[Squidward]

Not sure how the 65 a/c or heater system works, but the 67 FB system uses a combo of cables AND vacuum to make things work. Not sure if 65 is similar.

The 67 FB a/c system requires the control lever to be in a position other than OFF to run the blower fan. When it is in a non-off position, vacuum will be utilized in 3 of the 4 positions.

I like the vacuum leak model. If you have any type of vacuum supply going from the manifold to the ac/ventilation system, then you can disconnect and plug that line from the vacuum source, and see if your fan running causes the problem.

So... not a 65 guy, so I can't be sure on the vacuum interaction with the vent system. But I'm not feeling the electrical loading model.

[242177P]

Originally Posted by Squidward

Not sure how the 65 a/c or heater system works, but the 67 FB system uses a combo of cables AND vacuum to make things work. Not sure if 65 is similar.

The 67 FB a/c system requires the control lever to be in a position other than OFF to run the blower fan. When it is in a non-off position, vacuum will be utilized in 3 of the 4 positions.

I like the vacuum leak model. If you have any type of vacuum supply going from the manifold to the ac/ventilation system, then you can disconnect and plug that line from the vacuum source, and see if your fan running causes the problem.

So... not a 65 guy, so I can't be sure on the vacuum interaction with the vent system. But I'm not feeling the electrical loading model.

Mine was an A-body, but yeah, the 67s (with AC) used vacuum to operate doors. Underhood actuators become fragile, that's where I'd start looking.

[TAQuest]

Where I would start is to hot wire the distributor straight to the battery. Start it up and turn on the blower and see if anything changes. That would eliminate an electrical supply problem. I bet that DUI is a little 'touchy' with it's power supply.

[STEELCITYFIREBIRD]

The key here, because of the condition that causes the problem is the dizzy voltage, with and without the blower running. You may have a high amp draw from the blower from bad blower, poor or improper connections, or it may be an available power supply problem.

The engine runs off the alternator when running, the battery is a load on the system...bat being recharged. 12.3 is an acceptable static battery voltage.

Where did you grab your running voltage readings/ connection positions?

Is this a one wire alt that requires some rpm to excite the field? ( not sure of how that deals alt output will work), but your running voltage seems low to me.

To Check dizzy voltage,insert + from meter into power wire from the back side of the plug, or pop top off dizzy and check from top inside(better), check voltage from that wire to block key on engine off, running with blower off, and then with blower on.

Inspect the condition of your body ground or if one exists! You can temporarily connect a set of jumper cables, block or bat neg to body...or both.

Definitely check the splice and wiring condition just downstream of the alternator. Make sure + connection is excellent @ alternator. Look for voltage drop downstream of alternator +.

Do you have bolt on battery terminals?
Is main terminal tight @ starter? Are you using 2 or all 3 terminals @ starter?

Again...Got a diagram?

[Schurkey]

Originally Posted by STEELCITYFIREBIRD

12.3 is an acceptable static battery voltage.

NO. A fully-charged battery will typically show 12.6--12.7 volts.

12.3 is at least 1/3 discharged. Maybe more.

Originally Posted by STEELCITYFIREBIRD

Is this a one wire alt that requires some rpm to excite the field? ( not sure of how that deals alt output will work), but your running voltage seems low to me.

Running voltage IS low. Should be about 14.2-ish. In the bad old days, 13.5--15.5 was the rule-of-thumb for mechanical voltage regulators. They'd sometimes be cranked up to 15+ in the winter, and down to 13.5--14 in the summer.

If they were giving away aftermarket "one wire" alternators for free, I wouldn't walk across the street to get one. Nothing but problems including the lack of remote voltage sensing, and the need for excess rpm to "turn on" the alternator.

[Rocco Testa]

Also check by your 3 speed blow resistor. I seen cars were they start to melt and burn and most have been GM cars The colors of the wires should be red and purple and are some what larger then the rest. But your voltage does seem low.

[Chris65LeMans]

I’m not sure if I have a wiring diagram or not. I should still have the under dash one - is that where the blower motor is?

Voltage was tested at the battery, with a voltage meter. No change when I revved the engine (by hand, from the carburetor,) to 2,500 or so.

I unplugged the battery from the tender on Monday. Just went and checked the voltage on it - 12.8.

The suggestion to check the positive wire from the alternator is a good one - I’ll take a look when I get a chance. That’s one of the few parts that was on the car when I bought it, so I don’t know what I’ll find.

Thanks again, all.

[stellar]

I suspect your alternator is of the 10 SI design. Often when alternators are made to a higher amp the output power curve changes dramatically . The high RPM output will be higher, but the low RPM output suffers. It would be great if you would do an amp test of the alternator. A volt test is good, but the amp test along with the volt test would tell a lot more. At 12.3 the battery is low. It takes a bit of time for the volts to rise even if the alt is working, so a quick test doesn't tell much. Retest volts while holding RPM high and see if the reading slowly increases. If the rotor in the alternator is not a special wind or at least a 94 amp rotor the low RPM output will be low. I think a CS 130 alternator would work much better, even a stock 100 or 105 amp unit. These have a very good low RPM output. You may also want to test the voltage at the alternator post. If it is significantly higher than the battery voltage, check the wiring especially at the splice mentioned earlier.

[Lee]

Chris,

I really expect the problem to be at the junction where the power wires meet, wherever that may be.

On the 67 I recently worked on, I found burned insulation, and bare copper that was discolored from heat. And that was with the old externally regulated alternator. A higher amperage alternator will make even more heat.

You probably also should trace the wires to see how the "external to internal" conversion was performed. There could be something funky in there as well.

On the '67 I mentioned, I ran a dedicated 8ga charge wire from the alternator directly to the main terminal at the starter. The other wires that had previously connected to the charge wire (the burned/discolored wires I mentioned above) were cut back to where there was good wire/insulation, connected to another 8ga wire, and that wire was also routed to the starter.

I made the power post of the starter into the power junction for the electrical system. I also popped the plug out of the "1-wire" alternator, so that it would operate as a 3-wire, and routed the sensing wire (#2) to the starter terminal as well.

If you rewire, then I suggest getting some good GXL or TXL wire, not the cheap stuff from the local parts store. I recently bought a bunch of GXL wire from wirebarn.com I would at LEAST use 8ga, and some charts show to use 6ga for 140 amps. Wire Barn is also on eBay, their store is https://www.ebay.com/str/wirebarn


Here is a nice calculator, to help determine proper wire size for the amperage and wire length: https://www.wirebarn.com/Wire-Calculator-_ep_41.html

[goatman1970]

Now is probably a good time to remind everyone, unless your classic car is a daily driver, you should keep a battery tender on it full time, only take it off when you drive it, put it back on immediately when parked. This will keep that battery alive for nearly forever. They only cost about $10 at Harbor Freight, best investment you'll ever make.

[Chris65LeMans]

I checked the positive wire coming off the alternator, and it is HUGE. The battery has been on a tender since, and I took a short drive yesterday. (detailed the car for the start of the local cruise-in’s season this Friday I’ll test the heater again then.

[Schurkey]

Originally Posted by goatman1970

Now is probably a good time to remind everyone, unless your classic car is a daily driver, you should keep a battery tender on it full time, only take it off when you drive it, put it back on immediately when parked. This will keep that battery alive for nearly forever. They only cost about $10 at Harbor Freight, best investment you'll ever make.

Until crappy Communist electronics overheats and burns down your garage.

No way in hell would I leave cheap Chinese electronics unattended for long.

[64speed]

A 65 a body has no vacuum components in its heater system

[Bentwheelbob]

Originally Posted by Schurkey

Until crappy Communist electronics overheats and burns down your garage.

No way in hell would I leave cheap Chinese electronics unattended for long.

A good friend of mine had that exact thing happen in December 2017 with a $10 Harbor Freight tender. Hooked it up to his wife's Mercedes as they were departing for their annual 4 months in Florida. They were 6 hours into their trip when a neighbor called and said their house was burning down. Damage exceeded $300,000 and the Mercedes wasn't covered because he paused his auto coverage on it since it wouldn't be driven.

[Schurkey]

Originally Posted by Bentwheelbob

A good friend of mine had that exact thing happen in December 2017 with a $10 Harbor Freight tender. Hooked it up to his wife's Mercedes as they were departing for their annual 4 months in Florida. They were 6 hours into their trip when a neighbor called and said their house was burning down. Damage exceeded $300,000 and the Mercedes wasn't covered because he paused his auto coverage on it since it wouldn't be driven.

I guess illegal Chinese lead-based paint is conductive.

[242177P]

Originally Posted by 64speed

A 65 a body has no vacuum components in its heater system

[torqhead]

Originally Posted by Chris65LeMans

Voltage was tested at the battery, with a voltage meter. No change when I revved the engine (by hand, from the carburetor,) to 2,500 or so.

Chris, This is your problem. If you only have 13.1 volts no matter if you rev the motor your alternator is not charging properly. When you turn the blower motor on, the power draw is pulling it down enough for you to experience your misfire issue. As Steve said earlier, turn your bright headlights on and chances are that will cause the same problem although the blower fan probably pulls a lot more power than headlights.

[Chris65LeMans]

Originally Posted by Bentwheelbob

Damage exceeded $300,000 and the Mercedes wasn't covered because he paused his auto coverage on it since it wouldn't be driven.

Excellent cheapskate move there. "Going on vacation for 4 months - gonna save $200 by cancelling my car insurance."

[64speed]

If your car has ac it may have vacuum components but if not it doesnt

[track73]

Originally Posted by Chris65LeMans

Excellent cheapskate move there. "Going on vacation for 4 months - gonna save $200 by cancelling my car insurance."

You can keep your fire and theft when you suspend your insurance coverage. It's pretty cheap.I blame the insurance agent.