Seems the ASD relay has been accused of being the culprit in a lot of 'no start' issues lately.

I remember back in the day how mysterious this little black plastic box seemed, until I opened it up. It was not the easiest to open. I used a small drill bit on a slow setting to remove a large portion of the white plastic tabs which held the internals inside the black plastic. A little bending prying and pulling is necessary to get it completely apart.

This is from my '89 b250.



I opened mine up, because I was having a hard time finding a replacement, and when I did, they wanted 30+ dollars and it would take a couple days to receive it.

I found the contacts which close internally when 12 volts are applied were crusty. I cleaned them off with some 400 grit wet dry sandpaper, and the relay worked. 6 months later it stopped working again, and I jumped the 2 fatter wires on the connector which correspond to tab 30 and tab 87 to drive home.

When I opened up the relay again, I found the lead/tin contact point had basically fallen out of the copper. I removed it the rest of the way, and bent the copper tabs so that they touched cleanly when the 12 volts was applied.

It has worked fine for 3 years now.

Tab 30 should receive battery voltage (+)from the corresponding tab on the connector.
Tab 87 goes to whatever device this relay is powering, in this case the fuel pump
Tab 85 is ground(-)
Tab 86 is the ignition feed. When you apply 12 volts to 85 and 86 the magnet inside closes the contacts allowing battery voltage from tab 30 to flow to tab 87.

Seems most all relays work very similar to this. My ASD relay powers not only the fuel pump, but fuel injectors and ignition coil according to my Factory Service Manual

For those that see errors or can add or help clarify to this post/ thread, please chime in, or PM me to fix any inaccuracies.

If this info helps you please let us know the circumstances so it can maybe help others.

 

It's a useful post LY. I too wasn't sure how relays worked until a month or so ago when my remote start/locks stopped working. The two relays that locked/unlocked the doors was a completely sealed unit (until I cracked it open). It was 'just' two Bosch bog standard relays as you describe above. Basically the remote start applied a short 12v signal to either one and it fed 12v from battery to the door solenoid. Both relays 'clicked' but didn't connect 30 to 87 so you need to use a multimeter to test connectivity.
I must admit I blow a few fuses figuring it all out but that's what fuses are for right ?

Some relays have double pole i.e. 87a and 87 get connected to 30 when 85/86 have juice just be careful and make sure you understand what your relay does.

 

Where is this located at????

 

On my '89 it is located to the right of the brake booster on the firewall, at about 4 oclock.

 

Looks like a common SPDT relay.
$30 is ridiculous for a $3 part w/ a fancy fat back plastic case.


I use 40a ones all day long here at the shop for car audio installation.
I bet $1000 to a donut you could just pick up a normal 40a SPDT relay at a local parts house for $3-5 and it will drop in place.

 

This.

 

When you say local parts house, do you mean Autoparts stores? Because I was in several yesterday browsing the electric sections and saw nothing like it, but did not ask at the counter.

I guess as long as that middle contact does not interfere with installation it would work just fine.

Fairly recently I found the contacts in my power door lock relay were crusty, and opened that one up and cleaned them, now the locks clunk open or closed with authority.




I doubt this relay could be easily or cheaply obtained, but 5 minutes and a little 400 grit makes that unnecessary.

 

If the center contact might be a problem, you could use a SPST relay. They do not have a center contact, pin87a.

But what you posted in the pic that looks like it is from a manual, is a SPDT relay. (has pin87a) It just has a different shaped plastic case, the internals and pins are the same.

 

I had these relays on my Ford Explorer and they lasted about 3 years before the points in them would fry. They were used on the fuel pump circuit. They may be rated for 30 amps but I doubt they can handle that much current as they get older. I found I can whack the top off using my scroll saw, file the points then glue it back together.

 

Can someone please tell me which of the relays on the firewall is the ASD Relay. There are two side by side but I don't know. Great picture and information but I don't want to tear apart the wrong one. 95 Dodge Van Mark III conversion 5.2 V8.
My issue I think is power flickering on and off really fast making the relay jump...check engine light flickers...doors lock themselves...engine stalls and then wont start...fuel pump wont run. Its tough to reproduce so that's why I'd like to rule out the ASD Relay. Also I've looked all over for a reference to the relays online. There are a bunch of them under the hood and I have no idea which one is for what. :|

Thanks