Vacuum erratic when electric fans turn on

[forestb]

Originally Posted by pjmoreland

When the engine is running and the fan is on, do you get the same voltage reading at the red wire on the back of the alternator as you get at the distributor bat+ connector?

EDIT - I skimmed through all of the posts on this thread. Did you take RustyPile up on his offer for a phone conversation? Is your distributor voltage still jumping around? How is the power wired to your distributor? If you follow the wire from your distributor to the location where it ties into electrical system, is the voltage jumping around at that connection as well?

I have not checked my voltage at the alternator with the fan running. When the fan is not on I am reading 14.7 volts at the alternator and 14 volts at the distributor bat+ connector.

No I have not taken rusty pile up on his offer yet. I was afraid that by the time I finished talking to him he would have me rewiring my entire vehicle

I am assuming that when you are referring to my voltage jumping around you mean when I said that it goes down to 3 volts and then back up t around 14 and back down again and that you are not referring to the drop when the fans come on. I think it was because I was not finding a good ground with the negative probe.

With all that being said, my voltage at the distributor is not still jumping around.

My distributor wire connects to the plug in back of the ignition switch. I have not tested the voltage there. I should. That my be a good indicator as to whether the purple wire spliced in from the AC is causing the voltage drop at the distributor bat+ connector.

I am sorry to say that I will not be able to do any of these tests until Saturday.

[pjmoreland]

If I were you, I would not pass up an offer like that for one-on-one help from a highly knowledgeable and experienced person.

If you get a different voltage reading on your alternator vs. the BAT+ connection on your distributor while the engine and fan are running, then that indicates there may something wrong with your distributor wiring.

It sounds like your distributor power wiring might be a bit of a mess. I suggest purchasing and installing the distributor power wire shown in this thread:

https://67-72chevytrucks.com/vboard/...d.php?t=708975

[forestb]

Originally Posted by pjmoreland

If I were you, I would not pass up an offer like that for one-on-one help from a highly knowledgeable and experienced person.

If you get a different voltage reading on your alternator vs. the BAT+ connection on your distributor while the engine and fan are running, then that indicates there may something wrong with your distributor wiring.

It sounds like your distributor power wiring might be a bit of a mess. I suggest purchasing and installing the distributor power wire shown in this thread:

https://67-72chevytrucks.com/vboard/...d.php?t=708975

I guess Painless Wiring is not as painless as the name implies.

I will take a look at the link when I get some time. Thanks.

[forestb]

I read through that link.

In post #121 I posted a photo of the plug that connects to the back of my ignition switch. The pink wire that comes out of that plug goes directly through the fire wall and is connected with a crimp connector to the red wire that goes into the bat plug on my distributor. I am not sure what good the harness mentioned in that thread would do except perhaps increase the gauge size of the wire that is there now. But maybe that is the problem. Not a big enough gauge wire. I think I definitely need to investigate the purple wire from the AC that is spliced into the pink wire.

[pjmoreland]

Originally Posted by forestb

I read through that link.

In post #121 I posted a photo of the plug that connects to the back of my ignition switch. The pink wire that comes out of that plug goes directly through the fire wall and is connected with a crimp connector to the red wire that goes into the bat plug on my distributor. I am not sure what good the harness mentioned in that thread would do except perhaps increase the gauge size of the wire that is there now. But maybe that is the problem. Not a big enough gauge wire. I think I definitely need to investigate the purple wire from the AC that is spliced into the pink wire.

My main concern is that I don't trust splices like the ones shown in your photo. I have found them to be flaky. When possible, I try to wire things the way they were wired from the factory. That link demonstrates a clean way to wire the HEI using the factory connection point and using wire size and crimps that would be found on a newer vehicle that came originally with HEI.

[forestb]

Originally Posted by pjmoreland

My main concern is that I don't trust splices like the ones shown in your photo. I have found them to be flaky. When possible, I try to wire things the way they were wired from the factory. That link demonstrates a clean way to wire the HEI using the factory connection point and using wire size and crimps that would be found on a newer vehicle that came originally with HEI.

I don't trust that splice either. I have to look into a better way to connect the purple wire to my ignition switch. As far as factory style of wiring goes my truck is a 62 and doesn't have any type of firewall plug like the one in the thread. Maybe at some point it did bit it does not now. That splice was added by the mechanic that installed the AC at a later time than the wiring harness was.

[pjmoreland]

Oops. I made the assumption you had a 67-72.

If I had to make a splice, I'd strip about half an inch of insulation off both wires, twist the bare strands together and solder them. Then I'd cover the splice with heat shrink.

[forestb]

Does it matter if I have a ground from the block to a bolt in the frame and then from the same bolt one to the cab? Or is it better to have 2 completely different grounds? That is one from the frame to the block and another from the cab to the frame

[68post]

Originally Posted by forestb

Does it matter if I have a ground from the block to a bolt in the frame and then from the same bolt one to the cab? Or is it better to have 2 completely different grounds? That is one from the frame to the block and another from the cab to the frame

If all the connections are clean it will not matter.

[forestb]

So I am not sure if this is related or not but I had the engine running today and the fan was turning on and off like normal with the temperature of the motor. Then I took it for a drive in the rain and the traffic was stop and go because of the rain and I noticed that the temperature kept climbing and the electric fan was not coming on. I got home without it overheating thanks to the weather and the traffic lightening up. When I got home and looked under the hood to make sure everything was connected okay I disconnected the fan’s wire from its thermostat and grounded it to the manifold to see if it would turn on. In order to test and see if it might be a fuse or if the fan died itself. When I did this I heard a rapid ticking noise. I reattached it to the thermostat and it still made the same noise. My only thought is that water got into the plug that comes directly out of the fan. It is not very insulated from the weather. Maybe it got wet and is causing the relay to to crazy. The plug has the main power wire and the ground.

[forestb]

On another note when I test my volts at the distributor wire using a multimeter the reading has once again started jumping all over the place. This was before I had the problem with the fan. The multimeter works fine when testing the battery and the distributor.

[pjmoreland]

Sounds like you need to do some work to weatherproof your fan relays and wiring. Maybe something like this would help. I don't know if this specific relay has an adequate amperage rating for your application.

https://www.summitracing.com/parts/p...SABEgIyYvD_BwE

If your distributor power wire voltage is jumping around again, then this is an opportunity to do some investigating. Is your distributor power wire spliced into the harness at the ignition switch? See if the voltage is jumping around where it ties in too. Hopefully you will find a flaky connection that needs to be redone.

[forestb]

Thanks for the link but the relay is already one of those weather proof types. It is the plug that I am more worried about. I am going to try try an dry it off and see if that was the issue. Good idea about using this as an opportunity to see if the voltage is also jumping around at the ignition switch.

[forestb]

So the fan started up just fine. The plug must have dried out. I should probably relocate the plug and add some kind of plug weather protection. It is in a vary vulnerable position.

So I was able to get a proper reading from the distributor. I guess I was not stabbing it into the plug far enough. I did do some more tests.

It read at the distributor
13.8 with fan on and the purple wire that is spliced into distributor wire were it plugs into the ignition switch unplugged.

13.8 with fan on and wire plugged in

14.1 with fan off and wire plugged in

14.1 with fan off and wire unplugged.


Distributor wire where it plugs into the Ignition switch

14.1 with both wire unplugged and plugged in with the fan on.

14.3 with fan off plugged in

[pjmoreland]

What gauge is the wire running to the distributor?

[forestb]

It looks like the wire going into the distributor is around 10 or 12 gauge. It is the wire that came with the new plug. But I think it gets smaller when it attaches to the wire that came with the painless wiring harness. It is the pink one in the photo. What is the best way to figure out what gauge a wire is? I would guess around 16 gauge.

[pjmoreland]

If it is fat compared to most of the other wires in your truck, then it is probably good. How and where does the Painless wire going to your distributor connect to the pink wire from your ignition switch?

[forestb]

I have not followed it completely but inside the engine compartment the 2 wires are crimped together. I don’t know if it goes directly from there to the ignition switch or goes somewhere else first.

[forestb]

I should also test to see if other locations on the vehicle loose voltage when the fan turns on I think I heard that the headlights are a good place to check but my headlights have relays so I don’t know if that is a good location.

[pjmoreland]

A quick Google search indicates the optimum range for HEI is 12 - 14.5V. You are well within that range, and the voltage isn't jumping around the way you though it was previously, so it seems unlikely to me that the distributor voltage is the source of your engine idle being affected when the electric fans turn on. I suggest you reread the first few comments at the beginning of this rather long thread and investigate the suggestions made there.

[forestb]

Are you referring to the comments about using three wires instead of one at the alternator?

[forestb]

I don’t known if this matters but tested the alternator with fan on and off and battery with fan on and off

14.5 fan off 13.9 fan on at bat
14.7 fan off 14.5 fan on at alt