mwpayne

My 74 temp sensor (the one just under the t-stat) is bad, and I'm on the lookout for a replacement. I'm guessing one from an RX-4, 3, or maybe an SA would work, but not sure.
It's primary function is to allow the choke to release upon warmup...mine never does. Would one of you old school gurus happen to know if one of the other models would work, or perhaps another replacement?

Thanks!

Jeff20B

iTrader: (13)

Short the leads in the rat's nest side of the connector. If that does not cause your choke holder to hold, you have other problems. The dude in the waterpump might still be good.

mwpayne

Did that, that's how I narrowed it down to the sensor. Also, I pulled the sensor out and hooked a meter to it while immersing it in hot water. No change in resistance. Once I pull the plug, the choke lets go.
I can put a switch on it, no biggie, I'd just like it to work.
I don't have a sensor in my waterpump at all..I don't think. I'll crawl under there and make sure.

kansei

iTrader: (3)

Jeff means the very sensor you are talking about. It is located in backside of the water pump housing.

Your problem likely lies in the Thermosensor located on top of the center housing. It was only on the '74 models and ultimately controls the choke release. They are prone to going bad when they get this old. Mine did the same thing.

Neal.

Jeff20B

iTrader: (13)

I forgot about that sensor on the intermediate plate. I simply blocked mine off with a cover plate.

mwpayne

I have the sensor on the top of the center housing, it doesn't seem to do anything (rats nest removed, maybe it's function was related to that?), but it does change resistance when exposed to hot/cold water, so I believe it works. When it's unplugged, it affects nothing engine wise, however.
Just for giggles, I tried swapping the connectors on the thermosensors, didn't help my problem.
The only thing that affects my choke release is unplugging the sensor just behind/on the thermostat housing..that's why I thought it was the problem. Also, it is for sure not working, at least when exposed to hot/cold.

So, that sensor has nothing to do with the choke?

Jeff20B

iTrader: (13)

All I know is the way to test that your choke holder is actually working, is to short the two wires and see if it holds the choke ****. If not, something else is wrong. If so, the choke switch in the back of the waterpump is bad.

I just use a penny these days, or keep my foot a little on it during the first mile as it warms up.

kansei

iTrader: (3)

Mike,

If you know the water temp sender in the backside of the water pump housing is bad, then get a new one from the dealer or Mazdatrix and replace it, then work from there. Why are you trying to track down other problems, when you already found a primary culprit?

All I can tell you about the thermosensor on the intermediate housing is that mine went bad, and although the temp sender technically let the choke release, the truck would not idle properly after the choke released with the thermosensor in-op. It is tied into the choke circuit and fast-idle circuit. I don't remember exactly how it affects idle and all, as it was about six months back when I sat down with the factory WSM and wiring diagrams to track down my problem. Since your thermosensor is apparently OK, swap out the temp sender and call it a day.

Neal.

mwpayne

Dealer was NLA, haven't tried mazdatrix, though. I'll probably throw up a pic to make sure we're all on the same page regarding the sensor I'm talking about.
I was assuming that old sensor wasn't to be found anywhere, that's why I was trying to find a replacement. It's the cause of my one choke not releasing issue, I'm sure. Idle, all else is fine.