Q I’ve replaced the single electric fan on my ’55 Chevy that was activated by a toggle switch with dual electric fans that are controlled by a Dakota Digital PAC-2750.
The car has Vintage Air and was equipped with a trinary switch with four connections—two for low/high pressure and two to turn the fan on with the A/C on.
I’ve been told that I have to change the safety switch to the binary type that just protects the
A/C system because the PAC-2750 operates the fan according to engine temperature and when the A/C is turned on.
I’m hesitant to change the switch because that would mean draining the A/C system and then recharging it. Can I keep the switch I have, and if so, which wires do I use? H.Pertroski ViatheInternet A According to Scott
Johnson of Dakota
Digital, either a binary or trinary switch will work with the PAC-2750. When using a trinary switch only the high/ low pressure protection function is required, as the PAC-2750 will control the fan(s) by tapping into the power connection that feeds the compressor. That 12V signal provides a trigger engaging the fan(s). Johnson added that because the A/C activation function of the PAC-2750 input is simply looking for the presence or absence of power to the A/C compressor clutch that wire could be repurposed as a fan override switch for those without A/C.
Johnson provided the following wiring diagram that shows the use of a trinary switch with the PAC-2750. Note the color of the wires to be used on that switch are both black with a green stripe. The other two wires are not used.
Tech, Trailers, and the Occasional Wise Crack
Q I’ve been reading
STREET RODDER for over 20 years. I’ve followed the tech stories faithfully and used many of them to build cars over the years. I always start at the back of the new issue. The first thing I read every month is your column, then Ron Covell’s, then Brian Brennan’s editorial, then everything in-between. It’s always amusing when he takes a shot at you and you make a crack about him in a story.
A number of years ago you did a story on building an affordable car trailer. I would like to copy what you did but have not been able to find the issue where it appeared. Can you tell me when that story was printed? C.R.Bond ViatheInternet A Thanks for sticking with us for all these years and giving me the opportunity to point out to Brennan that you start at the back of the book and work your way forward.
The trailer story was some time ago; it appeared in the July ’09 issue. While somewhat of a departure from the traditional tech stories, we figured that many street rodders would be interested in an affordable car trailer that was easy to build. The only drawback to owning your own trailer is all your friends who don’t have one will want to borrow yours.
Our trailer used a simple angle iron frame and wood decking. We added a toolbox to hold tiedowns, a winch for loading nonrunning projects and an electric tongue jack to make life easy. The loading ramps were made from some discarded catwalk found at a scrap yard; they’re stored in a recess in the deck. Loading and backup lights come in handy and casters keep the tail from dragging on steep driveways.