Contour Enthusiasts Group Archives Forums General Troubleshooting A/C and cooling fan

When I turn on the A/C the cooling fan is suppose to come on and stay on constantly as long as a/c is running well mine does'nt when I turn a/c on the cooling fan will come on the go off.IT will come on when the high side gets to about 320 to 350 then the pressure drops down to 230 and fan shuts off then pressure goes back up to 325 fan comes on agin,It just keeps doing this as long as a/c is running.If you turn a/c off fan works normal only comes on when the temp gets up there.Whats the deal here can you help.I just had the compressor and orfice tube replaced but it did it on the old anyways so that does'nt have anything to do with it.Please help before it get real hot around here.

From '98 service manual:

High pressure switch


The function of the high pressure switch is to protect the high pressure section of the refrigerant circuit. When pressure exceeds the maximum value of 2965kPa (430psi) because, for instance, the air flow through the condenser is impeded or the high pressure line is blocked, the high pressure switch switches the compressor off.

Only when the pressure has fallen once more to 2241kPa (325psi) bar is the compressor switched on again. At a pressure level of 2241kPa (325psi) the PCM switches to high blower speed.

Only when the pressure has fallen once more to 1717 kPa (249 psi) does the PCM switch to low blower speed.

I dont understand?My cooling doesnt just change speeds it shuts off.While the a/c is on my cooling fan will cycle on and off on and off about every 40sec it will it will cycle off then about 40sec later it will come on agin.I doest change speeds it will shut off completly.Now it is suppose to stay on constantly right as long as a/c is on fan should be on.

It sounds like the low speed function of fan is not being controlled by the PCM as it should be, but instead by the high pressure cutout switch. That switch is intended as a redundant safety measure to keep the system from exploding/discharging from excessive pressure.

Have the fan control system checked by somebody who understands it if you aren't certain as to how it works. Avoid using the A/C system in the meantime until the primary problem is repaired.

If you have a meter and a schematic, the circuit isn't that difficult to diagnose and I can walk you through it.

Steve

Oh I think I know what your trying to say.Your saying that when my ac is turned on and the fan kicks on to bring the high prssure down it then should kick to low speed till prssure goes back up right.And mine when it suppose to kick down to low speed does not it just quits till its time for the high speed agin.Is that right.If you could tell me how to check that I can have my dad he's and Electronic tech.And works for a Gm dealership he's always testing eletrical stuff.I dont know if i stated it but this car is a 96 2.0 liter DOHC I also have a ford service manual on it.

Tell him to dig out the ETVM.

Look for the output of the PCM that energzes the low speed relay. Turn ignition on. Using a flexible jumper wire, ground that pin of the relay - the relay and the fan should turn on. If it does, the problem is PCM related. If not, check the relay and the fan dropping resistor that is between the relay and the fan(s).

I don't have a 96 service CD but I do have the 95 and 98 ones. Your circuit is probably very similar if not the same.

Steve

Bad cycle switch on the low side will kill the low fan too. One needs the diagrams to know what to jump out to test it. Cycle switch has two pins so that is a no brainer to jump out. The high pressure/high fan switch can be jumped out if you stay with the colors. The fan in is black with white stripe which goes to ground lead black. Circuits are designed to kill the system if one of the components is out. The EEC picks this up and shuts stuff off.

Okay guys I will print this out for my dad to read.Thanks for the info.IF you come up with anything else please let me know.

His cycle switch is working as shown by the pressures he posted. If it weren't, the clutch would never engage.

Steve

Well my dad took that relay out and jumperd across and the fan would not come on.One side was hot which I belive would have been the pcm side and we jumperd to the fan side and it would'nt come on.I cant remeber why but he said that the resistor is bad he tested a buch of wire's and said that the resistor is not working.THe only problem is we could not find the resistor and ideas where that resistor is.