... soooo... that's a real potential, and that would completely be an alt issue.
 
1-Common sense tells you the problems. A/C works when air is forced through but not at low speeds. Test the pressure it will be high and the system is not performing due to low air flow. Not rocket science.
2-You are not charging properly. Fix that and your problem with the A/C may be fixed.

Question why do you have 3 fans?
 
pnora said:
1-Common sense tells you the problems. A/C works when air is forced through but not at low speeds. Test the pressure it will be high and the system is not performing due to low air flow. Not rocket science.
2-You are not charging properly. Fix that and your problem with the A/C may be fixed.

Question why do you have 3 fans?
Click to expand...
1. you are very right, but also at low speed my voltage is dropping bellow normal, so its 2 things happening simultaneously low voltage and low air flow, so it could be both, thats why asking =)
2. yes, new alternator (165 amps) already in the basket.
3. 2 pullers for radiator and 1 pusher for an AC, why? i have seen some has 4 on this forum, 2 for ac and 2 for rad. i live in a very hot climate.
 
Doorkicker said:
Can you share the name and model # of the AC compressor? I'm curious as to the clutch switch. It sounds like the compressor is disengaging. The AC system is still running, which technically pulling the amps, but blowing warm/hot - not cold. This leads me to think the compressor clutch has disengaged and may be could have a temp control in the compressor to protect the pump. Or... the alt isn't pushing enough current at low rpm to hold the clutch coil.

Granted, your engine coolant temp is not going up, but under the hood temp is likely spiking in traffic. You have EFI, so set your screen/monitor to display MAP and air enrichment % so you can get a feel for changes the EFI is doing to accommodate temp. I would bet that when you get into traffic MAP will go up and your air enrichment % will drop dramatically (assuming you've tuned that into the ECU). Something to think about concerning air intake and temp sensitive items under the hood.

Also, note the alternator is not going to produce the level of volts and Amps at idle/low rpm. You should have a test sheet for your alternator that will provide you the production to RPM curve, with the installed pulley. You'll likely see a much lower output at low rpm. I'm going back and forth if it's an alt issue - because the fan is still blowing. HOWEVER... the AC comp clutch demands a lot of stable current... soooo... that's a real potential, and that would completely be an alt issue.
Click to expand...
i will check map and air enrichment next time! didnt pay attention.
yes, amp is not keeping up, i bought it before i switched to EFI and electric fans, so obviously im now pulling twice as much or even more!
let me check my compressor model, i guess my body mechanic just put one from another car
So its UP-150 from Toyota
UP150 | UPF150 - Unicla
 
Since this is an AIR CONDITIONER question...... what are the readings on your high and low sides ?
 
Just going thru a bit of your challenge on a brand x car, no AC. Installed kit with fan and aluminum rad. with a stock , undersized amp alternator putting out 13.56 volts. On first test run fan ran for a 15 minutes straight and the Chinese fan burnt up, fried, motor melted and locked up in place. Put in an OEM fan I KNEW was good and it also overheated and stopped on a 15 minute drive. I then upgraded to a 100 amp alt. that supposedly moves up closer to 30-40 amps at idle. Voltage went to 14.38 at idle, and it all works as designed. I think underamped really can heat up the fan motors, and with two fans, you need plenty of juice. And then you add compressor current load, much more heat load to the rad
 
Installing/reading the gauges will tell if compressor is engaged and running. If the high presssure keeps climbing as the ac stops cooling, likely heat is building up at the condenser. That says not enough heat is being removed to make it operate possibly.

That alternator is two small for what your doing, sensitive parts will not last long. Get it upgraded.
 
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Curiousyellow71 said:
Installing/reading the gauges will tell if compressor is engaged and running. If the high presssure keeps climbing as the ac stops cooling then heat is building up at the condenser. That says not enough heat is being removed to make it operate, or possibly overcharged.
That alternator is two small for what your doing, sensitive parts will not last long. Get it upgraded.
Click to expand...
just ordered 165 amp one, will that be enough?

fully agree on what you are saying, i guess i have combination of the problems, small alternator and not proper cooling of the condenser. Condenser is still oem, fan i took from another car, but it might be not enough as well, i better upgrade both of them, any recommendation on the condenser and fan amp draw i should be looking at?
 
Make sure the wiring is upto the task.
The A/C condenser needs air flow to work. Hopefully having full power to the fans will fix the problem.
You didn't mention if this is a one wire or a external regulated alternator?
Also, do you know the pulley ratio? A underdrive (small) crank pulley will reduce the alternator RPM and the alternators will not output as much power at low RPM.
 
I looked up the compressor and rated clutch draw... and it's pulling (likely) 20+ amps. With two fans on and at idle... the clutch is giving up... IMHO.
 
mouserider said:
just ordered 165 amp one, will that be enough?

fully agree on what you are saying, i guess i have combination of the problems, small alternator and not proper cooling of the condenser. Condenser is still oem, fan i took from another car, but it might be not enough as well, i better upgrade both of them, any recommendation on the condenser and fan amp draw i should be looking at?
Click to expand...
165amp is definitely an improvement. See if you can't get the test report with the curve. I think this will be your fix.
 
Best have gauges on their before you start guessing on the ac. With the voltage being so low... Install the alternator upgrade first.

Aftermarket fans almost always say cfm and amp draw. Oem fans is harder to find anything.

The condenser should be up to the task if its has air flow. I would look at a condenser for a aftermarket ac if you want a newer one.

165 amp should work.
 
Curiousyellow71 said:
Best have gauges on their before you start guessing on the ac. With the voltage being so low... Install the alternator upgrade first.

Aftermarket fans almost always say cfm and amp draw. Oem fans is harder to find anything.

The condenser should be up to the task if its has air flow. I would look at a condenser for a aftermarket ac if you want a newer one.

165 amp should work.
Click to expand...
alternator is ordered(month of waiting now)
for the condenser fan, what would be a good AMP draw ? (i measure fans by amp draw, not CFM, because all manufacturers lie about CFM, i bought SPAL fan for my Jaguar for 150 backs, its twice more expensive than other chinese fans on amazon , draws twice more current, but has twice lower CFM rating, guess who is right)
 
Doorkicker said:
I looked up the compressor and rated clutch draw... and it's pulling (likely) 20+ amps. With two fans on and at idle... the clutch is giving up... IMHO.
Click to expand...
A clutch will not draw even close to that. Most likely less than 5 amps.
 
mouserider said:
alternator is ordered(month of waiting now)
for the condenser fan, what would be a good AMP draw ? (i measure fans by amp draw, not CFM, because all manufacturers lie about CFM, i bought SPAL fan for my Jaguar for 150 backs, its twice more expensive than other chinese fans on amazon , draws twice more current, but has twice lower CFM rating, guess who is right)
Click to expand...
I would guess a single fan would beed to be close to 20 amp. If you were running two maybe 15 each for a total of 30 amp.
I would agree a lot of electric fans are total crap. Generally you can tell the quality by the price.
 
I have bought several Be Cool fans, and they were Spal fans with hardware. Listed cost was about the same, but Be Cool had a rebate at the time.

Dakota digital had a fancy programable fan controller with blue tooth if you need to control 2 fans at different temps.
I used the older non-bluetooth version before installing the EFI that controls the fans now.
 
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