Air Conditioning/Cooling Fan Cycling

Created: 6/11/97

Last updated: 3/30/02

Author/source: Carollo/DML (Courtesy Luke Sandel) Additions by DMCJoe

Date: Wed, 11 Jun 1997 16:15:03 -0500 (CDT) From: delorea1(AT)
(MICHAEL K. CAROLLO) Subject: DML: Jim Senft, air conditioning problem

There are two items to look at when diagnosing this problem:

1. If you have updated your relays, then you need to make sure that you have replaced the two circut breakers that are included with the kit with the current flowing in the same direction as the older breakers have. The wires from each side of these breakers is not interchangable. If you have mixed up the wire connections, then the breakers become overheated and will cycle the cooling fans because they are overheated. A good clue that you have this problem is to check and make sure your fans cycle as they should when your engine temperature is calling for the fans to cycle on and cool the radiator. If you are not having a problem overheating when you run the air than this probably is not your problem.

2. There is a low pressure switch located on the passenger side of the car, mounted on the dryer assembly of the air conditioning. If you turn your front wheels all the way to the left you will be able to access this switch without jacking the car up. Behind the left front wheel is the dryer/switch assembly. There is a three prong plug that is attached to this switch. Pull it off and underneath is a fitting that can be moved with a pair of needle nose pliers either clockwise or counterclockwise. This switch controls the cycling of the air conditioning compressor based on the low side pressure of the air conditioning. Start rotating the switch in slight increments until your cycling starts to extend to what is recommended in the Delorean manual. My manual indicates that the cycling time should be between 45 and 90 seconds. This time will be dependant on ambiant outside temperature and humidity at the time you are trying to adjust this switch. If by adjusting this switch you cannot adjust the cycling time you should consider replacing this switch. It is very inexpensive, 12 to 24 dollars and since this is a Harrison system, many GM autos of the Delorean vintage use the same switch.




SOME LATER INFORMATION: - I'd suggest that you deal with an experienced A/C repair person before trying this. There seems to be a difference of opinion on the process.


From: "Walter Coe" <

Sent: Friday, March 29, 2002 8:46 PM

Subject: Re: DMC technical section

The problem with the technical article is that it recommends a cycling time of from 45 to 90 seconds, and this is just completely wrong -- not even close.  This is fine for many GM and Ford systems, but the DeLorean cycles at about 7 to 11 seconds.  The recent discussion on the DML was about a guy who was trying to adjust it according to the article.  DMC Joe had some things to say about it being wrong also.

If you want to keep the article up there, how about adding the post from DMC Joe confirming what is wrong?  Below is Joe's posting:

From: "DMC Joe" <>
Sent: Saturday, March 23, 2002 12:20 AM
Subject: Re: [DML] A/C cycling switch

I would like to add that the statement you quoted from the article that said "if adjusting the switch makes no difference then you should replace the switch". This is completely wrong.

The AC Cycle Switch, which is correctly named the Low Pressure Cut Off Switch, is factory calibrated and the adjustment should not be tampered with. Excessive cycling of the AC compressor is almost always caused by an insufficient level of R-12. As Walter said the engage or "on" time of the compressor should be no less than 7 seconds with the engine RPM at 3000. If you have tampered with the switch you should replace the switch and add freon until the compressor cycles within the above mentioned time period,


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