79 Mercury Zephyr

[sly]

Yeah... I should wire in the e-fan to the PCM in my 93, but since I already have the high side setup (PCM uses low side) using a temp switch, I don't feel like messing with it until something dies, just like you did.

[massacre]

Yeah... I should wire in the e-fan to the PCM in my 93, but since I already have the high side setup (PCM uses low side) using a temp switch, I don't feel like messing with it until something dies, just like you did.

Forgive my ignorance, but what do you mean by high side and low side?
Thanks

[sly]

Whether the electronics are switched from positive or ground side of the load. Ground side would be low side switching and positive is high side switching. Ford likes their low side drivers in their electronics (switch is at the ground). This is why you have power to all of the devices (ie: injectors, coils) and the switching done (PCM) is done at the point it goes to ground.

[massacre]

Whether the electronics are switched from positive or ground side of the load. Ground side would be low side switching and positive is high side switching. Ford likes their low side drivers in their electronics (switch is at the ground). This is why you have power to all of the devices (ie: injectors, coils) and the switching done (PCM) is done at the point it goes to ground.

Ok thanks, that is what i thought you meant.
Interesting you brought this up, i usually wire my relays with a fixed ground, and triggered by 12v signal. But the holley directions said to wire the fan relay so that it is ground triggered instead. Same way the OD shutoff switch and indicator are wired. 12v to relay at all times, ground activates relay. Different then what i'm used to but i mean it's a relay, not a spaceship lol.

[sly]

Pretty much. Just move the switch to the other part of the circuit using common power instead of common ground.

[massacre]

Pretty much. Just move the switch to the other part of the circuit using common power instead of common ground.

In your opinion, is there any advantage either way? I feel like high side switching is easier/better since there is not a constant switched 12v signal required.

[sly]

In my opinion, high side switching is better for high voltage or Alternating current setups since it keeps the dangerous potential voltage disconnected until in use. For lower voltage DC (like automotive), low side switching actually works better since it requires less circuitry in the chips that do the work. The only reason I know this is because I work for a semiconductor manufacturer and work on these automotive parts every day. The high side drivers are MUCH more complicated. The low side drivers are extremely simple in comparison. The issue is that the switching voltage (using a relay as an analogy - think of the coil as the switching side and the power in and out to the device as the switched side) has to be higher than the switched voltage to actually do the switching. Low side drivers don't need higher voltage. Grounding the input turns it on when dealing with a p-gate FET. This is why a lot of enable pins on chips are triggered low. Low side drivers use a basic 3-12V input structure and internal inverter to basically a p-gate to switch power. It's very simple compared to the high side driver than needs a charge pump to increase the input to over 20V to trigger the high side to open.

[massacre]

In my opinion, high side switching is better for high voltage or Alternating current setups since it keeps the dangerous potential voltage disconnected until in use. For lower voltage DC (like automotive), low side switching actually works better since it requires less circuitry in the chips that do the work. The only reason I know this is because I work for a semiconductor manufacturer and work on these automotive parts every day. The high side drivers are MUCH more complicated. The low side drivers are extremely simple in comparison. The issue is that the switching voltage (using a relay as an analogy - think of the coil as the switching side and the power in and out to the device as the switched side) has to be higher than the switched voltage to actually do the switching. Low side drivers don't need higher voltage. Grounding the input turns it on when dealing with a p-gate FET. This is why a lot of enable pins on chips are triggered low. Low side drivers use a basic 3-12V input structure and internal inverter to basically a p-gate to switch power. It's very simple compared to the high side driver than needs a charge pump to increase the input to over 20V to trigger the high side to open.

Thanks for the info, very interesting! Never really thought about it in that way. Much appreciated.

[packman]

Was having some weird overheating issues, nothing too bad just had to pull over and wait. Elec water pump was intermittent. Replaced relay and all seems better now. But my elec fan controller shit the bed. It was the flex a lite controller that came with my black magic 185. I was using that instead of the holley just because i had it, it was already wired, and it worked.
So i wired in another relay for the fan, and man i should have just let the holley control the fan from the beginning!
Works great now, funny how i always seem to have the time do do things right the second time! LMFAO

So the Flex-a-Lite fan controllers are not reliable?

[massacre]

So the Flex-a-Lite fan controllers are not reliable?

To be fair, mine is an older model controller. Probably 15 years old or more. I noticed that the newer model controllers are different and more modern, more robust.
Mine always worked fine all that time. A more modern controller may be more reliable than mine was. I don't want to shit on flex a lite, it worked fine for a long time, and it also worked fine in this car as well. Until it didn't.

So i guess reliability depends on how long you expect a fan controller to work. At that time i went with the flex a lite since it was designed to work with the fan and also had a separate manual switch to override the thermostatic switch. It was the way to go back then.
My controller came with the temp sensor metal probe that fits into the fins on the radiator. Pretty outdated tech at this point in 2022.
If i did not have the holley, i would buy a more modern controller and give that a try. The older one worked fine for what i paid for it.
I am looking into a PWM controller to work with the holley to run the fan at different speeds. Probably next year tho since the season is coming to an end here in MA.

[massacre]

Looking forward to getting the Zephyr out of storage soon! The car is an absolute blast to drive! Just so much fun.
I signed up for a Holley EFI tuning class, been learning a lot. Going to start getting deeper into tuning the car. I need to re-scale my oil and fuel pressure sensors, and change some of the transmission parameters.
Also need to get different wheels. I absolutely love the Mark vii wheels, but the backspacing is all wrong for early fox chassis. So need to measure to see what i need to buy.
I ended up buying some of the fender trims and an OEM front fender for the car, and a black carpet, new rear window defroster relay, new headlight aimers.
But need to get some sub frame connectors first thing.
Once i get it back home i'll update the thread.
Thanks for reading

[a_d_a_m]

You know your car better than anyone but in the pictures I've seen, the Linc wheels look perfect on there. Are there any other OE Ford 5-lugs you'd consider?

[gadget73]

If the VII wheels are too far in, Panther wheels are right about an inch and a quarter further out. Same bolt pattern.

[massacre]

I need way more backspacing in the rear to fit some decent width tires. Fronts will rub with wheels turned hard.
Once i measure everything then i'll know which way to go.
I'm not really opposed to any wheels as long as they fit nice and look good.

[massacre]

Took the Zephyr out of storage today.
Started right up and drove 60+ miles with zero issues.
Super happy about that, was a fun ride home