Dang, this morning I spent an hour calling different business trying to find the Bosch 75 amp relay. No one has it, I even tried a trailer parts wearhouse and they did not have it.

Finnaly I ordered one from Wiring Products in Sparks Nevada. $31 plus 5.95 shipping. I will eventually pick up the other material that will be needed.

 

You can get them from most Heavy Truck Parts but defiantly don't go to the dealer, when I ask the guy at the parts counter for a 75-amp relay he said you must have a Freightliner.

A quick search on e-bay,

http://cgi.ebay.com/ebaymotors/BOSCH...Q5fAccessories

There is also a 50-amp and a 70-amp relay that is physically the same size as the 30/40 relays except Term.#30 & Term.#87 are 3/8" spade instead of 1/4"

Don't forget that any Bosch relay that you get will be Old Stock, the new name is Tyco
Jim

 

Jim, if you don't mind a couple more questions. I am working on a schematic for the modification of my 93.

1 How many amps does it take to close the 75 amp relay? I want to put a small in line fuse between the relay and the ignition sw. I just skimmed through the information on the relays and did not find that information.

2 while I am in there is there any other circuit in the truck that is supplied from the ignition switch that needs to be put on a relay?

I may go ahead and do what some of the other guys have done and put the head lights on a relay. I kind of like the high and low beams being on at the same time.

 

Bumb to top for now.

 

I am finnaly getting around to changing the heater circuit but have ran into a problem that maybe you guys can help me with.

I want to connect the wire,a #10, to supply power from the battery to the fuses that are in the fuse block, that in turn provides the power to the blower and AC unit. The tab in the fuse block that the Black/red wire connected to measures 5/16 of an inch wide.

So far all I have done in looking is making phone calls to parts houses but so far I can not find a female connector that will fit the 5/16 male tab.

Any suggestions as to some where I might find the wire connector?

I want to use the fuse block fuses to protect the heater/AC circuit.

 

No ideas here? I am sure some of you have had this problem before.

 

Charlie,

You had to make me go back and look at my pictures to see what I had done, I used a pair of snips and trimmed down the edge so I could fit a .250 or 1/4" female spade terminal on mine, also the terminal that I used was a 10-gauge High Temperature terminal used in HVAC and appliance repair, I use them when I repair air conditioners and electric ranges they will not loose their tension if they get hot.

Also I used a 6-gauge wire to the battery and it is switched with a 75-amp Bosch relay, the now disconnected 12-gauge black/red wire now triggers Term #86 of the 75-amp relay.

You can get these terminals at any HVAC supplier or Grainger’s alternately you can use a 3/8" female spade connector, they are available at most auto parts, they will be carded and hanging with the rest of the terminals.

They were most famously used on Volkswagen voltage regulators and will also fit standard headlamp terminals.

You could also carefully drill a hole and secure a ring terminal using a small 6x32 screw and nut.



This is what the 3/8” terminal looks like, I use these when I design this 70-amp relay into circuits, hard to believe this will switch 70-amps.



Jim

 

Wow. I think I have learned more about wiring from Jim Lane than I have in my Engineering Circuits class that I took last year in college.

 

Thanks Jim.
I looked all over Medford today for the 5/16 wire end to no avail, just not there. So this is what I am going to do, try your suggestion about using a small bolt and ring. Tonight when I got home I looked at the bar in the fuse block and I believe that I can get a 6X32 screw in there.
If that will not work,than I am going to pull the heater blower wire out of the fuse block and connect the blower wire to the wire coming from the relay.

I will add a fuse at the connection and label it so at some time in the future I will know what it does.

 

Thanks for your input Jim. I got the job done and it appears that it is going to work. I will give it a work out tomorrow and know for sure.
I just opened up the hole that was in the orginal spade and as you suggested used the 6X32 screw.

 

Hi Jim
Sorry to hijack this thread but I didn't know where to post this.

I have read this post with great interest.
I have a 1995 motor home with the old Chrysler Slide Action Dash Control panel. And a Evans Tempcon A/C unit.

I am having a problem where with the fan on high speed it intermittently stops and starts.

I have changed the fan switch, resistor and the fan with no change. I have also changed the relay on electric AC condensor fan. The dash fan was bad for a year or more before I changed it. This problem existed before I changed the fan.
My unit does not have a relay for the dash fan.

Do you think by adding the relays as you have illustrated in this post it could fix the problem?
　

Here is a link to the schematic for my unit. Mine is wired like the "Typical Midway and High Performance Stacked Coil Wiring Diagram" on page 2

http://www.evanstempcon.com/pdf/scs/...schematics.pdf

thanks