car misses when ac and blower is on

[camoman22]

I have a 1972 satellite sp fractry air. I have this problem with while the ac and blower is running the car misses. I have changed ignition switch,by passed the bulk head with 8ga alt to amp meter the on to battery. It is a voltage drop deal because it gets worse when head lights are on. The coil wire is losing voltage some how. I have a factory wiring Manuel. any Ideals where to look?

camo

 

[Glenwood]

What is the voltage to the coil before and after turning on stuff? Sounds like you voltage regulator or alternator aren't working properly.

 

[BeeKool]

X2
Sounds like a charging issue. Throw a load tester on the alternator while running with everything on.
Load test the battery too with everything unhooked.
Hopefully it's as simple as that.

 

[camoman22]

New alt and reg voltage is a 13.5 but when it misses I see as low as 9 vdc for a split sec. I've not checked the bulk head terminal that feed coil or what else's on that curicut.

 

[Forklift]

The voltage at the battery with a load should be 13.8 to 14.2. I think you have a voltage drop in the ign. wiring. Check the voltage at the coil positive terminal with key on should be full battery voltage. After engine starts should drop to about 6 or 7 volts when engine is running unless a coil with a built in resistor has been installed and the external resistor removed. If the external resistor is still there check there for 12 in and 7 out and that it stays under load.

 

[camoman22]

The voltage at the battery with a load should be 13.8 to 14.2. I think you have a voltage drop in the ign. wiring. Check the voltage at the coil positive terminal with key on should be full battery voltage. After engine starts should drop to about 6 or 7 volts when engine is running unless a coil with a built in resistor has been installed and the external resistor removed. If the external resistor is still there check there for 12 in and 7 out and that it stays under load.

I converted to hei so running full voltage at the coil 13.95 with key on and after start turn air on and blower on high I see a stumble on the meter down to 9vdc at coil for a milsec.

 

[camoman22]

ok I may have found my problem The car started dieseling also and I remember I used a lower octane fuel the last fill up. car was running lean also. filled up with 93 now its running fine. I also think the larger wire from the alt to battery helped to.
To all that replyied THANK YOU this is such a great site.

 

[camoman22]

Hello all its me again....I thought I had this thing fixed but no it's not....
I still have a problem with the car miss firing after warm up when the a/c is turned on. Now the car idles fine when a/c is on but as you give it fuel it pops and cracks 3000 rpm or so.

new 100amp alt
new wires
new plugs
new voltage reg
8ga wire to amp meter 10ga wire to battery
hei ign using mopar dist (all parts switched out from another running car that runs fine)
voltage is a full 13.5 volts at the coil at 3000 rpm but with the a/c on engine it pops and cracks, turn a/c off engine smooth's out perfect. ran a relay with a push button switch to a/c still same results.

Please give me some ideals where else to look.

 

[WileE]

As I've said many times. Check your grounds.

 

[camoman22]

As I've said many times. Check your grounds.

I have checked the main ones maybe missed the one that's the problem.

 

[4spEd]

Fan may be creating electrical noise getting into ignition pickup circuit. I had simmilar symtoms with electric cooling fans. Try and move fan wire circuit away from ignition wires.

 

[camoman22]

Fan may be creating electrical noise getting into ignition pickup circuit. I had simmilar symtoms with electric cooling fans. Try and move fan wire circuit away from ignition wires.

ok I do have an electric fan I am feeding it off the alternator output . That being said I think I am feed the ign module off the blue field wire off alternator. I think... I just jumped ballest resistor wires when I removed it. maybe i'm getting noise feeding the module?

 

[4spEd]

If you can reproduce in driveway by reving it up to 3000 after its warm then i would try moving various fan wires or ignition pickup wires around while its occuring and see if it goes away.

 

[Shorthorse]

Good info all around. Charging, grounds and possible RF interference to electric ignitions are all suspect. What if you just turn on the lights, no AC and/or just the blower motor, no AC? I might have missed it but have you also looked directly at your battery voltage during all this?
I am confused about your wiring the electric fan to the output of the alternator. That post is hot all the time. Does your cooling fan run off a thermostat control that shuts it off? Do you have a working ammeter and does it appear to look like everything is OK?
Maybe someone else would know for sure but I think the electric cooling fan draw would not be sensed by the voltage regulator when connected at the alternator output.

 

[camoman22]

Good info all around. Charging, grounds and possible RF interference to electric ignitions are all suspect. What if you just turn on the lights, no AC and/or just the blower motor, no AC? I might have missed it but have you also looked directly at your battery voltage during all this?
I am confused about your wiring the electric fan to the output of the alternator. That post is hot all the time. Does your cooling fan run off a thermostat control that shuts it off? Do you have a working ammeter and does it appear to look like everything is OK?
Maybe someone else would know for sure but I think the electric cooling fan draw would not be sensed by the voltage regulator when connected at the alternator output.

Shorthorse,
with lights only or fan blower car runs fine and with electric fan blowing. Turn a/c on then it idles a little rough. battery voltage drops at the battery amp gage show this drop
as discharge( low idle ). rev car up to 3000 rpm voltage is 13.5 vdc but engine snaps and cracks turn off a/c smooths out fine.
You are correct about the electric fan thermostatic controlled pulls engine down for a second 45 amp draw then smooths out. amp gage does not show the draw.
Many thanks for your input!
camo

 

[Glenwood]

Sounds like a short circuit. Maybe in the ac clutch?

 

[Shorthorse]

I think Glenwood is onto something. If the absolute only thing that will start your symptom is the AC, then the AC clutch would be the most logical deduction. However, one thing still doesn't make sense. If you have 13.5v at 3000 rpm's, then you don't have a voltage issue. I could see it if you dropped at 3000 rpm's but you don't. Very confusing! I'm starting to think it might be that RF thing again. Maybe you could temporarily ground the AC compressor body and/or its mounting bracket. Is there any chance you could throw your old ignition back in? Also, make sure any ignition wires are separated and not bundled with or near any fan or AC wires.

 

[camoman22]

I think Glenwood is onto something. If the absolute only thing that will start your symptom is the AC, then the AC clutch would be the most logical deduction. However, one thing still doesn't make sense. If you have 13.5v at 3000 rpm's, then you don't have a voltage issue. I could see it if you dropped at 3000 rpm's but you don't. Very confusing! I'm starting to think it might be that RF thing again. Maybe you could temporarily ground the AC compressor body and/or its mounting bracket. Is there any chance you could throw your old ignition back in? Also, make sure any ignition wires are separated and not bundled with or near any fan or AC wires.

OK , I have changed compressors saden type no change . Old ign is a no go. one thing I have not tried is the 12v power wire that supplys the new ign module is fed off the blue field wire from alternator .
I'm thinking that maybe when the a/c is turned on it pulls a load on alternator which causes RF
through the field wire . will check this asap.
camo

 

[idrivemopar]

I don't know about 72, but in 73 the blue wire fed the voltage reg, ignition, ac compressor, choke and carb solenoid for when the ac is on.

You said your fans are directly connected to the alternator, is that the field wires or main output? Either way, try switching its feed to a battery side of the circuit instead of the alt output and see if that fixes things. Or what happens when you run the car with the fan disconnected and switch on the ac, do you still have the same issue?

 

[camoman22]

I don't know about 72, but in 73 the blue wire fed the voltage reg, ignition, ac compressor, choke and carb solenoid for when the ac is on.

You said your fans are directly connected to the alternator, is that the field wires or main output? Either way, try switching its feed to a battery side of the circuit instead of the alt output and see if that fixes things. Or what happens when you run the car with the fan disconnected and switch on the ac, do you still have the same issue?

The fan is on the main feed of the alt. here's more info I found out tonight.
it is a rf spikes I'm almost sure. It only misfires when under full load fans ,lights and a/c .Checked coil voltage during misfire and voltage stayed 13.34 volts no drop. Turn headlights off runs fine. So I ran wire from battery to coil. started car turned all things on and it ran fine. so now what?