Our new Trailer 1975 Scamper

Zacvv wrote:
Hello,

I have found out what pump it is im not sure if its very old or not it doesnt look too new but not 1975 old thats for sure
7215 iv peters & russell inc serial 4.71

Not sure if that is enough information

Does it look like one of these? Here is a schematic of the two main styles of PAR pumps.

If you have one of those two and the pump operates good but not with the pressure switch in the circuit, the pressure switch needs service or replacement. If you look at the top of the switch and it has some screws that hold down the top of the switch, it is serviceable.

This will be like rebuilding a carburetor so get a good clean work surface prepared with a rag under everything. Place all removed parts in an orderly line. Take the screws out slowly from the top case side. There is a spring/s inside and they will want to throw off the top. Be careful to keep the gasket in one piece. Remove the case top and spring, any retaining bits, and the wires with their contacts. You should be left with the case and a piston inside a bore. Gently pull the piston out and any relief springs and washers.
The next and primary part of business is cleaning everything up. The cylinder and bore should be cleaned with a weak acidic solution like vinegar or citric cleaner. Also the piston. Note the presence of any O-rings and replace if hard or misshapen. When you reassemble, use some mineral or vegetable oil in the bore and around the piston. I usually use some RTV silicone on gasket mating surfaces to insure water tightness. You can even test the switch by connecting your multimeter to the wires and depressing the piston (if the switch has an exterior rod).

The alternative to servicing the switch is to buy a new pump since all modern pumps have the pressure switch integral to the pump body.