greasy

One of my relays is working one is not, that is I get power when the "wait to start light" comes on the rear one towards the firewall.

The other relay (the forward one) isn't sending power thru it even though the little plugs on top are hot and the battery supply side is also hot.


I'll assume it's bad...

What does this heater relay power exactly? Should the little plugs on the top remain hot all the time when cold out? Just turning on the key not starting engine.

Should I just replace it with a cheapo relay like a ford starter relay? If so then do I wire both plugs together?

torquefan

It's quite common for one of the relays to fail. It's the contacts that fail, so even though the relay is working electrically, the current isn't going through. I always get the factory replacements from Dodge- both relays come together with the bracket. I prefer the clean "factory" look. I wouldn't wire both grids together with one relay. The reason is that the PCM cycles one relay at a time for the post heat cycle. Both at the same time would be hard on the charging system when the truck is running.

chop342

They cycle on independant control specs or parameters one may cycles and one may not depending on ambient air tem.

Chris

~Angry Tractor~

I used Ford starter relays on mine. It was suggested by Infidel. They only cost about $7.00 and I think they are better. Ask for the older model ones. They look just like the OEM ones but they are bigger.

greasy

I didn't mean wire everything onto one relay

On the forward most relay there is two small wires with plugs on them that snap onto the top of this relay along with the two heavy leads. If I am not mistaking a Ford relay only has one small wire to activate the relay.

My question was, do I wire both of these small wires together?

if the OEM ones arn't too much I think I may just go with those and mail order them. I'm stuck at work and cannot make it to a parts store

torquefan

No, you don't want to wire the wires together, as one is power and the other is ground. I would have to look at a diagram to remember the specifics of that circuit before I could comment further.
The Ford relays may be slightly better than the OEM preheater relays, but I have never seen an OEM relay cause trouble before 120 000 miles, so it's not a big issue.

greasy

The can't be both ground, I used a tester light and both showed positive hot.
edit: Or my ground wire wasn't working ??? and it was pulling ground thru my tester? I'll check this further when I get home.

In case others are looking at this problem the OEM part number is 56026842
Wholesale $53.13. If you call your local dealer they'll charge $72.00. I'll mail order it wholesale.

took me a bit to find it on the net, I think I'll just order the OEM replacement. They come in a kit and it replaces both relays together

infidel

It depends on whether you buy a Ford relay with a grounded body or not. Ungrounded ones have two trigger terminals. Later CTD model years use a ground signal to trigger the relay, positive is always on, on these you have to use the two terminal type. On a '95 just making sure the relay base is grounded is good enough.

~Angry Tractor~

I just asked for the relays for a 1979 Ford. I looked at my old 79 Ford and it had two terminals so thats what I asked for. $14 and change for the pair. Can't beat em.

GAmes

The leads are always hot. The PCM provides the ground while the heater grid is cycling. I wired my grounds to a toggle switch so I can turn them on or off manually. My reasoning is that once the engine is running there is no benefit for the grids to cycle on.

infidel

Not always, depends on the year.

GAmes

He said "even though the little plugs on top are hot and the battery supply side is also hot."

greasy

also said I didn't start the engine, I was just cycling the pre-heaters on and off to find the problem.

I think the 79 ford ones will work, cheap I like. I used to use them all the time for running big KC daylighters

GAmes

Was it necessary to turn the ignition key on and off to keep power to the relays? Even without starting the engine the PCM will cycle the grid heaters off.