i have a 90 f150 with a 4.9, i had to jump the pressure switch to get the pump to come on, should the pump still cycle with the switch bypassed like it is, and also how cold should the air be blowing inside its cool but i dont think its as cold as it could or should be i have put about a can and a half in it so far started to rain so i stopped, also should the clutch be drawing alot of current casue when i turn it on the volt gauge drops way down. thank in advance

 

If you had to jumper out a pressure switch, there is a problem. Probably not a bad switch, but likely undercharged. Have the system checked.

 

when i origonally tried to charge it the pump wouldnt come on no matter how long i let it set with the can on it but when i unplugged the pressure switch and jumped it it started right up, and has now takein a charge of about 1 1/2 cans of r134a each can being 13ozs, now im just trying to figure out if itll should be cycleing on and off with the switch being jumped out and how cold it should be blowing, yeah i know i probabley should have replaced it first but ill change it later

 

Check your high side pressure if it is to high it high pressure cycle switch will cut the compressor normal high pressure is 225 to 250.

 

There should be a sticker on the a/c system somewhere that tells what type of freon the system uses and how much (i.e. 2.75lbs, 3.lbs etc). It sounds like you may not have enough freon in the system yet, but it doesn't explain the cycling compressor when jumper wire is attached. I would make sure you have the right amount of freon (use the pressure recommendations given) and then see if it will run on its own.

 

i do remeber seeing some wheres on the truck that it takes r 134a so thats what i put in. the pump doesnt cycle with the wire jumped, should it be thou? also i dont have any gauges to measure the pressure in the lines, but im gonna try putting some more in later today, im gonna see if the pressure switch will work before i put any more of a charge in it

 

The switch is what causes the compressor to cycle. Before adding refrigerant, you should have had the pressures checked with the switch jumpered. The systems that used R12 originally (a 1990 vehicle probably did), may have 2 pressure switches, one on the high side and one on the low. Without knowing which one you have jumpered, its difficult to determine what's happening there.

 

i jumped the low pressuer switch, i hooked the switch back up today after i finished putting the second can of 134 in it, its blowing fairly cold inside now so i think it has enough in it now but the low side switch doesnt work

 

Can you be more specific on the low side switch? If it is blowing cold air on the inside than the compressor must be running, and the compressor wouldn't be running if the "low pressure switch' wasn't working. Do you mean the low fan position on the (inside) switch by chance?

 

the low pressure switch on the acumlater, i unpluged it and jumped it out with a wire to get the compresser clutch to engage and circulate the refrigerant, also after putting the rest of the second can in the system it is blowing colder, it just doesnt cycle it stays on all the time, maybe caseu i have the pressure switch jumped?

 

Yes, if you have the switch jumped then it will run continuously and not cycle. If you plug the switch back in and it cycles, thats ok. It doesn't always cycle at the same rate, it depends on things such as outside temperature, but the cylces tend to be a little shorter as the system fills. If you take out the jumper wire and plug the switch back in, and the compressor doesn't run at all then you have a bad low pressure switch. When you jump the switch, it allows you to pump freon in until the pressure is such that it allows the low pressure switch to do its job. You may be there.

 

i hooked the pressure switch back up and at first it did nothing, so i tapped it afewtime with a screwdriver and it kicked on, i shut it off and tried again nothing had to tap it and it came back on, shut it off again and it started on its own, so no more jumper wire to have the ac working, the only thing it didnt seem to be cycleing

 

Without knowing the actual pressure, I would say that you may want to put a little more freon in it and it may run without tapping on it with the screwdriver (assuming your tapping on the compressor). Don't worry about the cycling because it knows when to do it itself (i.e. based on temp. and all). Again you might want to look for the system capacity and you might find it close to three pounds, if it is that is APPROXIMATELY three cans.

 

ok went outside and looked on the acumu;atoer found the label i said it takes 3lbs 4 oz of r-12, but it has been converted to 134 it has the fittings for 134 just not the label, so it should still take 3lbs right, in that case i probabley need to put in a little bit more

 

Yes, changing the type of freon doesn't change the capacity. Also, keep in mind when older systems are converted to 134, they don't always get as cold but should be mighty comfortable.