[Chris65LeMans]

I went for an Easter cruise with the kids today, and ran into a strange issue.

The kids love cruising with the windows down, so I turned on the heater. From a stop sign, the motor started sputtering and popping out of the tailpipes. I turned around to head home, and found that it ran fine with the blower motor off. We continued our cruise, and I confirmed that the motor had trouble accelerating when the blower motor is running at any speed.

My car has:
New M&H under dash harness installed in the last year
DUI HEI
A new (4 months or so) CVF Racing serpentine system with their 140 amp 1-wire alternator. (overkill for my car - I don’t have a/c or even a radio.)

Any ideas? (it just popped into my head) The new alternator is anodized black, so I’ll be checking tomorrow to make sure it’s grounded properly.

Thanks, and Happy Easter!

[Rocco Testa]

It may be a Vacuum leak Which would make sense. When you call for heat it pulls vacuum from the motor. (Engine) If a line is broken or off it would have a vacuum leak and run ruff. Check your vacuum

[Chris65LeMans]

I will, but it runs fine when I have the heat levers turned on. It’s only when I turn the blower motor on that problems arise. Where should I check for vacuum leaks?

[dataway]

Check to see what happens if you turn the lights on with no blower motor, then what happens with the lights on AND the blower motor.

If the lights cause a problem also that would probably indicate a system wide low voltage issue. If the lights have no effect I'd guess ignition switch or something in the fuse box connections. On a 68 at least, the blower motor is driven off a fuse buss that also provides power to the ignition switch acc position ... not the same fuse, but a group of fuses powered by the same buss. On the schematic I see one wire to the blower motor, one to the radio, one to the ignition switch accessory position.

Might want to pull a few fuses in and around the blower motor fuse and check for corrosion, bad connection etc. Might be some minor arcing disturbing the power to the ignition.

Not sure if this applies to a 65.

[hobbygto65]

Check the ground on your blower motor. Possible it could be trying to feed back through your ignition or taking power away from it.

[Chris65LeMans]

Originally Posted by hobbygto65

Check the ground on your blower motor. Possible it could be trying to feed back through your ignition or taking power away from it.

Do you know where the blower motor is, or where it grounds? That’s going on the list. I do have the service manual, but that’s clear as mud at times.

[steve25]

It sounds like your electrical system is being pulled down when you turn on the blower motor with its high current demand, in which case turning on the headlights with the brite's on should have the same effect.

Your firewall mounted regulator or the alternator could be the cause of the issue here.

[JSchmitz]

Did you run a 12 volt keyed wire to the HEI? The factory distributor wire only provides 9 volts. I would check the voltage with key on and not running, key on and running, key on running with blower running. I chased a high RPM miss on my car for months. I had checked the voltage at the distributor off and had 12.5 volts. I didn't check it with the engine running. Eventually checked it with the engine running and had like 6 or 7 volts. I ran a new wire from the fuse box. Car ran better than it ever had!

[steve25]

Voltage testing power to the Dizzy is a full on waste of time with a voltmeter if the motor is not running!
A test meter needs to only be able to pull some .005 amps of current to get a reading , but the HEI or even a points type needs at least 1000% more current!

[JSchmitz]

Originally Posted by steve25

Voltage testing power to the Dizzy is a full on waste of time with a voltmeter if the motor is not running!
A test meter needs to only be able to pull some .005 amps of current to get a reading , but the HEI or even a points type needs at least 1000% more current!

It is not a waste of time. It's a basis for comparison. And it only takes a few seconds. If it's low static there's no reason to check it running. If it's low running you're next step is going to be static voltage checks anyway.

[TAQuest]

Use the IGN prong in the fuse box for your HEI power.

[STEELCITYFIREBIRD]

Originally Posted by JSchmitz

It is not a waste of time. It's a basis for comparison. And it only takes a few seconds. If it's low static there's no reason to check it running. If it's low running you're next step is going to be static voltage checks anyway.

I agree

My thoughts, Firstly the blower should be fused or breaker ed, pull that fuse and see if you still have power to the blower low and higher step to full,(I believe high fan has a separate power supply thru a relay, lower speeds thru blower resistor) then check if the dizzy has power.
This would be to verify the blower is using the correct circuit and if they are sharing their power source(I don't believe they should). Just re seating the fuse may be your high resistance dropping voltage, no rusty fuses or terminals! Reseating the engine main harness connector may be the problem location, but you should verify the the problem area before muddying the water.

It ran correctly as wired last season? If so likely a poor connection dropping voltage, or possibly a weak battery. Start at the battery and verify no load voltage and running voltages. ~12.6(full charge) no load, running will vary depending on battery state of charge and electrical load.

Have a diagram? Would allow a more logical approach at the diagnosis.

[64speed]

You dont have a vacuum leak. Our heaters are cable controlled not vacuum. There is no vacuum hoses anywhere in the system like later cars

[TAQuest]

Once you get that HEI on a proper power source then the problem with the heater fan is that three speed resister or the blower motor windings.

[Chris65LeMans]

Thanks, all. To clarify, I’ve driven the car 12,000 miles in the last 5 years, and this is the first time I’ve seen this. “Regular” HEI upgrade to a DUI was a few years ago. Didn’t have this problem after replacing the under dash harness (and fuse box) last year. Don’t remember if I ran the heater since replacing the alternator a couple of months ago. (Good chance I did.)

I upgraded to a (different) one wire alternator a few years ago and deleted the firewall - mounted voltage regulator.

[77 TRASHCAN]

One of the things I've read here, is to run a ground wire from the alternator directly to the battery, if you use a 1 wire alternator...In Jim Hand's book, he ran a ground wore from one of the vacuum advance screws on his HEI to the battery. I have not done the dist wire yet, but plan to, AND plan to ground my alternator, also...

[Chris65LeMans]

Spent some time this morning on diagnostics.

1. Blower motor doesn’t run when fuse is removed - ok
2. Battery is 12.3 volts at rest. When running, it’ll approach 13.1- probably too low. Numbers are unchanged when I run the blower motor.
3. Alternator seems to be properly grounded. Adding a temp. Ground wire to it doesn’t change results at the voltmeter.

I’ve put the battery on a trickle charger to see if that helps things. Battery is anO’Reilly’s house brand (“smart Start” or something like that), and is a few years old, so it could need replacing.

Next up is to measure volt readings at the HEI. What’s the best way to do that?

My kids have the day off school today, so I’ll get back to it tomorrow.

[77 TRASHCAN]

13.1 is NOT enough...and if the battery is getting weak, those 2 things are not good..

See if HOReillys has a volt meter to use at their store. Drive car there...a thought, if you do not have one. There is an adapter gizmo that plugs into an HEI, then you plug your harness onto it to diagnose stuff. Brand name is Thexton. Someone else may make one...

[Lee]

- Where does the blower motor power wire connect to?

- Where does the HEI power wire connect to?

- How did you change the wiring when you deleted the external regulator?

For 140 amps, you really need about 6ga. wire feeding off of the alternator power terminal. 8 ga. at a minmum.

If you reused the factory wiring off the alternator, you may have cooked some of the wiring. If it is anything like a '67 that I recently worked on, then there are a group of several wires that spliced together about a foot or so away from the alternator - various power supply wires for the car. High amps, undersized wire, old wires and connections... I'd cut open the harness at that location and check the condition.

[STEELCITYFIREBIRD]

Yes your running voltage is too low. Is that an above idle reading?
Now why?