[DML] Re: Question about Air Conditioning cycling
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[DML] Re: Question about Air Conditioning cycling



Thanks for the replies to my cycling concern.

I have the Fan Fail Fix 2x2, and upgraded breakers, so I should be 
in good shape there.  I should probably wait for hotter weather 
before I complain about cycling, becuase the outside temp was only 
in the mid to high 60's when I encountered the fast cycling.  I 
suppose I should wait for an 80 degree day and see what the cycle 
time is then.

Paul


--- In dmcnews@xxxxxxxxxxxxxxx, "Harold McElraft" <hmcelraft@...> 
wrote:
>
> I see numerous responses to your concern. The one thing you should 
> definitely be concerned with is the frequent cycling of the 
cooling 
> fans. This could lead to an over heated fan circuit stopping the 
> fans and causing engine over heating.
> 
> Unfortunately the fans are designed OEM to cycle precisely with 
the 
> AC compressor. I say unfortunately because if the AC system does 
> become low charged or develop another issue to cause rapid cycling 
> of the compressor, the fans will rapid cycle too when you have the 
> AC on. The cycle of the fans with the AC compressor is completely 
> independent of the otterstat used for engine cooling although the 
> fan circuits for both are integrated starting at the circuit 
breaker.
> 
> The fans are what I would call "utility" quality. They are 
designed 
> to work in extreme conditions - to do this, their design is 
anything 
> but efficient. To start each fan requires 20 amps + or - a few 
> depending on the condition of the fans and the electrical system 
> connections, grounds, etc. This compares to 11 to 14 amps to run 
> each fan once started. As the saying goes - "you do the math". The 
> constant starting of the fans is extremely hard on all components 
of 
> the circuit and soon leads to a failure of the weakest part in the 
> circuit - usually the OEM circuit breaker (a 35A standard duty 
> circuit breaker with "pressed" connections) or the OEM blue module 
> (notorious for poor quality inside) or the single relay (20/30 amp 
> rated ? that means 30 amps start 20 run). If you beef up one 
thing, 
> another component will soon fail ? maybe in flames. BTW the motor 
> will be the last thing to go in my experience.
> 
> All of this has been the topic of discussion ever since the 
DeLorean 
> was introduced. As new in Houston (where I started 1982), a daily 
> driver soon experienced "fan fail" and eventually, virtually 
> everyone did.
> 
> So, what to do? My suggestion is have the AC shop do a full 
service 
> on the AC system including replacement of the orifice tube and 
> accumulator. Alternatively, as a minimum, have them do an 
evacuation 
> and refill with the proper amount of gas (say 2 to 2.25lb of 134 
> gas ? AZ 2 lb NJ 2.25 ? just my approach). A proper functioning AC 
> system will cause minimum cycling of the AC compressor and 
therefore 
> the least amount of stress on the cooling fan circuit. I still use 
R-
> 12 (2.25 ? 2.5 lbs of gas)
> 
> Next, get one of the vendors' fixes for the cooling fans. Zilla is 
> by far the best vendor package offered in my opinion ? I have no 
> idea if you can still get one. Or, get Hervey's set up from 
SpecialT?
>  the Dual 2X2. Or, install the DPNW modification (the least 
> expensive but effective). I'm not a big fan of the wire jumper 
> modification unless you replace the under-rated relay (Hervey may 
> still have the higher rated ones ? 30/40).
> 
> Last, be sure all connections for the fan circuit are checked and 
> clean ? especially the grounds attached to the frame on the front.
> 
> Another BTW - the rapid cycling is usually an indicator of low gas 
> or a restricted system (probably at the orifice tube). Normal 
> minimum cycling on a cool day is probably off and on every 5-10 
> seconds - on a hot day cycling could range from 30 seconds to 
> rarely. To get an AC system to function correctly takes the 
correct 
> tools and a knowledgeable technician with the correct specs.
> 
> Harold McElraft - 3354
> 
> 
> 
> --- In dmcnews@xxxxxxxxxxxxxxx, "sweetp01569" <paul.sweet@> wrote:
> >
> > While my car was in getting lowering springs and shocks done, I 
> asked 
> > the mechanic to check out the AC.  He said it seemed to work 
fine. 
> it 
> > blows cold air and is not leaking anywhere.  However, the 
constant 
> > cycling of the cooling fans worries me.  The fans will stay on 
for 
> only 
> > two seconds, and off for about 5 seconds, on and off on and 
off.  
> > Wouldn't this cause excessive wear on the fans to energize them 
> every 5 
> > seconds, and they only stay on for 2 seconds?  It doesn't seem 
> right.  
> > The cycle tiem seemed to be longer last year when I had it 
charged 
> in 
> > August.  I have the R134 conversion.
> > 
> > Thanks,
> > 
> > Paul
> >
>










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